Terrible squeal after a short drive

After taking a very pleasurable short drive in my '89 XJ40 it developed a loud squeal while pulling into the garage.

This had the sound of a slipping fan belt with some other odd metallic clicks thrown in. Curses. When starting the car it runs perfectly smooth and quiet for about 5 minutes or so then the the noise starts. It comes from the front of the engine at lower RPMs just off idle and disappears with increased throttle.

Checked that the two fan belts were properly tensioned, cleaned, and applied belt dressing. No help.

While the noise was occurring it seemed a few times my mechanical fan would all of a sudden greatly increase the airflow and the noise would simultaneously stop and then slowly return. So thinking that the fan clutch was at fault I removed the fan/clutch assembly but the noise and symptoms remained.

While the noise was occurring I put pressure on the water pump/alternator belt with a “J” roller (the tool you use gluing down formica) and the noise greatly increased. Doing the same thing on the A/C belt didn’t make a difference in the noise. So I listened to the alternator and water pump with my stethoscope but nothing sounded unusual.

  1. Because it not only had a squeal but also a metallic sound now and then I removed the cam cover and everything looked normal, nothing floating around and the upper timing chains were nice and tight.

  2. Since the noise increased with pressure on the water pump/alt belt I think I can rule out any internal engine problems. So I believe this would narrow it down to the water pump or alternator (both of which are fairly new), or the original harmonic dampener that has 160k on it. I have no idea what the symptoms of a failing harmonic dampener are or how I could troubleshoot it.

  3. I’m think the next thing I can do is to remove both belts and run the engine, but will the engine start without the alternator and would that create any electrical problems?

Some engines have harmonic dampers that are essentially two parts pressed together, with a rubber layer in between. If the damper/rubber/damper starts to slip, you will hear the noise you describe.
Get a paint stick and draw a straight line across the damper, and then run the engine. If the damper is slipping, your straight line will no longer be straight!


Thanks I’ll do that but what would account for the intermittent metal to metal sound ?

If the harmonic balancer proves to be ok after the paint mark test, take the drive belt off and try spinning the alternator and water pump by hand to see if you can detect any binding, play or grittiness, before you do that you could try spraying WD40 into the alternator bearing while the engine is idling to see if the noise stops or changes.

I think the engine would run without the alternator, but with that belt removed and no coolant flowing the engine would get hot really quickly and you would still have to determine/decide whether it was the pump or the alternator.

Casso …

Since the squeal increases with pressure applied to the water pump/alt belt but not when I apply the same pressure to the a/c belt wouldn’t that tend to eliminate the damper as a suspect?

I know this kind of mental troubleshooting is very iffy but because I’m dealing with a cold I haven’t felt like getting under the car and marking the damper with paint … maybe tomorrow.

Assuming the battery is up to snuff.

Would it be feasible, purely for test purposes, to use a shorter belt to run just the water pump?

Mr. Grooveman - check out this Web site - I believe you will find it enlightening:

Cannot this be done top-side?

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Mike …

Thanks for the info !

Actually I thought of using a shorter belt just to the alternator which would eliminate the water pump as the culprit. It seems to me that the bearings in the water pump are more prone to failure because it’s bolted to the fan/clutch assembly which isn’t balanced.

But then I wonder if the squeal goes away was it really caused by faulty water pump bearings or now less drag on a bad damper ?

Screenshot 2023-01-25 at 7.12.40 PM

Generally speaking, a bad balancer screams the loudest on cold start, as the alternator is pulling the highest load / the fan clutch is locked in.

It would be unusual to have the noise after the engine has warmed up, but not entirely unheard of. Your description of the noise going away at higher revs does point more to the balancer as well.

Paint test for sure…

Those were my thoughts too, from your description It definitely looks more like Alt or WP bearings and if they’re worn enough to screech with a metallic clicking I think you would easily detect which one it was by spinning each by hand.

Probably be fine, but I think if the bearings in either the Alt or WP are worn enough to screech, with the belt removed he should be able to detect which one it is simply by spinning it by hand.

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Gents …

Also what is strange is that when the squealing was going on I didn’t rear anything unusual with my stethoscope on the WP, Alt, and A/C compressor.

The thing that really bothers me is that if it’s an internal problem like a broken timing chain tensioner or whatever. But the symptoms (sound doesn’t start until engine starts to warm up and abruptly goes away with an increase in RPM) don’t seem to point in that direction.

Thanks so much for all the advice, it’s great to have this help!! Tomorrow I’ll do the damper check.

My money’s on the damper. Not a big deal to change, Joe has a great youtube video on doing it.
When mine went, I thought it was another component too, but the line test confirmed it was the damper.
Good luck!

Larry …

Your bet would be well placed. It appears that the damper is the culprit.

If I’m not mistaken the damper is a solid unit and there should be no movement between any of the parts; bolt head, two pulleys, and reluctor ring attached to the back. So a solid straight line painted from front to back should alway remain … straight. And any variation on that line means the unit is slipping.

So off with it’s head and off to be repaired (I’m assuming there aren’t any new ones around).

Larry … can you please tell me where can I find joe’s youtube video you mentioned.

Mike … thanks for the damper repair info. I just called and the gentleman in Salem Oregon will
rebuild the damper for $226 which includes shipping … sounds like a great deal to me !!

Joe’s excellent video (a 94) is here - I used it as a guide when I did mine. Breaking the bolt with an engine crank is the way to go, very simple.

The bolts Joe refers to for a puller which he thinks may be metric aren’t actually metric, the balancer casting is ancient and goes back to much earlier jags, so theyt are actually SAE.

All Joe’s tips regarding re-installation are right on. I found his method using the longer bolt to get started worked great.
Re-installing the balancer bolt and getting the correct torque on your own can be a challenge, I devised a method which jammed the balancer in place against the workshop floor. I’ll look around for the tool and post a pic later.

As he says, don’t forget to protect the rad, easy to bash it.

As far as the threads for the 2 holes in the balancer (for puller) go, I did try the M8 1.25 x 65mm in the video but I found they were really hard to thread and started to chew up the balancer threads …later, checking on another site, a poster with an X300 suggested those holes are SAE and tapped 5/16"-18.

Tool I made up to jam the balancer against the workshop floor so that the 150lb torque could be applied:

It would be great if you took pictures of the process. By the way, are you going to replace the crankshaft front oil seal?

I wonder if it is possible to renew the rubber of the damper without using services of a specialized damper shop. :thinking:

Hello Otto …

I’ll certainly take pictures along the way and post them.

I haven’t thought of the front seal but with 160K miles and it’s not too difficult to do with the engine still in the car I think that’s great idea. I’ll have to research the procedure. With my car layed up for a week or two waiting for the damper to be rebuilt I’ll have plenty of time.

That is great.

The front seal part number is EAC7954. The procedure is illustrated in the Haynes manual.

I wonder if it is possible to find a suitable new or ”universal” damper from some other car brand. :thinking: