Problems with my 91

Recently bought my 91 and has what i though was a water pump bearing going bad. Thought no worries. Easy enough to fix. Now with the new water pump in... I'm finding the noise hasn't gone away. It's actually coming from the Main pulley just below that. Actual pulley shows no sign of wear or abnormal rubbing. This is inside. Engine runs great! No ruff idle, start, anything. Any thoughts? Sorry folks. Yes, new here and to the XJ. My 91 has the HO I6, 90k original miles on it. Any and all help is needed. Thanks

Tighten the belt more.

93gc40 said:

Tighten the belt more.

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I thought it was plenty tight already? Not really belt slipping sound. More inside just behind the pulley. But hey i'll give it a shot.

A good way, if you do not have a tensioner apparatus to check it. If you can twist your belt forward or back more than 90 deg. its too loose.

Yeah the belt is a little loose. haven't had a chance to get to it though. Did have a buddy listen to it. Said it sounds like a timing chain is stretched a bit and making noise. In all honesty i have no idea what the timing situation is in the HO I6?? Chain, belt, gears? Hydraulic tensioner?

It's a chain under that cover right behind the harmonic balancer.

I don't know the statistics, but the timing chain on our 4.0s will usually last a lot longer than 90k.

The "main pulley" is the harmonic balancer kastein refers to. This can look normal but requires a very careful inspection. The rubber ring often deteriorates and bulges out, rubbing against the timing chain cover causing a racket and eventually eating through the cover if not replaced. Again, I don't know the typical life span of the balancer (HB), but it is something to check. FWIW on my '85 2.5L, the HB and timing chain both failed at around 270k.

I believe the tensioner for the '91 4.0 chain is a simple snubbing block mounted on the side of the timing cover. A tubing "stethoscope" may help sort out the sounds coming from that area.

My timing chain is presently at 128k and doing fine - I'm probably jynxing it by saying that. I'm going to take a look at it when I do my RMS and oil pan gasket with my next oil change... hopefully... assuming I have the time. They recommend replacing the timing chain *before* it fails because depending on the engine design, Bad Things can happen when it breaks or slips a few teeth and the valves/pistons are no longer synchronized properly.