Cam Belt

[swift]

The cam belt broke on my 1994 S4 can I just have the belt replaced or do I have other problems, i.e. bent valves and cyl. head work. The belt had 15000 miles on it over 7 years, it is in one peice and still on the car but 5 theeth are missing. Thanks

[chris]

Did the engine sieze or cut out or did you just notice the missing teeth? ? ? I'm afraid its a case of suck it and see. You could fit a cam belt and do a compression check and see how the engine turns over and runs. Or you could take the head off and see what the damage there is if any. If you remove the head and there's nothing wrong then its alot of expense for nothing. If you replace the cam belt but it wont turn by hand or there's no compression or it simply doesn't run right then your back to square one. It really depends on how much money you want to throw at it? Stripping it is the sensible safe option. Although if you have only bent one valve you may as well replace them all while the head is off so i personally wouldn't worry to much about a little extra damage. Unfortunately it really is down to your own opinion and how deep the wallet is? Have you consulted any garages as yet? You should get a varied opinion on this subject depending on how mechanical minded people are. sorry not to be able to help more.

[Paul C]

If it were me i'd get it looked at, worse case is you will end up with a new head gasket and

a bit of labour, worse case they will find damage that could quite possibly been made much

worse by re-belting and running the engine again.

Regardless of miles i have the belt changed every two years as per the service interval,

this means that the most miles i've ever done on a belt is about 6000 before changing it.

Sometimes i DO think it seems like overkill and expense though...

Hope your's turns out not too bad.

[CNH]

I suppose since you asked such a question that you are not a DIY type of guy and require the services of a shop for repairs.

If the motor was turning (bottom)and the cams were not you are pretty much hosed and your will do a top rebuild. If you are or have a friend who is handy to replace the belt and run a comp check on it. Maybe you will be lucky.

Hope you have money as any type of major work will test your finances.

[Paul93Lotus]

I suppose since you asked such a question that you are not a DIY type of guy and require the services of a shop for repairs.

If the motor was turning (bottom)and the cams were not you are pretty much hosed and your will do a top rebuild. If you are or have a friend who is handy to replace the belt and run a comp check on it. Maybe you will be lucky.

Hope you have money as any type of major work will test your finances.

Possibly a boroscope through the plug holes could shed some answers...i.e see visible scarring on the piston tops from valve collision? You should see some evidence of interference if any with a scope.

[Paul C]

Possibly a boroscope through the plug holes could shed some answers...i.e see visible scarring on the piston tops from valve collision? You should see some evidence of interference if any with a scope.

Aha!

But what if the belt had snapped on this car in the past?

Say the valves are bent/broken (which is likely, sadly).

The head comes off and gets reconned and/or new valves fitted.

When it's all put back together and running 100% fine then you

will still always see the evidence (i'm guessing) of the scarring on

top of the pistons, does not mean it came from this occasion...

As the car is long due a cambelt service then the tappets probably need

doing too, and if the cams are coming out then you might as well go the

whole hog and take a look i figure.

In seven years the saving from the 3 'C' services that should have been done

will i guess (figure

[DanR]

You could take the covers off the cam carriers and check the valve movements and clearances. Make sure the front pulley is 90 degrees off TDC first so the pistons are halfway down.

Not confident some valves aren't bent though.

[CNH]

Just to ask is the 5 teeth missing on the belt all in one place on the belt?

He mentioned that the belt is still on the car

Did anyone bother to check if the cams are in sync with the crank timing and if they are off by how much?

Did he turn the engine by hand? Surely he did not run the car after he noticed the belt.

What made him check the belt if he had gone so long without checking it before? As in did the engine stop running or running rough after the 5 teeth were sheared off?

[Esprit Aviation]

Calvin,

You present a very good point. All else is academic until your questions are answered. 5 contiguous missing teeth on the belt still may not cause a timing problem and hopefully all is well!! I say rebelt it (VERY CAREFULLY) and see. Especially, if the timing is either right on or off by a few teeth.

Paul,

I forgot one thing. If the valves contacted the pistons @some point in the vehicles past, and was run since then, the marks from piston/valve contact would likely be covered w/ a bit of carbon. If the valves just made contact and presumably bent, then there would be a shiny gouge or other mark on the piston crown.

Lee

Edited December 14, 2006 by Esprit Aviation

[CNH]

Is there anyone nearby this person to give him some help?

If the cam belt damaged but is still on the engine a quick check will end the speculation just by turning the engine by hand and seeing if the timing marks line up. It will have to someone familiar with the process. If he had run the engine as it is now I would think it would not cause further damage than it has now. I have seen rebuilt engines damaged by turn the crank hard by hand if not done by proper feel when the timing was off but in this case I would think any damage would have already occured.

If the crank timing is right on or tooth or two off the engine still might still be undamaged. If the crank timing is fine a belt change and a compression check is a lot less than taking apart top of the engine.

[swift]

Well, A bit of history as it was told to me. The car was in my storage and it was being moved to get one of the other cars out, so it was running when all this took place.

The reason I asked the question was to help me make a decision. If this is a non interferance engine I can have the belt changed and have it mobile again or if it is not I will get rid of it as is. I do not want to tie my work space or my help up with another project of a top end rebuild.

But no one seams to know for sure so this must be the first S4 to have a belt broken. Sad I did enjoy the car the times I drove it and it has a total of 18,000 miles on it but other things to do so it will go as is.

Thanks again for the help guys. Lloyd

[Paul93Lotus]

Well, A bit of history as it was told to me. The car was in my storage and it was being moved to get one of the other cars out, so it was running when all this took place.

The reason I asked the question was to help me make a decision. If this is a non interferance engine I can have the belt changed and have it mobile again or if it is not I will get rid of it as is. I do not want to tie my work space or my help up with another project of a top end rebuild.

But no one seams to know for sure so this must be the first S4 to have a belt broken. Sad I did enjoy the car the times I drove it and it has a total of 18,000 miles on it but other things to do so it will go as is.

Thanks again for the help guys. Lloyd

Definitely an interference engine. So I guess you're getting rid of it. We are just trying to help you figure out if damage was caused...because it is possible that it may have escaped bending some valves.

Pretty silly to sell a car "as-is" without first determining if it was indeed damaged though. But hey, if you want to take a huge $$$ loss for no reason, to each his own. People don't like buying surprises.

[CNH]

Well, A bit of history as it was told to me. The car was in my storage and it was being moved to get one of the other cars out, so it was running when all this took place.

The reason I asked the question was to help me make a decision. If this is a non interferance engine I can have the belt changed and have it mobile again or if it is not I will get rid of it as is. I do not want to tie my work space or my help up with another project of a top end rebuild.

But no one seams to know for sure so this must be the first S4 to have a belt broken. Sad I did enjoy the car the times I drove it and it has a total of 18,000 miles on it but other things to do so it will go as is.

Thanks again for the help guys. Lloyd

Oh we all know what happens when the cam belt breaks. It bends your valves and nicks the pistons. As stated most of us know for a fact that it is an interference engine and if the top 1/2 stops with the bottom in motion it will be a head off repair. There is no question in my mind about that. Before your reply about the history there was some hope that maybe it just skipped a tooth or so and that would be the saving grace. It now appears that some of the valves have been bent.

Time to sell it for what you can get then for it. What country is the car located in? Only reason I ask is that some people do have a new turbo chargecooled engine sitting in a crate. Not that they would sell it but maybe they might buy the car if it was cheap enough.