XJ XJ6 / XJR6 ( X300 ) 1995-1997

Got lower timing cover off but chain looks fine

Old 01-26-2019, 01:47 AM
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Default Got lower timing cover off but chain looks fine

So some folks may recall that I just purchased yet another X300 car, a 1995 XJ6 VdP that the previous owner claimed had a broken lower timing chain. In fact I bought the car with the engine partially disassembled. The previous owner had taken out the radiator, AC condenser, and most stuff off of the front of the motor in preparation for removing the lower timing cover. He had told me this was because the lower timing chain was broken. He said he confirmed this by spinning the engine over with the cam cover removed and said the cams did not move with the crank. So once I got the car back to my shop, I set about finishing the job of removing the lower timing cover. All that was left to do was the AC compressor bracket and the water pump. Once I got those off I discovered one of the lower timing cover bolts had broken off in the cover and I had to drill down through the shank of the bolt to get it freed up.

Once I got the timing cover off, I expected to find an obvious problem with the lower chain. So I was very surprised to find NOTHING unusual with the lower chain. This was yesterday afternoon and at that point I had to leave the shop. I did not get back there until today. I immediately put the crank damper back onto the front snout of the crank and proceeded to turn the crank bolt with a large breaker bar. I immediately discovered that it was necessary to replace the upper timing chain tensioner so the upper chain would properly mess with the intermediate gear, Once I did that everything spun over fine with the breaker bar.

I really do NOT understand why the previous owner would go to all of the work of disassembling the whole front of the motor after having convinced himself that the lower chain was somehow broke and then when I finally finish disassembling the engine, I do not find a single thing wrong. This all makes no sense to me at all.

Front of motor after removal of the water pump

After removing the lower timing cover, Can still see the remains of the broken bolt in the lower left edge of the block that I had to drill to free up the timing cover
The following 2 users liked this post by JensenHealey:
Don B (02-02-2019), SleekJag12 (02-01-2019)
Old 01-26-2019, 04:13 AM
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So now its onto check for bent valves?
Old 01-26-2019, 06:08 AM
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A compression test will give you that information

300 RPM min 110 to 117 PSI

You will probably need to recondition the rings for a decent result
Old 02-01-2019, 01:58 AM
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Glad to see the timing chain is not broken. Or anything else in there. That was quite a story the seller told, but most around here were not buying into it. Those timing chain systems are tough. We continue our record of zero broken timing chains reported, for now.

Maybe the seller thought the chain was broken because he took out the upper tensioner first, and then turned the crank by hand. As you found out, the upper chain won't engage the intermediate sprocket with the tensioner out. Hence the cams didn't move at all when he turned the crank. I'd bet prior to that, the engine had some kind of running problems (or non-running problems). As he started to troubleshoot and disassemble a few bits, he was led to the wrong conclusion when he tested for cam movement with the tensioner out.

There is hope for this engine if you are inclined to bring it back to life. Of course the cam timing must be reset correctly. It can be done. Good luck.
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