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Is your engine's Timing Belt pre-failure stage, do you know the symptoms?

5K views 13 replies 8 participants last post by  BiOhAzArD 
#1 ·
Having ownership and DIY experience with the car known with the longest and most finicky timing belt system ever put on an engine (Porsche 928s4) for the last 14 years, I have read hundreds of timing belt failure stories and how exactly they happened, which part was to blame, all the signs to watch for, it is kind of an art you could say, just like anything else. This would probably make a good thread to put in the knowledge base for DIY reference.

Coming armed with all that experience, all the below symptoms are definite signs that you should stop driving your car until the TB system has been inspected and re-done.
Pop enough clips with a flat head screw driver to open up the TB cover, use a very bright flashlight (at least 100 lumens) to see down in the system better. Then also get under the engine and look at the TB cover drain hole for leaking fluids or a hole full of particles.

For instance, if the belt is off of its center on the cam and/or you find significant amounts of black rubber dust under the cover , that is a sign that one tb system component mounting bolt or part is either bent or worn beyond service life, and it is very near failure.

Dust or shavings of other compositions under the belt cover, such as plastic or metal should also be a definate warning sign to park the car until the TB system can be fully inspected and re-done.

Green drops or fluid coming out of the belt cover= Water pump bearing is at near the end of its service life.

The belt will often start losing rubber teeth or parts of them as it ages, and cracks are all signs. If it loses more than one tooth in a row, the belt could slip especially if its loose and as a consequence the car will run poorly, and then eventually the further slippage will cause the valves will hit the piston tops = Grab your ankles $$$$. Definately not something to dick around with, park it until you can get that belt system re-done!

The belt looks very glossy, a sign that heat from a failing bearing is causing the belt to glaze, also usually accompanied with a crack or few in the belt.

A new metallic noise in the engine compartment while idling or revving the engine, should be traced down in quickly to see where its coming from. It could be a bearing on it's last leg (or ball)!

All these things are what I look for, and if they do happen, I will park the car until it can be verified and repaired. Mainly because re-doing the head is a PITA and I have enough of those already to deal with! I hope this saves you all from some headaches and wallet pain!

I've gotten pretty good at catching them in pre-failure stage, I am starting to have delusions that I may be a TB Jedi Knight :lightsaber:
Any other inputs on looking for symptoms will help everyone and are appreciated!
 
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#2 ·
A very useful post with some good pointers on how to prevent TB breakage/slippage. Thank you Hans.
One question, I had my TB and water pump changed last month, they also put a new alternator, belt and A/c belt too (iirc).
Is there any way to actually check to make sure that they did change the TB? (A new garage I have't used may times...)
I read somewhere you can check the date stamp on the belts. Is this right? Of the two belts I can easily see (haven't removed the TB cover yet) all I can see random numbers.

Thanks again for the pointers ;)
 
#3 ·
I would just pop open the inspection cover and take a look at the belt's condition, color, gloss level, signs of wear, staining, etc... Take a few pictures of it, the water pump and any other parts that were supposedly done in the job, in various positions after you have turned the starter on it and post them in here, I can give you some feedback. There may be a date code on the belt, but if its been sitting in a warehouse for a couple years, then it may not be a super accurate indicator.
 
#5 ·
Not sure if you intended to only talk about belt failure, but one of the more common failure points is the hydraulic tensioner itself. You need to check the tension and deflection of the belt, and to look for the mineral oil leaking from inside the small piston chamber. The oil is very thin and almost transparent, and even though it may feel glossy, it will be very very hard to identify visually on the bracket or the surfaces. For a brand new tensioner, a good indication is that the piston extends very fast when you pull the pin, less than half a second.

A scan is also essential if you have a CEL.

The best defense is to have the service history of that TB system. Quality parts go a long way also.
 
#6 ·
It could be a bearing on it's last leg (or ball)!


Face Nose Head Line art Mouth


I would like to add:
While the engine is running, look behind the covers and see if the belt is wobbling.
Slight wobble could indicate incorrect seating, or even a damaged pulley. <--- I have seen it happen and it was MY car ON the high way and I was "on the struggle" financially when I noticed it.
Saved my ass!!!!


And YES my goal is to scare all of you!
Now every body go and check yalls TBelts xD
 
#7 ·
Yep, those last two posts are very good advice, and one of them I forgot about, the old timing belt wobble test!

Excessive belt deflection or twist is an indicator that something has gone amiss in the system, usually either a tensioner, a bent pulley bolt or pulley bearing getting loose.

Any of those issues means the end is near and pray for mercy to the car Gods. lol And for the love of chicken wings, don't keep driving the car until its been repaired. :chillpill:
 
#8 ·
Great list of symptoms and cautions, but of course some have failed w/o warning. Make sure your water pump and idlers and tensioners were replaced the last time your belt was. I am told that a belt will erode on its outer edges, growing narrower with use, so if one knew the original exact width, one could perhaps determine whether a given belt was new or nearly so.
 
#10 ·
I am told that a belt will erode on its outer edges, growing narrower with use, so if one knew the original exact width, one could perhaps determine whether a given belt was new or nearly so.
I was actually shocked to see my Daughter's '05 3.0 timing belt once the covers came off. The belt was disintegrating at various places on the belt edge, there was no guessing that it was time to change. At 112K miles.
 
#9 ·
Hans, here are the pics .. TB, tensioner, water pump etc all done 4 weeks ago.
I think I should be ok because 2013 is written on the belt .. :homer: is that right? and does anyone know what the other numbers mean just for the anyhoo

[URL=http://s1070.photobucket.com/user/nibirugalaxy/media/22bae16c-da9c-40fe-a193-64de5e693304.jpg.html][/URL]

[URL=http://s1070.photobucket.com/user/nibirugalaxy/media/20140503_2004391.jpg.html][/URL]

[URL=http://s1070.photobucket.com/user/nibirugalaxy/media/20140503_2004021.jpg.html][/URL]

[URL=http://s1070.photobucket.com/user/nibirugalaxy/media/20140503_2002441.jpg.html][/URL]
 
#11 ·
Hans, here are the pics .. TB, tensioner, water pump etc all done 4 weeks ago.
I think I should be ok because 2013 is written on the belt .. :homer: is that right? and does anyone know what the other numbers mean just for the anyhoo
That pic looks off... I did my timing belt 2 months ago, and I have no markings from wear on ANY of the belts.

The power steering belt looks glazed, and the friction marks on the back of the timing belt look strange. It could be normal, but mine do not look like that. The continental branding/part numbers on the belt still show as when it was new.
 
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