She Runs! But Looks Like Cam Chain Issue

[JP Rodkey]

Last weekend I posted issues with my just acquired '98 that had "lost a coolant hose and overheated - shop advised replacing the engine." Although I finally got it to crank, it wouldn't start - until today.

A cold compression test showed between 90 and 110 psi on each cylinder (closed throttle because I was doing a quick check for compression). Installed new plugs and after a lot of cranking, the engine began to trot and finally started after about 18 months of sitting idle (68k miles on engine, no coolant installed). Lower end sounded very good with no knocks or unusual sound. But there is a definitely not-normal sound coming from the front of the engine and occasional popping into the intake manifold. Engine revs following throttle opening. There is no smoke or unusual odor coming from the exhaust. It will idle properly, except for the noise. If I shut it down and restart, it takes about 30 seconds of cranking until it trots, then will go ahead and run on it's own.

I will likely do a leakdown test, but it sure sounds like a timing issue on at least one bank (1-3). In view of the overheat history, I'm guessing that it may have affected the chain? It appears the RMS is performing like most - leaking. Here are my questions:

1. It isn't going to fix itself and whatever is making the noise is going to require removing the engine.

2. I am capable of doing all the work necessary to disassemble and reassemble the engine, but would have to farm out any machine work (yes, I understand Nikosil/Alusil and the limitations of working the block).

3. It doesn't act as if any valves are bent, just the timing affected. Anyone have success in such a situation by removing heads and/or replacing the timing components?

4. Already working on sourcing a replacement used engine, which seems the most economical, reliable, and practical solution at this point.

5. Should get Durametric software tomorrow and can then see what codes may be lurking.

Lots of folks have provided some excellent how-to's and photos, and I am willing to document the rest of the diagnosis and final solution if folks are interested.

Comments and opinions welcome..................

Edited July 31, 2008 by JP Rodkey

[rbizet]

Hi,

You should try taking a look at that site www.986fix.com

The whole engine rebuilding is very well documented in videos.

Good Luck !!!!

[JP Rodkey]

I spent a bunch of time on his site last night. Looked through most of the photo posts as well. Good stuff.

Right now, I'm leaning toward taking the engine out this weekend and starting the teardown to see what's up.

[JP Rodkey]

Update:

Likely root cause of problems was a water pump impeller that had separated from the shaft, likely caused by the worn bearing which caused the shaft to offset enough that the impeller began hitting the wall of the block port.

Leakdown shows roughly 90% leakage in two of the cyclinders tested - enough to warrant pulling the engine.

Durametric shows four codes, the important one being P0102 which is DTC 115 - hot film MAF sensor. Unless someone has a different opinion, the engine will be out within hours.

Edited August 2, 2008 by JP Rodkey