240 240 squealing noise under acceleration

This afternoon my 240 developed a fault where I will intermittently hear a loud squealing noise when the engine is under load/acceleration.
When it happens, the car loses a lot of power, is reluctant to rev, and it once even produced some smoke out the exhaust.

It sounds like it's coming from the back of the engine somewhere, kind of of near the flame trap.

I don't think its injector related as I unplugged the two rear injectors one at a time and it made no difference.

It's very intermittent - the car can go back to normal within 30 seconds, and then play up again.

Any ideas ?

(1992 240, manual, LH2.4)
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Comments

  • jamesincJames (@jamesinc) Oz Volvo Ice Fortress
    Does it rev but not make power? That could be the clutch going. Otherwise I'd just go round the hoses looking for leaks. To lose power it would need to be a relatively large hose, like brake booster or larger.
  • 240240 (@240) Canberra
    Nah definitely not clutch I don't think.
    It's almost like it went even rev properly, it's kinda like the engine is bogging down or something.
    I was planning to go over the hoses but surely the problem would be constant if it was vacuum related?
  • If the cat rattles maybe it is split and blocking the exhaust flow.
  • 240240 (@240) Canberra
    I'm about 98% sure that the noise is pinpointed to the top rear part of the engine, and I'm not sure how anything exhaust related could cause noises there...
  • carnut222Greg S (@carnut222) Daylesford VIC
    Cam bearings failing - odd though as it probably woudn’t be intermittent.
  • 240240 (@240) Canberra
    Yeah I mean pretty much everything I can think of wouldn't be intermittent.
    Would cam bearings cause a loss of power?
  • carnut222Greg S (@carnut222) Daylesford VIC
    240 (@240) wrote: »
    Yeah I mean pretty much everything I can think of wouldn't be intermittent.
    Would cam bearings cause a loss of power?

    I guess if there’s enough friction? What about something like A/C compressor or alternator? Again though, loss of power? Odd. Not a fuel line blockage? Something odd with the fuel pressure regulator?
  • 240240 (@240) Canberra
    edited April 20
    Something odd with the fuel pressure regulator?

    This did actually cross my mind, as the car was hard to start (cranked for longer than usual) at one point earlier in the day.
    I actually have a spare fuel pressure regulator so maybe I should install it and see what happens

    Edit - I was thinking of fuel pump check valve, not pressure regulator sorry.
  • carnut222Greg S (@carnut222) Daylesford VIC
    Hmm, I guess it could also be fuel pump (are you sure noise is coming from engine compartment?) Check valve shouldn’t have any impact on how it’s running (unless it’s getting blockage, but it’s on output side of pump so anything that makes it thru the pump will be pretty tiny!
  • 240240 (@240) Canberra
    I'm pretty sure the noise is from the engine (almost sounds like from inside the head) but I guess it could be possible that it's a noise caused by fuel starvation from a dodgy pump?
  • carnut222Greg S (@carnut222) Daylesford VIC
    I guess if the pump is dodgy and not putting out enough flow, the pressure reg could be acting a bit like a wind instrument reed as it goes fully shut, trying to make enough pressure? You could test that theory by briefly blocking off the fuel return hose with some clamping pliers. If the noise doesn’t stop immediately that won’t be it, and don’t leave the return hose blocked for long or the fuel pressure will become excessive if the pump is not faulty, and could cause other issues. This sounds to be a bit unlikely though??
  • 240240 (@240) Canberra
    Well I may have solved this, I'll know for sure tomorrow when I drive the car some more.

    I noticed that the #4 spark plug lead was quite loose, and pulled off the plug quite easily. I looked more closely and the end of the plug was horrible and brown, as was the inside of the lead where it connects to the plug.
    The #4 plug is consistent with where I was hearing the squealing noise from.

    This evening I replaced the spark plugs and put on a 2nd hand set of spark plug leads. What concerns me is the condition of the plug:

    60szrbayv6vj.jpg
    yw7fmgjgl1ud.jpg

    there is some sort of build-up on the plug. Any idea what could cause this?

    It is also present to some degree on the other plugs, and there was a little oil on plugs #1 and #3 as well.

    s8yxk2vm0ezz.jpg
  • carnut222Greg S (@carnut222) Daylesford VIC
    Hmm, maybe loose plug wire arcing? Guess if it isn’t burning the mixture properly due to weak spark it could cause the build-up?
  • carnut222Greg S (@carnut222) Daylesford VIC
    edited April 27
    Def time for new plugs...oil on threads could just be from leaky cam cover gasket.
    Edit: oops, missed that you replaced the plugs - all good!
  • 240240 (@240) Canberra
    Maybe, it's odd that it's on all plugs though if that's the case though.
    I did end up with a big vacuum leak last year as the intake manifold gasket had a hole, so the mixture was out for a while which may have caused some damage...

    Anyway I'll see how it goes with the new plugs, hopefully the same thing won't happen.

    (I haven't been driving the 240 much the last few months as I recently bought a C30, I swear it's giving more problems now that I'm driving it less....)
  • 240240 (@240) Canberra
    The other thing I should mention is that I replaced the spark plugs about 45,000km ago. At the time, the old ones I pulled out still seemed fine. So whatever caused this must be a relatively recent thing (and obviously if still present I want to fix it)
  • 240240 (@240) Canberra
    Well I spoke too soon, the noise is still there.

    I have been advised that the condition of the spark plugs was caused by lean running conditions. So could it be the case that if not enough fuel is getting through (eg a dodgy pump), this is causing the injector(s) to run 'dry' when under load, hence the noise (and hence the condition of the spark plugs)?
  • carnut222Greg S (@carnut222) Daylesford VIC
    240 (@240) wrote: »
    Well I spoke too soon, the noise is still there.

    I have been advised that the condition of the spark plugs was caused by lean running conditions. So could it be the case that if not enough fuel is getting through (eg a dodgy pump), this is causing the injector(s) to run 'dry' when under load, hence the noise (and hence the condition of the spark plugs)?

    How’s the fuel filter?
  • 240240 (@240) Canberra
    I replaced it around the same time as the previous spark plugs, so about 45,000km ago.
    I have a spare I can put in but surely a filter should last longer than that.
  • carnut222Greg S (@carnut222) Daylesford VIC
    240 (@240) wrote: »
    I replaced it around the same time as the previous spark plugs, so about 45,000km ago.
    I have a spare I can put in but surely a filter should last longer than that.

    Yeah I’d think so...hmmm...guess it could also be in-tank pump issue?
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