Delica Canada | Mitsubishi Van Club

Here is the problem, I have been chasing some noise that I originally thought was squealy belts on my alternator. a couple sets of belts later and making sure they are well tensioned, I still have my squeal. it happens when the van is under moderate acceleration, and when I am coasting and the rpm is dropping, I cannot duplicate the fault in neutral, just by revving the engine. nor does it do it when the engine is cold. I am starting to think that squeal is more of a bearing squeal, so here are my choices:

alternator/ vacuum pump, however its not constant or at a steady rpm, so that seems to rule that out. could be another bearing in the belt systems but it does not sound correct when compared to the engine speed itself,

last option, which is starting to sound more likely, is the turbo bearings, if its developed play in the turbo it could be either the bearings themselves making the noise or the turbine/ compressor wheels contacting the housing from the axial play. In my mind if the turbo is spooling unloaded it wont move in its housing very much so it wont be as likely to contact the case, however if the turbo spools under load it will want to shift in its housing causing something to contact, or the bearings to load up enough to cause a noise. also it seems to correlate with the turbine spooling down after it loses pressure from the exhaust, but it only makes noise a second or so after you have released the throttle, and does it in two sort of pulses. I can still hear the turbo whine normally though, which is why I am not so sure about it. It also will make the noise when i apply throttle but below the rpm the turbo spools at.


I hate chasing mystery noises, it is very frustrating, especially because I cannot duplicate it with the van in neutral, so I cant be looking around under the hood really while driving.

any thoughts?

Could be rear end noise...

It sounds like it is coming from the engine bay, I am going to pull the intake hose and see if I can get at the compressor wheel on the turbo to check the play in the bearings. I might rig up a temporary boost gauge too to see if my boost pressure is changing when I hear the noise

Found a problem, hopefully this is what is causing the noise. The gasket between the intake manifold and turbo adapter is leaking, there is oil and nastiness all over the turbo as a result. I pulled the intake hose and looked at the compressor wheel. no play that i can feel, but minor foreign object damage to the tips of the compressor blades. not enough for me to warrant buying a new turbo. I will order a new gasket and clean it up, and hope for the best. at least all I have to do is loosen the hose on top of the turbo and pull the two bolts on the intake manifold. I started the engine and revved it up and could see oil and air bubbling out of the seam of the mating surface of the intake manifold.

Just for someone's future reference; there is one other area that can cause a squeaking (reciprocal). The timing belt tensioner bearing can be going bad. I have seen this happen in the 4G64, so I presume the 4D56 could have the same issue.

If the tensioner starts doing this, you don't have long before it come apart and the timing belt looses tension.

oh wonderful, is there any way to check it with things taken apart? the problem is that I cant get it to make the noise with the engine in neutral. so no leaning in the engine bay revving it up to hear where its coming from.

you could take the belts off the alternator briefly.
if the noise goes away then its obvious... its a bearing in the alternator...
good luck

Yokohama wrote:Just for someone's future reference; there is one other area that can cause a squeaking (reciprocal). The timing belt tensioner bearing can be going bad. I have seen this happen in the 4G64, so I presume the 4D56 could have the same issue.

If the tensioner starts doing this, you don't have long before it come apart and the timing belt looses tension.

this is a VERY good point.
I just lost my tensioner/bearing and seal at the last CVI meet.

I was lucky because it was on CCA warranty.
It could have cost me all my belts, and possibly engine damage.
I cannot stress how important this is. you want to look into this IMMEDIATELY.

I just recalled an annoying squeal I had a few years ago that turned out to be the plastic shroud that covers the belts. It had distorted over time and started to contact one of the belt pulleys. I think the lads just trimmed out a bit of the plastic and sent me quietly on my way.