2 replies to this topic

[Coach]

Is it possible to do an accurate compression test on a 98 Contour with a broken timing belt without first replacing the timing belt? Car has a Zetec 2.0 with VCT.

Edited by Coach, 16 May 2012 - 12:56 AM.

[Terry Haines]

..I assume by your post you wish to establish if the pistons have kissed/bent the valves.Not easy without the belt in place.Best I'd advise is a leak down test.
With cam cover off the cams must be on the bases circle to the valve,so both valves are fully closed. The pistont must then be put at TDC...turn the cams and crank WITH CARE, you may have debris in a cylinder ,use a socket and wrench to position the cams and piston on each cylinder,do one cyl at a time.
Once the piston and cams are set you can put air pressure into the cyl and check the leak down time.Do all of this with care as too much pressure could 'kick' the piston down the cyl.
Your aim is to establish if the valves and piston hold pressure...if not then chances are a valve may have kissed the piston and will not give a gas tight seal...

[Coach]

Thanks for the response. Trying to help my out of state son. His timing belt broke last week. The guy at this small shop wants to do a valve job with the timing belt due to compression test values in the 90s. I've been going back and forth with him on the phone expressing my concerns that valve damage on a non-interference engine is not the norm. I'm not sure if any of the stuff in STB 98-9-8 would effect how he's doing his compression test. The car wasn't the best running at low speeds before the belt went. Not sure where the compression values were before belt broke. Just trying to help the kid from spending the extra $800 for valve job if not neccessary.