Need to identify a noise - please help

[RCMike]

Hi All,
Any help would be great to identify what this is (hopefully not the turbo itself).

At about 2500/2600 rpm and above (but only under engine load), i have a noise that is a bit like a noise half way between a metallic whistle/screech (hard to describe), more revs (over 2500) - a bit louder and the frequency changes (proportional with rev's). Below 2500 rpm, just get the usual roar type sound - no other noise. Its a bit like switching a switch on at 2500rpm.

I kind of assumed the turbo would be spooled up well before this rpm.

From inside the truck It does sound like it coming from the turbo general area - its not a normal turbo whistle sound however, but is quite loud. All the belts are good, nothing is slipping.

It doesn't happen in neutral if i simply rev the engine - its only under load (also does it in low range up a steep muddy hill - when over 2500rpm).

I can't see any oil/air leaks in the turbo/intercooler hoses etc and the truck doesn't seem to use any oil (at least over the last few hundred miles).

There is loads of power up to 2500rpm, but after that, it then kinds of flattens off.

I do have a K&N air filter, but no snorkel - in any case its not an induction sound.

Its not really causing me a problem as i very rarely need to use high engine revs - but i would like to know what it could be.

Thanks.

 

[solarman216]

that sounds to me like one of your turbo hose clips is loose or maybe a split hose or a leak from the inter cooler, if you have one, did not look at what model you have, Rick

 

[RCMike]

that sounds to me like one of your turbo hose clips is loose or maybe a split hose or a leak from the inter cooler, if you have one, did not look at what model you have, Rick

I checked the hose clips on both sides of the intercooler (left and right), they are all tight - the little stub hoses look ok and not perished. I'll have a poke around again and see if i can spot anything.

I did notice on the turbo side of the intercooler (little stub hose), there is jubilee clips and on the other side there are those spring type clips that but they feel really strong.

Is there an easy way to pressure test it (i.e. with a compressor)?

Or would it be worth replacing the spring clips with jubilee clips?

Cheers.

 

[solarman216]

you probably need to remove the inter cooler and check the hoses for splits, but also if a hose has split you should see oil discharge, Rick

 

[RCMike]

Thanks Rick - I did check for oil and couldn't see any on either the outside of the hoses or the joints but will take the intercooler off and see what the noses look like inside. I'm just about to go away on hols so it may take me a couple of weeks to check.
Cheers.

 

[solarman216]

Also it is not unknown for a manifold gasket to lose a bit, but again look for tell tale oil as all turbo's pass a bit, Rick

 

[RCMike]

Hopefully tracked it down to the stub hose between the turbo and the intercooler - a bit tricky to find and in the end degreased everything and went for a laning trip. All i can see/feel is a very thin layer of oil on the previously degreased stub hose.

So, i'll replace this first along with the clips and see if that cures it.

Question is - the intercooler pipe is ~64mm OD, but the turbo pipe is about 10mm less OD. It doesn't look like the stub hose has a taper - so is it OK to replace this with a std silicon (high pressure) standard diameter hose (off ebay etc) and simply close the gap with the clips - or is it a special tapered hose i need to get?

Second question is about the clips - on the other side of the intercooler, it has very strong spring clips, but on this side (the turbo side), it has garden hose type jubilee clips (i'm never certain they don't pinch the hose on the screw bit) - is it better to get the spring clips or the special looking screw clips that seem to be designed for turbo hoses (at least on ebay they look like special jubilee clips)?

Cheers,
Mike.

 

[RCMike]

Just took the pipe off and measured both ends (Turbo/IC) properly - seems its 56mm straight (no taper) - can't edit the above so just thought i'd post a correction.

 

[AlexD333]

No closer to a diagnostic? :nenau

 

[solarman216]

worm drive clips are the best, Rick

 

[RCMike]

No closer to a diagnostic? :nenau

Hopefully will just be the turbo to IC hose - a new one should arrive in a few days (been away on hols so only just got back to it).

 

[RCMike]

worm drive clips are the best, Rick

Thanks Rick, i'll stick with jubilee clips then.

 

[glanrichbex]

Gearboxes tend to make the whistleing metailc noises you have described - it doesn't mean it's on its way out, they're noisy gearboxes at the best of times.

 

[RCMike]

Small update on this.

I replaced the turbo to IC hose and i think that has reduced the noise a bit but its still there.

So, currently waiting for a new hose to arrive to do the other side (then at least its done). Also, cleaning out the intercooler <not too oily, just a thin film>.

I did try to do a home pressure test on the IC but unable to really get any pressure in it due to not being able to properly seal the big holes at either end.

Did notice that i could get the noise to appear (hardly noticeable - but still there) when simply in neutral - floor the accelerator pedal and then release quickly (rpm needle up to ~3.5k). Need to have the bonnet open and listening carefully however.

I'll continue the diagnostics.

 

[RCMike]

Gearboxes tend to make the whistleing metailc noises you have described - it doesn't mean it's on its way out, they're noisy gearboxes at the best of times.

Forgot to say - don't think its the gearbox as i can get it to make the noise in neutral sat on the drive but i'll listen out for gearbox noises as well.

 

[despot67]

Small update on this.

I replaced the turbo to IC hose and i think that has reduced the noise a bit but its still there.

So, currently waiting for a new hose to arrive to do the other side (then at least its done). Also, cleaning out the intercooler <not too oily, just a thin film>.

I did try to do a home pressure test on the IC but unable to really get any pressure in it due to not being able to properly seal the big holes at either end.

Did notice that i could get the noise to appear (hardly noticeable - but still there) when simply in neutral - floor the accelerator pedal and then release quickly (rpm needle up to ~3.5k). Need to have the bonnet open and listening carefully however.

I'll continue the diagnostics.

did you find out what caused the whistle as mine does exactly the same and its not my exhaust?

 

[daniel2609]

did you find out what caused the whistle as mine does exactly the same and its not my exhaust?

Mike doesnt have the terrano any more, he now has a shogun v6 petrol.

not sure if he sorted it or not, ive just messaged him on facebook, so you might get a reply soon

 

[daniel2609]

this is what he sent me:

The Watergate actuator was weak, I added a second spring to it and that helped. It. It was still there however. I think the milners exhaust made it sound a bit louder as well, but never really managed to eliminate it.

 

[rustic]

this is what he sent me:

The Watergate actuator was weak, I added a second spring to it and that helped. It. It was still there however. I think the milners exhaust made it sound a bit louder as well, but never really managed to eliminate it.

"Waste gate" I think...

 

[daniel2609]

"Waste gate" I think...

probably, i just copied and pasted from facebook