Intermittent "squealing" sound?

[topt]

Triton 2.5L Diesel, manual, 4 years old. Last service end October and since then I occasionally get a squealing/screeching sound which I am guessing is a belt slipping. Sometimes I get this 2/3 times in a 50km journey and sometimes not at all. First few times it happened I thought it was when accelerating hard from 2nd to third but other times seem to have been very random. Other than the noise does not seem to have any other effect.

Can someone suggest what they think it may be so I can try and give some guidance to a garage?

[Slip]

Fan belt?

[Gsxrnz]

Yep, belts. Probably more noticeable when it's raining or on a cold start after the (relatively) cooler nights that we're now experiencing.

Just go to a dealer and get them replaced at your next service.

Edit: But at the same time, make sure it's not an issue with the bearings in your alternator, water pump, or a/c. They should have a stethoscope to be able to isolate noise from a worn bearing that may be making the noise. However, 95% chance it's just the belts.

Edited December 15, 2015 by Gsxrnz

[IMHO]

Yep, belts. Probably more noticeable when it's raining or on a cold start after the (relatively) cooler nights that we're now experiencing.

Just go to a dealer and get them replaced at your next service.

Edit: But at the same time, make sure it's not an issue with the bearings in your alternator, water pump, or a/c. They should have a stethoscope to be able to isolate noise from a worn bearing that may be making the noise. However, 95% chance it's just the belts.

Good point on the bearings - I once lost an engine in a 6 month old car due to bearings in a serpentine belt tensioner failing. Since then, any squeaking sounds from under to hood get immediate attention from me

[MESmith]

Have you seen the wife recently?

[pgrahmm]

A failing alternator diode pack can "sing" when more charging is needed they can sometimes do this....

Try and tie the RPMs/temp/conditions in with occurance....As it is colder at night now moisture can form on the belts and pulleys but should stop after warming up....Also a belt tensioner might be failing/bouncing under certain engine speed demands/changes.....

Are ya missing a cat ?????

[topt]

Have you seen the wife recently?

A failing alternator diode pack can "sing" when more charging is needed they can sometimes do this....

Try and tie the RPMs/temp/conditions in with occurance....As it is colder at night now moisture can form on the belts and pulleys but should stop after warming up....Also a belt tensioner might be failing/bouncing under certain engine speed demands/changes.....

Are ya missing a cat ?????

Neither fortunately

phraham Not sure how successful I would be trying to explain that - also never happens first thing but thanks.

[topt]

Yep, belts. Probably more noticeable when it's raining or on a cold start after the (relatively) cooler nights that we're now experiencing.

Just go to a dealer and get them replaced at your next service.

Edit: But at the same time, make sure it's not an issue with the bearings in your alternator, water pump, or a/c. They should have a stethoscope to be able to isolate noise from a worn bearing that may be making the noise. However, 95% chance it's just the belts.

Good point on the bearings - I once lost an engine in a 6 month old car due to bearings in a serpentine belt tensioner failing. Since then, any squeaking sounds from under to hood get immediate attention from me

That is a bit worrying - again the issue is so intermittent it is unlikely the garage could replicate it. I will pay them a visit and see if I can get them to understand enough to check items other than the fan belt. Thanks.

[VocalNeal]

It will be the A/C belt as that carries the biggest load so that is where the squealing is coming from. It either needs re-tightening or replacing.

Short term you may use some belt dressing spray if you know which one it is but that is only a stop gap. Once they start to go....

This will fix you up. http://www.westernfilters.net.au/mitsubishi-triton-ml-mn-2-5-ltr-from-2009-2014-belt-pulley-kit-wbpk72n/

Who knows Mitsubishi Thailand may have the same kit?

Edited December 15, 2015 by VocalNeal

[regedit]

I had new belts fitted and the intermittent squealing started. Had them tightened but still squeals every so often, so I'm starting to think this might not be the belts.

[stevenl]

I had new belts fitted and the intermittent squealing started. Had them tightened but still squeals every so often, so I'm starting to think this might not be the belts.

I really don't understand this. You had new belts fitted and the sound started, but you think it is not the belts?

[Pomthai]

To determine if it is belt or alternator related, start the car, turn the AC off or set the thermostat to the highest temperature so the compressor isn't running. Switch on all the electrical loads you can such as rear window demist, AC fan full, lights on full beam plus fog lights and all the interior lighting. Then rev the engine if it squeals switch off the electrical load and rev again. It probably won't squeal. If this is the case repeat a couple of times until you can see a relationship between electrical load and squealing sound - if the above seems the case, then re-tighten or replace the alternator belt.

If doing the above you can't recreate the problem, try switching on the AC with thermostat the opposite direction (max cool) and see if that generates a squealing sound. AC compressors can get tight as they age or as the bearing or magnetic clutch begins to fail resulting in belt slippage (squealing sound). Again if you can recreate the squealing by cycling the AC on or off, combined with a few revs then it might just be loose belt or need replacing. If the belts tight and / or doesn't need replacing - have a dealer look at the AC compressor.

Either way, one of the above methods should allow you to determine if it is a belt and which one is causing the problems. If you can't replicate the fault by doing the above, I would guess its a belt tensioner bearing galling and seizing intermittently. Probably a dealer job - at least to get the parts.

Edit-: Just re-read the OP - the service in October? Did they top up the AC? If so it might have been over charged and in hot weather or after a long run and re-starting in the hot, the high pressure side my be too high increasing load on the compressor more than it should, thus belt slipping - intermittently and perhaps not easy to replicate. Solution is to have them check the AC refrigerant gas pressures and release some gas if overcharged.

Edited December 16, 2015 by Pomthai

[topt]

To determine if it is belt or alternator related, start the car, turn the AC off or set the thermostat to the highest temperature so the compressor isn't running. Switch on all the electrical loads you can such as rear window demist, AC fan full, lights on full beam plus fog lights and all the interior lighting. Then rev the engine if it squeals switch off the electrical load and rev again. It probably won't squeal. If this is the case repeat a couple of times until you can see a relationship between electrical load and squealing sound - if the above seems the case, then re-tighten or replace the alternator belt.

If doing the above you can't recreate the problem, try switching on the AC with thermostat the opposite direction (max cool) and see if that generates a squealing sound. AC compressors can get tight as they age or as the bearing or magnetic clutch begins to fail resulting in belt slippage (squealing sound). Again if you can recreate the squealing by cycling the AC on or off, combined with a few revs then it might just be loose belt or need replacing. If the belts tight and / or doesn't need replacing - have a dealer look at the AC compressor.

Either way, one of the above methods should allow you to determine if it is a belt and which one is causing the problems. If you can't replicate the fault by doing the above, I would guess its a belt tensioner bearing galling and seizing intermittently. Probably a dealer job - at least to get the parts.

Edit-: Just re-read the OP - the service in October? Did they top up the AC? If so it might have been over charged and in hot weather or after a long run and re-starting in the hot, the high pressure side my be too high increasing load on the compressor more than it should, thus belt slipping - intermittently and perhaps not easy to replicate. Solution is to have them check the AC refrigerant gas pressures and release some gas if overcharged.

Thanks for the detailed reply. Will try some of your suggestions tomorrow and then go see the garage.

[Jitar]

topt, the AC belt caused the same symptoms on my PJS. Dealer needed a couple of tries to get the tension right after replacing the belt. You can test by turning AC on and off at +3000 rpm.

[topt]

Tried several of the ideas mentioned above but could not get it to replicate.

Took it to the dealer and explained to one of the service ladies who spoke some English but it was clear she did not really understand. She got a mechanic out who was looking at the tyres........

Then I think my explanation got through and after popping the hood he had a quick look and said something in Thai - lady said it was the timing belt.....

Mechanic goes away and comes back with spanner and socket wrench and a tub of gook. A few turns and a final pull on the spanner and then spreads some gook on something down the front just back of the rad.

Job done? Did not have any noise yesterday on a drive but we will see over the next week or so.

Thanks to all for the suggestions.

[topt]

Timing belt don't make noises. Fan belts do.. If it were anything to do with a timing belt they would have to dismantle loads of stuff to get to it, not a five minute job. They re-tensioned the fan belt.

Thanks for that clarification. Makes more sense.