This past week my 98 XJR produced a loud noise on start-up. I immediately switched the engine off when I first heard it (2 or 3 seconds). When I tried again the noise was gone and everything sounded fine. I thought perhaps the starter had remained engaged, but a couple of days later, it did it while at idle, about 10 seconds after start-up, so I assume it is not the starter. It happened once again yesterday on start-up, then gone on re-start. I am wondering of it may be a belt tensioner or idler pulley. That may be wishful thinking as it is quite loud and ominous sounding, like something trying to seize up. On all three occasions it disappeared on the next start. It is hard to describe, but it is like a medium pitched whine with a bit of grind to it and is quite loud inside the cabin. If anyone has any ideas, I would appreciate hearing.

 

Have you replaced your secondary timing chain tensioners? This may not be your sound, but a 'grind' at start up is a common reference to the sound that is heard as the old, plastic tensioners are about to give up the ghost.

Probably best to open the hood and have someone else start it up while you try to locate the are from which the sound is generated - if it's near the front of either valve cover, the tensioner is a good bet.

 

I have replaced all 4 chains, tensioners & guides.
This sound is very loud. Now that I have heard it five or six times for 3 or 4 second intervals, it seems to be a grating noise, perhaps a bearing about to blow up. I am now suspicious of the air conditioning compressor. It has been hard to pinpoint, as it disappears as quickly as it appears. I am sure it will only get worse, which will likely help identify it. I will take your advise and have someone else start the motor. It seems to happen only at start-up, no trouble after that... so far. I am not sure if I can DIY the compressor or not, but would like to, if it is the culprit. No experience with A/C though.

 

definitely worth looking/listening to the idler pulley, they go quite often, then possibly the tensioner pulley. Of course, this coming from the guy who thought it was one, then the other, and turned out to be the power steering pump wailing from the lack of fluid due to a leak on the system. Of course, mine was very intermittent at first...just at the start of the engine cranking, but progressively, it was all of the time.

 

Thanks. I'll try the stethoscope on the idlers, (if I can, and carefully). But you gave me another good idea. I have not checked the power steering fluid level yet. I would be pleased if it was just an idler.

 

I have pretty much confirmed that I have an A/C compressor that is complaining loudly on start-up.

With a stethoscope I was able to hear the grinding by placing the probe just behind the pulley on the compressor. The belt idlers seemed fine.

Can anyone advise on whether it is possible to change the clutch only and avoid disconnecting the lines and purging the A/C refrigerant? Changing the compressor out seems fairly straight forward, but dealing with the refrigerant... not so simple for a DIY. I would still prefer to repair this myself if at all feasible, so any instruction from someone who has done this would be greatly appreciated. Every time I fix something on this car... it is a first time. I spend more time figuring out how to do it. I would need sage advice this time I think, rather than charging in with wrenches.

 

There are lots of AC help sites on the web. On a previous car I had an AC problem, bought a complete set of gauges, vacuum pump, etc. from Harbor Freight for about $125. Fixed the problem and then sold the stuff on ebay for just about what I paid for it.

Tight Wad Tom

 

I will do some research, but if anyone knows of a good writeup, please let me know. I saw an excellent one for an XJS, but the pump is much easier to access, allowing for clutch removal without disconnecting any refrigerant lines. On an XJR the pump is tucked away. It may be easier to replace the entire unit, but I would need some schooling on purging and re-charging, provided I can get the required tools. A/C seems to work fine. If it seems too daunting, I may have to take it in, but that would be no fun.

 

Upon closer inspection, I have discovered that rubber section in the outer hub on the clutch has deteriorated, allowing it to contact the inside wall of the pulley. That is what makes all the racket. Perhaps I can replace that component for now and avoid opening the system up. Born Again Air in Texas handle the parts I believe. Just hoping I can get it apart without having to remove the compressor. If not... might as well replace the whole thing.

If anyone has done this, I would appreciate hearing about it.

Best Regards

 

I had the same issue with a Ford product a few years back - a Mustang. In that case there was room to remove/replace just the clutch assy... don't know about the Jag.

Rock Auto shows a replacement AC compressor clutch assy for a 98 XJ8 for $145. DENSO Part # 4730308 - Compressor Clutch #MCA7300AE

 

Thanks Quad,
I had a look and it seems somewhat feasible with the compressor in the car, but I may have to take the sway bar off. Perhaps the radiator too if I need extra room for a puller. Will get the parts and go from there.

Wayne

 

Hmm, a bit painful, but still beats opening the sealed system, IMO.

 

Has anybody confirmed that this sound is the a/c compressor? For like a year now upon startup in the morning I get one loud but short grind sound. I've had my whole tensioner setup replaced awhile ago so I don't think that's it.

Thanks.