Timing belt failure... need some advise

[Franko6]

Pedro, thank you for the referral. I always appreciate people recommending my service.

The teeth being stripped off the belt, of course, is never a good thing. Usually it is age before mileage that causes the issue the further south or from our Mason/Dixon line the worse it gets.

but just because you have impact marks on the Pistons is not the end of the world. I call them “witness marks“ and it matters more what happened to the lifters.

We have received cylinder heads that had timing belt slips were all of the lifters are 100% good, and the camis in perfect shape. The cylinder head should never have come off.

The best advice I can give is to partially disassemble the cylinder head. Of course the timing belt must be removed, but we start by dropping the timing belt off for the cam sprocket, removing the cam caps and vacuum pump and even with the sprocket still attached, you can remove the cam and examine the lifters.

Once the cam is out of the way, any damage to lifter that is deeply bent downward is an engine speed strike, and the head must be removed. Also, any lifter that is bulged up as a starter speed hit. Either way, damage is either been done to the head of the valve or the stem of the valve. To return the engine to service without removing it bad valves is going to end up catastrophe, particularly when the exhaust valve snaps off, ruins your cylinder head, piston, rod and maybe even destroys the cylinder bore.

however, there is another strike which can be overlooked. I Collett a “incidental hit“. Remove each left her in order, and with a magnifying glass examine to see if the lifter has been fractured. A light fracture will not damage the valve, but if left in service, the lift her will work back-and-forth until the top of the lifter falls off, slides back in the lifter bore and the valve will cause a lot of distraction, definitely jump the belt and you’ll have a cylinder head now, that has to be removed.

Rather than completely removing the cylinder head, only to find out there is minimal damage; cam and lifters, you can save yourself a lot of trouble and time. But as bluntly as I can put it, if I have to remove the cam to see what is wrong with the lifters, so also, do you.

The point is, the lifters are the weak link in the chain and will damage whenever valve and piston contact is made. The very light strike may ruin the lifters, but we have seen the valves remain true. A badly damaged lifter equals a badly damaged valve.

I will be away from the business until next Thursday, February 3, if you need any additional support.

 

[sptsailing]

You will need to pull the head to see if it can be repaired.

 

[Franko6]

• Here we go again…. Check cam and lifters FIRST. We have had dozens of cylinder heads sent that had no bent valves. No lifter damage, then the question of the damaged valves is age and miles.

 

[bstrozr1]

Just wanted to follow up... we ran a compression test today before we did anything but get it back in time and ran between 395 and 415 across the board. My buddy is a Ford diesel mechanic and his logic makes sense.... it makes even compression across the board... why pull the head.... what are your thoughts? I have read a tdi should run around 500 psi... my motor has 270k on the odometer

 

[bstrozr1]

Pedro, thank you for the referral. I always appreciate people recommending my service.

The teeth being stripped off the belt, of course, is never a good thing. Usually it is age before mileage that causes the issue the further south or from our Mason/Dixon line the worse it gets.

but just because you have impact marks on the Pistons is not the end of the world. I call them “witness marks“ and it matters more what happened to the lifters.

We have received cylinder heads that had timing belt slips were all of the lifters are 100% good, and the camis in perfect shape. The cylinder head should never have come off.

The best advice I can give is to partially disassemble the cylinder head. Of course the timing belt must be removed, but we start by dropping the timing belt off for the cam sprocket, removing the cam caps and vacuum pump and even with the sprocket still attached, you can remove the cam and examine the lifters.

Once the cam is out of the way, any damage to lifter that is deeply bent downward is an engine speed strike, and the head must be removed. Also, any lifter that is bulged up as a starter speed hit. Either way, damage is either been done to the head of the valve or the stem of the valve. To return the engine to service without removing it bad valves is going to end up catastrophe, particularly when the exhaust valve snaps off, ruins your cylinder head, piston, rod and maybe even destroys the cylinder bore.

however, there is another strike which can be overlooked. I Collett a “incidental hit“. Remove each left her in order, and with a magnifying glass examine to see if the lifter has been fractured. A light fracture will not damage the valve, but if left in service, the lift her will work back-and-forth until the top of the lifter falls off, slides back in the lifter bore and the valve will cause a lot of distraction, definitely jump the belt and you’ll have a cylinder head now, that has to be removed.

Rather than completely removing the cylinder head, only to find out there is minimal damage; cam and lifters, you can save yourself a lot of trouble and time. But as bluntly as I can put it, if I have to remove the cam to see what is wrong with the lifters, so also, do you.

The point is, the lifters are the weak link in the chain and will damage whenever valve and piston contact is made. The very light strike may ruin the lifters, but we have seen the valves remain true. A badly damaged lifter equals a badly damaged valve.

I will be away from the business until next Thursday, February 3, if you need any additional support.

Thanks franko6. I don't know why I just saw this. Wouldn't have posted my last post.

 

[Windex]

At the very least, take the valve cover off and look for fine spider cracks on the tops of the lifters. Also, re-read all of the above posts telling you that a valve has a good chance of fracturing, falling off and trashing the entire engine.

Why ask the question here if youre going to ignore the answers?

 

[bstrozr1]

I'm just trying to make an informed decision. I'm not ignoring anyone. I have a friend that is telling me one thing and the internet is telling me another. Just trying to compile all the answers. We are gonna tear it down and see what all has to be done.

 

[Mozambiquer]

Just wanted to follow up... we ran a compression test today before we did anything but get it back in time and ran between 395 and 415 across the board. My buddy is a Ford diesel mechanic and his logic makes sense.... it makes even compression across the board... why pull the head.... what are your thoughts? I have read a tdi should run around 500 psi... my motor has 270k on the odometer

The compression being even isn't an indicator of the valves not being bent, it's just merely telling you that they're not bent in a way that they don't seal anymore. They could be accordioned and still seal correctly, but they're still bent.
Franko6 has a good way to tell, though from what you mentioned in the beginning, you've already changed the cam after that? Is that correct? Personally, I would probably pull it, as I've seen too many broken valves take engines out.

 

[bstrozr1]

The compression being even isn't an indicator of the valves not being bent, it's just merely telling you that they're not bent in a way that they don't seal anymore. They could be accordioned and still seal correctly, but they're still bent.
Franko6 has a good way to tell, though from what you mentioned in the beginning, you've already changed the cam after that? Is that correct? Personally, I would probably pull it, as I've seen too many broken valves take engines out.

I haven't done anything other than retime it. I've been trying to make sense of what everyone here is telling me and what my buddy is telling me. At this point I plan to pull everything down and follow Franko6's advise. If we see anything that looks bad we will pull it down further. I have ordered a new cam, followers, and lifters. From there we will check for cracks. Im torn because I don't want to destroy my engine but what my mechanic buddy is telling me isn't wrong either. Hopefully if anything is wrong it's obvious and we correct it while it's torn down.

 

[turbocharged798]

Ok TDIs are unique because the piston hits the valve straight on, most engines the piston at one form or another hits the valve on an angle and bends it thus causing no compression. Because TDIs hit it right on the valve will still seal but the stem has squished and is now ready to break off. A few miles down the road and the broken valve bounce around in the engine and ruin the entire engine. What Franko6 is saying is correct, you need to pull the cam and look for damaged lifters. A cracked lifter means that the valve was hit by the piston and is now damaged. IF you want to roll the dice and run with it that's on you but there is a good chance you will grenade the engine.

Your friend would be correct on 99% of engines out there, however it does not hold true for TDIs.

 

[pedroYUL]

Fire your friend

 

[bstrozr1]

Ok TDIs are unique because the piston hits the valve straight on, most engines the piston at one form or another hits the valve on an angle and bends it thus causing no compression. Because TDIs hit it right on the valve will still seal but the stem has squished and is now ready to break off. A few miles down the road and the broken valve bounce around in the engine and ruin the entire engine. What Franko6 is saying is correct, you need to pull the cam and look for damaged lifters. A cracked lifter means that the valve was hit by the piston and is now damaged. IF you want to roll the dice and run with it that's on you but there is a good chance you will grenade the engine.

Your friend would be correct on 99% of engines out there, however it does not hold true for TDIs.

Thanks. He's a ford diesel tech. Not a vw guy. We know they are unique motors but they work. We are gonna check the lifters. I don't want to get it torn down and back together only to pull the engine so I am leery of skimping on it. I have a machine shop already to go through the valves if we think we need it. I still think I want to pull the head anyway.

Thanks for the input!

 

[oilhammer]

Most all diesels (and many gassers... including all the SOHC VAG engines) have the valves running straight up and down directly in line with the pistons. So the valve head does not "bend" to one side, as you'd see in a hemi or pent-roof type valve arrangement. When that happens, the valve won't allow ANY compression. Those are easy to check. Pretty obvious.

With the type like we are discussing here, the "bend" is far less obvious. You really cannot tell unless the valve is removed from the head. In some cases, you know as soon as the spring and keeper is removed, because the valve will not slide out of the guide. Because the STEM gets "scrunched" up. It won't be so bad that the spring cannot close it, nor be so bad that the cam/lifter cannot open it. Therefore, you'll have compression, and the engine will start and run just fine. But that stem binding in the guide will tear itself to death in short order.

We (TDI club, collectively, as well as anyone familiar with VAG engines), have seen this exact same scenario play out many, many times. Timing is compromised, engine gets fixed on the outside, it starts and runs, and several hundred miles later a valve breaks off and literally destroys the engine (and I do mean, destroy, as in, it may not even be fixable).

 

[Mozambiquer]

I've seen a lot of diesel technicians that can't figure out a TDI to save their lives. They're not wrong in their diagnostic procedures if they're working on a power stroke or Cummins, but a TDI isn't the same. I've also laughed as they talk about how hard they are to work on... I'll take a TDI any day over a 6.0 or 6.4 PSD.
If they can get past the preset mindset, they can do great at it. I work on both, as well as heavy duty diesels.

 

[oilhammer]

I've had some horror stories, too.... and I just don't understand what is so difficult. They are really pretty simple overall.

 

[Mongler98]

I've seen a lot of diesel technicians that can't figure out a TDI to save their lives. They're not wrong in their diagnostic procedures if they're working on a power stroke or Cummins, but a TDI isn't the same. I've also laughed as they talk about how hard they are to work on... I'll take a TDI any day over a 6.0 or 6.4 PSD.
If they can get past the preset mindset, they can do great at it. I work on both, as well as heavy duty diesels.

Yep sure is hard work chasing 14 to 20 quarts of engine oil vs 5 for a tdi!

 

[Mozambiquer]

I've had some horror stories, too.... and I just don't understand what is so difficult. They are really pretty simple overall.

Probably about like when I first worked on a HEUI. I could fix a VW, but that was this system??? I know how to now, but it was different.

 

[oilhammer]

You should have seen me trying to explain low pressure EGR to the guys at the ASE test meeting. Now it is becoming commonplace.

 

[Franko6]

"Fire your friend"... You know the problem with a 'friend' helping? You can't hold his feet to the fire when something goes wrong. I've seen it. "Yeah, he screwed up my engine, but he's a friend..." There is some truth in that, if he doesn't know what he's doing, he's not really being a friend. It's like a 'friend' that gives you a bad hair cut, but doesn't charge you for it. You don't have much room to complain.

The information I gave you is exactly right. I am not your 'friend'. I do this business as a livelihood, just like Oilhammer and Mozambiquer an I am not positive, but there are probably some of the others. These guys get paid to do it right.

The compression rate, it is low, assuming you have a tester that is good. Once again, if it's a cheapo Harbor Freight, the first thing we do with the insert is replace the Schrader valve. They are very often no good. The second thing is do not overtighten that brass fitting, as it 1)doesn't need to be that tight and 2) if you overtighten it, you ruin the insert and might even get it stuck in the hole. A good nudge is all it takes. 10 ft lbs. 3)Be sure to defeat any fueling, like remove the wire from the top of the fuel shutoff valve, or the first stroke, the fuel will fire through the gauge and ruin it.

Then, with the gauge installed on the test insert, me being a lone wolf in the shop, I set the gauge where I can see it under the hood, all other glow plugs are removed and the battery is fully charged. Run the starter until the gauge stops rising. It is not 5 strokes or 10 strokes. It's the highest reading you can get. The one thing about the Harbor Freight setup, I can't promise the gauge is accurate, but it probably is.

395psi is right at the bottom of the allowed reading. There should not be more than a 10% variation. If it was 450, that would be fine. My own engine, last check, it was 500psi across the board.

Good luck.