Timing belts are a part we love to hate. They put a very real deadline on the life of your engine unless you spend many hours changing the timing belt; fail to do that in time and your machine is likely dead. But if you thought regular timing belts were bad, you haven’t met the disastrous technology of wet timing belts. They’re the ire of Europe, in particular, and they’ve won many enemies over the last two decades.
I’d never heard of wet timing belts until I came across this video on YouTube. What I found shocked me. The concept is simple enough: just build an engine where the crank pulley for the timing belt is actually in the oil bath of the sump. It’ll get nicely lubricated and run smoother and quieter, with a minor improvement to efficiency, which everybody loves. All good, right?
Well, reality has proven that’s not always the case. Wet belts have become a bugbear for many owners and mechanics. It’s one of those cases where many wish automotive companies had just stuck with the old way of doing things. They’re not just as bad as traditional timing belts—they may, in fact, be even worse. All thanks to one unexpected failure mode that can really ruin your day.
Why Use A Wet Belt?
The wet timing belt promised multiple benefits over a traditional dry timing belt. Lubrication from the engine oil was supposed to reduce wear and noise. More importantly, though, it reduced friction, which would provide an efficiency benefit, with fuel savings of around 1%.
The first mainstream engine that boasted a wet timing belt was the Ford 1.8-liter TDCI turbodiesel, as seen in the Ford Mondeo and Transit Connect. The original version of the engine used a timing chain from the crank to the diesel injection pump, and then a regular dry timing belt from the injection pump up to the cams. However, in 2007, Ford changed all that, using a wet timing belt to replace the timing chain. Traditionally, automakers had recommended that timing belts should never come into contact with oil, as it would degrade the rubber of the belt. However, these belts were manufactured out of special Hydrogenated Nitrile Butadiene Rubber (HNBR) that was more resistant to heat and oil, and also coated with Teflon for added resistance.
By design, the lower timing belt would come into contact with oil at the bottom of the engine. The wet lower belt was supposed to actually last longer than the upper dry timing belt, since it had the benefit of lubrication. Ford quoted a 100,000 mile, 5 year change interval for the dry belt, and a 150,000 mile, 10 year interval for the wet one.
The design quickly spread from there. In 2012, a wet timing belt made its debut on Ford’s 1-liter 3-cylinder EcoBoost engine. Renault also got on board, as did Volkswagen, Peugeot, Vauxhall and Opel. In the vast majority of cases, the wet timing belts were used on small displacement engines of 1.5 liters or less. Almost all are inline-three or inline-four engines.
Why Many Don’t Like Wet Timing Belts
First off, just google “Wet Timing Belt” and you’ll come across lots of stuff like this:
Yes, while there are plenty of examples of wet timing belts working just fine, despite the promised benefits, public opinion on wet belts is largely negative. You won’t find too many people singing their praises, but you can find a lot of gearheads raging against them. The reasons are simple. People are finding that they don’t last as long as promised, and they also introduce a significant additional problem that traditional rubber timing belts never had. We’ll get to that in a moment.
As you probably already know, a timing belt (whether wet or dry) syncs valve movement with piston movement and makes sure the valves are retracted from the combustion chambers as the pistons reach the tops of their strokes to prevent the pistons from colliding with the valves. If the timing belt fails on an “interference engine,” the engine will often die a very complete death as the pistons and valves collide. And so, it’s always wise to follow the manufacturer’s suggested interval for timing belt replacement and thus avoid the costly broken-belt scenario.
The problem is wet belts sometimes fail quite early. Why? Based on what I’ve found around the web, it seems the special compounds and coatings that make the belts more oil-resistant are not actually perfect. In many cases, they’re simply not able to keep a belt alive as long as automakers might have hoped. Sitting in hot oil just isn’t good for belt life, there’s no two ways about it. Using the wrong grade of engine oil or skipping oil changes can also potentially harm belt life. Contaminants in the oil and buildup of acidic content over time could make a difference, here.
This Peugeot engine had a wet timing belt rated for 112,000 miles or 10 years. This belt was looking ragged after just 75,000 miles and 6.5 years in operation.
Replacement is a sizeable job.
Wet belt engines are typically found in small European market vehicles, so dealing with wet belts has become a common problem for European mechanics. These vehicles have also been sold elsewhere, but much of the content discussing wet belt problems comes from Europe and the UK.
For example, it’s easy to find videos on the early Ford TDCI engines from British YouTubers, like this replacement video from mechanic Alan Howatt. “I know a lot of ya have had your engines trashed because these belts have failed,” says Alan. He’s eager to sound the alarm for Mondeo and Transit Connect owners. “I would seriously look into it and have it replaced if it needs doing,” he warns.
More Ways To Die
Even if a belt doesn’t fail, it can harm the engine in other ways. For example, if the timing belt starts coming apart and shedding particles, these can end up blocking the oil pickup, starving the engine of lubrication. This can kill an engine even if the timing belt is still largely intact.
Make no mistake: This failure mode is entirely unique to wet timing belts. This never happened with traditional timing belts because they exist completely outside of the engine’s oil system. It’s a special and terrible feature of the wet belt design. You can find mechanics decrying this problem all over the place.
Yes, it’s really that bad. You don’t just have to worry about your timing belt snapping. You also have to worry about it shedding gunk and cutting off your engine’s oil supply. Instead of just one ugly failure mode, wet timing belts give you two! How lovely.
What Is To Be Done?
Knowing whether your wet timing belt is failing is key to avoiding major engine damage. However, it can be difficult to determine. A visual inspection, if possible, is a good start—if swelling or cracking is apparent, the belt should probably be changed. For Peugeot, Citroen, Vauxhall, and Opel models, a tool is commonly available for checking belts—it’s a simple width gauge. If the timing belt doesn’t fit in the gauge, it’s swollen enough that replacement is indicated.
The belt can be checked in-situ in some engines by inserting the tool through the oil cap.
Beyond that, it’s worthwhile looking in the sump if possible to make sure the engine oil pickup isn’t fouled. Simply changing the oil won’t solve this problem. The debris must be removed from the sump and pickup if present.
It’s difficult to understand why these belt designs even entered production. The benefits seem relatively minor, and the risks seem almost obvious. For my money, as an engineer, I’d speculate that the problems with these wet belts weren’t obvious in manufacturer testing. Automakers might put millions of miles on mule vehicles, but they don’t test a new engine design for five or ten years prior to release. They test on accelerated schedules. There are ways to simulate longer-term degradation and wear, but they’re not perfect. I can only guess that the belts seemed fine, only to start falling apart and causing grander problems when they got out into the real world.
Thankfully, these wet timing belts aren’t everywhere. Japanese automakers largely haven’t touched them, and vehicles with bigger engines have mostly stuck with traditional timing chains or dry belt designs, too. If you do have an engine with a wet timing belt, though, you really need to stay on top of things. Keep doing your oil changes on time, and inspect your timing belt regularly—well ahead of the manufacturer-recommended interval. If it needs changing, change it, and check your oil pickup, too.
It’s just another one of the weird ways automakers have changed vehicles, and not for the better. This happens from time to time, but usually, lessons are learned and things get better again. Here’s hoping wet belts go the way of the PowerShift transmission and cease darkening our engine bays forever more.
Image credits: Alan Howatt via YouTube screenshot, driving 4 answers via YouTube screenshot, Ford
1% fuel economy savings is huge when trying to go from 30mpg to 33mpg to satisfy government regulations. It gets you 10% of the way there before changing anything else. This is what happens when you want to push MPG as far as possible, who cares the cost, or eventual environmental impact of engines turning to scrap in 100k miles.
I had no idea this was a thing. Tbis makes me happy that all four of our vehicles have OHV engines with nice short timing chains. I have a feeling I’ll go straight from those to EVs, and skip all this nonsense.
I will say I prefer dry belts over chains. I recall an engine blueprinting book I have saying they are actually better than chains from a stress/longevity point of view to the engine itself. They cushion some of the forces from combustion better too.
My 1.9 ALH is a belt but my 1.0 Insight is a chain. Having changed both I prefer the belt.
I often find these manufacturers designs work great for regular use but poorly for enthusiastic use. Then the enthusiast confused with an expert argues against it. Then a good idea is tossed because abusers ruined it
We have a ’24 Trax with the 1.2L 3-cyl. Apparently, it has a wet timing belt. But… The stealership where we bought it provided us with the “Warranty Forever” option free of charge for us. So if we follow the rules and have all service done and documented as scheduled, supposedly this third party extended warranty will cover the entire powertrain from the turbo all the way to the wheel bearings for as long as we own it, or until the cost of the repairs exceed the NADA book value of the vehicle..
From the brochure:
ENGINE Engine block and all internally-lubricated parts including the crankshaft, rod and main bearings, cam bearings, expansion (freeze) plugs, connecting rods, engine mounts, torque strut, wrist pins, pistons, piston rings, camshaft, cam tower, lifters, cylinder head, valves, guides and seats, valve springs, rocker arms (cam followers), pushrods, timing chain housing (cover), timing chain and sprockets, timing belt and pulleys, timing belt tensioner, intake and exhaust manifolds, eccentric shaft, flywheel/flex plate, balance shafts, harmonic balancer and retainer bolt, crankshaft pulley, valve covers, oil pan, oil pump and pressure relief valve, engine oil cooler hoses, oil filter adapter/housing, fuel supply pump, vacuum pump, dipstick and tube, and fasteners. Seals and gaskets are only covered in conjunction with the repair of a component listed above.
Turbocharged/Supercharged/Enhanced Engines – In addition the parts listed above, the turbo-charger, waste gate controller, intercooler, hard lines, compressor, clutch and pulley, bypass valve, injection pump, lines, and nozzles.
TRANSMISSION Automatic – Case and all internally-lubricated parts including the oil pump, valve body, torque converter, vacuum modulator, governor, main shaft, clutches, bands, drums, gear sets, bearings, bushings, sealing rings, TV cable, solenoids and electronic shift control unit (internal only), transmission mounts, cooler, cooler hoses and hard lines, dipstick and tube, and fasteners. Seals and gaskets are only covered in conjunction with the repair of a component listed above.
FRONT WHEEL DRIVE Final drive housing and all internally-lubricated parts including the carrier case, gear sets, chain and sprockets, bearings, bushings, axle shafts, axle hub bearings, propeller shafts, universal joints, drive shaft support, front axle hub bearings, and fasteners. Seals and gaskets are only covered in conjunction with the repair of a component listed above.
Car Rental expenses are not covered under the Warranty Forever® agreement. Towing and roadside assistance expenses are not covered under the Warranty Forever® agreement.
If I have all service done at my local stealership, they claim they will take care of all the required paperwork for the warranty. (see below) If the vehicle needs service while we’re out of town, there’s a pretty specific notification process we have to go through to keep the warranty from being voided.
MAINTENANCE REQUIREMENTS You are required to change your vehicle’s engine oil, check and maintain the transmission fluid level (if applicable), top off all powertrain fluid levels and check and maintain the proper level of coolant as follows: Manufacturer Required Synthetic or Synthetic Blend Oil: Every 12 months OR 10,000 miles, whichever comes first. Conventional Oil: Every 6 months OR 7,500 miles, whichever comes first.
MAINTENANCE NOTIFICATION Routine maintenance is critical to ensure optimum performance of your vehicle. You have the option of servicing your vehicle at the repair facility of your choice. Remember, you must notify the administrator in advance of any maintenance performed outside the selling dealer’s facilities so they can keep records of all work you have performed. Failure to notify the administrator will result in a denial of coverage.
THE CHOICE IS YOURS All service records must be filed with the Warranty Forever® administrator to maintain coverage. When service is performed at your selling dealer’s facilities, your dealer will notify the administrator. You may also have maintenance and repairs performed at any other licensed facility, but you must notify the administrator first. Failure to do so will result in a denial of coverage.
HOW TO CONTACT THE ADMINISTRATOR FOR MAINTENANCE NOTIFICATION 1. Choose a licensed repair facility to perform your maintenance. We do not provide a list of authorized dealers, so the choice is yours. 2. Call the administrator at (800) 810-8458 to notify them of the maintenance you are having performed.
YOU WILL NEED THE FOLLOWING INFORMATION DURING THE CALL: Warranty Forever agreement number or last 8 digits of VIN Date of scheduled maintenance appointment Name of the licensed repair facility where you are having maintenance performed Maintenance you are going to have performed Current mileage on odometer Any additional questions you may have 3. Follow all customary maintenance instructions outlined in your Warranty Forever® agreement. You can call our service facility or the Warranty Forever® toll free number with questions or for additional guidance at any time.
So we’ll see how this works out for us.
I have my doubts the numbers will work out in the end, but my biggest concern is that it’ll be easy for the hotline to keep you on hold for hours, especially since you need to notify them before the work is even done.
Well, it didn’t add anything to the cost of the vehicle.
I plan on having all the scheduled maintenance done at the stealership. We only plan on putting a few thousand miles per year on the Trax. If I end up having to plan a trip to an out-of-state Stealership in advance if for some reason it needs service while we’re on a road-trip, I’ll just have to schedule it online with them and make all the calls in advance before we leave. Even if it costs us $100 – $200 more per year to have it serviced at the stealership, hopefully it will work out in the end.
“or until the cost of the repairs exceed the NADA book value of the vehicle”
Will simply having an engine with a wet timing belt affect the NADA book value? Seriously, I don’t think we’ll know that for a few more years.
I find it notable how the extended warranty place requires a “licensed repair facility” for all routine maintenance and service.
By law, factory warranties must allow for DIY work if it is done to spec with appropriate parts and supplies. Third party warranty enhancements and extensions, maybe not so much.
Fuck all the PSA petrols engines
Even the THP has timing issues with its chain.
The French were only ever good at diesels anyway. Now that diesel is (mostly) gone, I don’t think I’d buy any French car with a reciprocating engine.
That’s a bit harsh. My D7F has been perfectly reliable for 200k miles
My money’s on this being a response to government mandated efficiency rules. 1% is meaningless to the individual consumer but it definitely matters to the manufacturer trying to meet ever-stricter standards without losing power which buyer will definitely notice.
1% is about a third of the gain you usually get from engineering a new engine from the ground up for a billion dollars or so.
I’m assuming the reason timing belts are ever used at all is because they cost significantly less than chains. In small economy vehicles I guess that makes sense. Is my assumption correct? Is there any good reason to use a timing belt of any kind (wet or dry) vs a chain or even a gear?
It seems that all of the classic reliable engines use chains or gears. Why stray from that?
My understanding is that, as smaller engines often rev higher than larger, more attention is paid to mass within the rotating assembly. The chain will be slower to rev than the belt.
A timing belt also absorbs vibration and noise, making the engine run a bit quieter and smoother. The fewer cylinders you have, the harder it is to get it to run quietly and smoothly.
Cheaper, quieter, and more efficient. And modern materials mean they’re not that much worse than a timing chain in terms of longevity as long as you don’t run them through a bath of hot oil. Or at least, there’s definitely an overlap between the wear life of the best belts and the worst timing chain tensioners.
I first learned about these wet belts on I Do Cars. On a recent episode Eric tore down a Ford Boost three cylinder. The gross brown color of that belt reminded me of the Jeep Willys’ pressed sawdust/plastic timing gear.
“Timing belts are a part we love to hate.” I do not understand why y’all insist on this narrative. Timing belts are fine and have some advantages over chains. Just change them at the required interval, which means a few hundred dollars and one day at the mechanic every, oh I dunno, 4-6 years. I fail to see why this seems like such a big deal to you. Do you also hate crankcase oil? Spark plugs? Air filters? All things that also need to be changed at regular intervals or else you put “a very real deadline on the life of your engine “
Ford’s current interval for wet oil pump belts is ‘never’. Yeah, right…
It’s the “just change them at the required interval” part that people hate. With prices that are realistically $500-$1000 and a full day at the shop it’s not really a good comparison to oil changes, spark plugs, or air filters that are a half hour job that’s closer to $50. When the alternative is a chain where needing to replaced at all during the lifetime of the car is considered a failure, I can see why people aren’t fans.
Then people should get good with their hands, dry timing belts are not hard to replace on most cars and while a garage will charge you about £1000 you can do it yourself for about £150-200 including an oil, oil filter, water pump and spark plug, change as long as youre driving an aprrox 2010 vehicle. I couldnt change a brake pad 2 years ago when i started driving, last month i pulled the head of my engine off, completely deconstructed it, cleaned every individual part and the head itself, replaced and reseated valves and replaced all the gaskets, im currently about 700 miles in with no further issues. (09 astra h 1.6l I4 petrol) It only cost me £250 total for an erling gasket set £90 1 new valve £10, grinding paste £10, oil £35, coolant £40, torque wrench £35 (for head bolts) and cleaning products. The only expense i spared was the timing locking ruler for the camshafts which i made out of an old grinder key that happened to be a perfect 4.2 mm thickness, a few cuts with the grinder to form the protrusions and voila! a homemade timing ruler that you can slate all you want but like i say, im about 700 miles in and no problems thus far.
The average American’s approach to maintenance seems to be “add oil when the warning light comes on”*
*Based on anecdotal evidence and stereotypes
The issue here is early, catastrophic failure.
“Just change them at the required interval…“
That’s the problem here…these wet belt Ford Ecoboost engines are not surviving as long as Ford told buyers to expect.
https://wheelbasegarage.com/engine-transmission/ford-ecoboost-1l-engine-wet-timing-belts/
A GUIDE TO WET TIMING BELTS FOR FORD ECOBOOST 1L ENGINES
“Regular maintenance of the wet timing belt is critical for Ford EcoBoost 1L engines. As highlighted by Ford themselves, these specialised belts should be replaced every 10 years or 150,000 miles – whichever comes first. As mentioned before, we recommend the wet timing belt to be replaced at no more than 8 years or 80,000 miles and at a recommended 5 years or 50,000 miles, to ensure your engine runs smooth and to prevent any further more devastating issues that may arise from a worn or damaged wet timing belt.”
However, some owners are suffering failure even with all required maintenance performed… and not even reaching that reduced 80,000 mile figure:
https://garagewire.co.uk/news/bbc-watchdog-ford-ecoboost-wet-belt-problem/
One couple spent £15,000 on a four-year-old Focus with 50,000 miles on the clock and full service history. An engine failure left them with a £3,000 bill, which Ford refused to pay because the car had been serviced by an independent garage.
Matt also spoke with Natalie, whose seven-year-old Focus suffered a wet belt failure at 52,000 miles. Ford agreed to make a ‘goodwill’ contribution to the cost of a replacement engine, leaving her with a £2,700 bill.
Who is doing this job for a few hundred dollars? Tell me, because I’d rather pay that price than do it myself.
You know, when a spark plug or coil pack fails prematurely I get the car towed and then replace those parts and things are all good again. When a belt fails prematurely, well, it totaled my dad’s beater V70 because who’s going to put a new engine in a $3000 car?
Currently all the belts on my engine are wet with oil, but that’s because of a massive oil leak coming from somewhere on that side of the engine. It’s so bad that the wheel on that side has oil all over it 🙁
(Anyone know much about the VW/Skoda BTS 1.6?)
The consumer protection rules help somewhat in the EU – even after the factory warranty period. There is an ”expected working life”, and it is expected that during that period the engine should stay together, if you follow the official maintenance schedule. Sounds good, right? Yes, if you can prove that the service intervals were correct (easy?) and correct oil (and parts) were used. Always? Not so easy. Especially with the second/3rd owner. Did the indy garage use correct oil, how do you prove it? To make it even more fun, the wet belts really have to use very specific oils with very specific codes. Any 10w40 will not do, because the wrong additives supposedly eat the belt. Use it once, the belt should be replaced. There are stories that even dealership service depts have used wrong oil, especially in the early stage.
And the ”expected working life” thing? In practice, if the engine kabooms half way, you pay half. Reasonable? It depends – the manufacturer can specify the costs… sorry, the official fix is to replace the whole engine. We don’t sell parts. And for obvious reasons you probably don’t want to install a second hand one, which we would not agree to use anyway. So… with discounts, that would be 10k + labor and you pay half (for the engine that costs, what, 500? at the factory and should not yet have exploded).
Next, do an article about Ford’s wet belt driven oil pumps.
Yeah and the fact that they are behind the timing chains makes it even worse. The GM 3.0 duramax has the wet oil pump belt between the engine and transmission which seems convenient
When recalling the Takata airbag scandal, where engineers knew and warned management about the deaths long before they happened, I can imagine how these wet belts came to be:
The Ford CEO called an executive meeting, in a panic about looming fuel economy legislation. He instructed his executives:
“We need to find an 8% gain and we need it now. I want you to pull out all the stops and accelerate development. For every 1% you guys bring me, you’ll get an extra ten million in your bonus this year. The government bail out money, coupled with the windfall we made by cutting new hire worker wages in half, will easily cover the cost. If any of you motherfuckers fail to bring me at least 1%, you can expect a ten thousand dollar cut to your bonus. Of course, you’ll be able to claim the 10k back as an expense afterward.”
A highly motivated executive calls his engineering team lead:
“I need a one percent improvement in fuel economy by the end of this week. Don’t disappoint me, unless you want to be replaced with a fucking intern like what happened to Hank.”
A week later the Exec calls back:
“Well, what did you come up with?”
“Well sir, all we’ve got is this wet belt technology, which could give us our 1% but it’s showing serious deficiencies in our long term durabil..”
“Shut the fuck up! Will it get us through the warranty period?”
“Well, yes sir, in most cases, but there’s cause for seri…”
“It’s a yes or no question. Put the fucking thing into production.”
“Sir I really feel like this could hurt our reputation and affect our customer base long term..”
“Well done Hank. Fuck, I mean Larry. Thanks Larry. Hank was the asshole I fired last weak because he wouldn’t shut up about his killer exploding airbags. Anyways, great job. Tell the team you guys have a pizza party coming your way!”
Similar words rang out in other boardrooms infected with a corrupt and toxic corporate culture. Luckily Ford had already engineered the solution for them.
Many executives made a quick buck, and they all knew exactly what kind of cursed mess they were forcing on their customers.
Question… do we even need timing belts anymore? Your you not build an engine without them and use computer controlled mechanics? This avoiding the risk it a timing belt failure?
Not sure it matters much anymore with the use of electric motors.
They’ve been playing with the idea for the last 40 years or so, and I believe they’ve implemented the technology to a certain degree on some engines. An issue I can see is that electronics most certainly do fail. Timing chains are a better and more reliable solution.
Timing chains were a better solution for overhead valve engines where they ran around 2 sprockets (crankshaft and camshaft). Once they tried them on OHC engines and had to have tensioners, the system became significantly less reliable. The real solution is dry belts and non-interference engines so a timing belt failure doesn’t take out the engine.
Properly designed timing chain systems on OHC engines are maintenance free and significantly more reliable than any belted system, even when driving 4 cams. With modern chain systems, they have eliminated all the shortcomings of belted setups.
Do they still have tensioners and and plastic guides?
Probably, but it doesn’t really matter what they have because it’s a maintenance free system that lasts the life of the vehicle in most situations.
I know these are failure points on many poorly engineered German systems and so on, but these almost never fail on something like a Toyota.
Strange you mention Toyota, because the reason I sold my RAV4 V6 is the timing chain started rattling on startup, and because it was crammed in there you had to pull the engine to fix it. In my 1 year of ownership it also needed a brake booster and a AC compressor. Not really a shining example of Toyota quality (I bought it with 110k miles on it.) Meanwhile I’ve had several BMWs and none have had any timing chain issues.
I guess BMWs are probably more reliable than Toyotas. Thanks for enlightening me!
You really dodged a bullet getting rid of that troublesome unreliable 2GR. That thing was a ticking time bomb.
You know Toyota sells a rebadged BMW.
Yeah I’m pretty sure the Corolla is a rebadged 2 series
It comes to price.. actuators especially for higher RPM applications are expensive. Actuators do eventually fail.
Koenigsegg uses their system, but it is for a million $+ car.
They’ve been trying the tech since the early 80s, but lack of any widespread adoption keeps the component price higher.
VW 2.4 TDI that was used solely in Transporter T3 and T4 was gear driven. It’s pretty solid, but also tends to granade pretty spectacularry if abused. But with proper maintenance there’s quite few engines with close to million kilometers. Friend used to have one ex-police van with 700+tkm. Pretty robust things.
Gear driven cams on heavy diesel engines are the norm, partly because it takes a lot of torque to drive the cam in most diesel engines, and accurate timing is so critical. In my decades working on them, I haven’t witnessed a timing failure.
The wet timing belt is what stopped me from pulling the trigger on a new Buick Envista. I’ve also read that just changing it is very expensive. If anyone can allay my fears, I’m all ears.
«Teflon for added resistance». Don’t you mean resistance to resistance or something? I don’t think Teflon is known for its resistance adding properties first and foremost.
I will go on and read the article now,sorry.
Added resistance to oil damage.
Driving 4 Answers is a great YouTube channel. Watching his videos is a good use of a rainy afternoon.