Timing Belt

[PorscheGals]

OK, my timing belt goes on an 87 944S. I take off the front covers, and thanks to all the prior posts I think (?) I can handle the belt replacement. Here's the question: How do I know if the valves are bent? Do I need to remove the head to be sure or is there a quick way to check? Thanks.

[gmaltz]

Is it routine maintenance or did you experience a sudden engine stoppage? If you did have a belt failure then you might have some bent valves.

Or you might have bent valves from a twin cam "Chain" failure, which is common around 90k if the tentioner was never maintaned. Take the cam cover and inspect the chain for any problems.

If you are doing just regular maintenance with a belt change, a compression check will let you know. But I would not spin the engine over if you suspect valve damage. You will just creat more problems like piston damage.

[fred cook]

Try pulling the spark plugs, use a flashlight and try to look into the combustion chambers. If that fails, replace the timing belt with everything set to the correct markers and SLOWLY turn the engine over by hand. If you meet any stiff resistance, then you probably have bent valves. If the engine turns over easily and you can see the valves opening and closing thru the spark plug holes, then you might be ok. The next step IF the engine rotates easily with the plugs out would be to do a compression check. Leave all the plugs out, block the throttle open and pull the fuel pump relay. Have an assistant crank the engine over while you watch the gauge and listen for expensive noises. Test each cylinder this way, recording the values off the gauge each time. If you have bent a valve, the compression in that cylinder will be much lower than the rest. For example you might read 170, 175, 175, 20. If all the cylinders read about the same (+- 10%) then the valve are probably ok.

Good Luck!

Fred Cook
'88 924S (previous life)