Unbareable sound

[300znewbie]

I bought a 1993 300zx twin turbo about 2 months ago. The car had all kinds of power with only one problem; during boost when I would accelerate, the car would make a very high pitched whistle (Not the normal blow off valve whistle). I was told that there was probably a vacuum leak of some kind. I bought the car for 7500 bucks, so I figured it wasn't a bad deal. The car is also stage 4 modified and had a brand new engine dropped in it in 2000 and since then has only had 30000 mile put on it. I figured that is awsome a guy dropped like 10k on this and it hasn't had many miles since.

1. upgraded exhaust
2. Jim Wolf ECU upgrade
3. HKS Blow off valve
3. HKS EVC

I found that there was a tech at the nissan service department, that specalizes in Z cars. When I went for a test drive with him he said " That is not a good sound". After haveing the car for a while I ended up geting a laundry list of mostly small things, but he told me that the right turbo was going and the left one was shot. I had them rebuilt along with most of the other little things repaired.

When I got the car back it was still making that noise and the car was overboosting for a while. I reajusted my EVC and it stopped overboosting. So Now I have dropped like 5500 bucks on this thing and it is still making that noise. It is onviously loosing pressure somewhere, but we can't figure out were.

The tech is still looking at it now and it has been a week since I took it back to him. Friday he said " This is the wierdest thing he has ever come across, but he thinks it may actually be the right catalytic converter".

My question is this:

1. Does that sound right to you experts out there
2. Could it be the HKS SSQV Blow off valve or intercooler making the noise
3. If none of this sounds right. What do you think is causing the noise?

Any help out there would be greatly appreciated.

[k3smostwanted]

Originally Posted by 300znewbie

I bought a 1993 300zx twin turbo about 2 months ago. The car had all kinds of power with only one problem; during boost when I would accelerate, the car would make a very high pitched whistle (Not the normal blow off valve whistle). I was told that there was probably a vacuum leak of some kind. I bought the car for 7500 bucks, so I figured it wasn't a bad deal. The car is also stage 4 modified and had a brand new engine dropped in it in 2000 and since then has only had 30000 mile put on it. I figured that is awsome a guy dropped like 10k on this and it hasn't had many miles since.

1. upgraded exhaust
2. Jim Wolf ECU upgrade
3. HKS Blow off valve
3. HKS EVC

I found that there was a tech at the nissan service department, that specalizes in Z cars. When I went for a test drive with him he said " That is not a good sound". After haveing the car for a while I ended up geting a laundry list of mostly small things, but he told me that the right turbo was going and the left one was shot. I had them rebuilt along with most of the other little things repaired.

When I got the car back it was still making that noise and the car was overboosting for a while. I reajusted my EVC and it stopped overboosting. So Now I have dropped like 5500 bucks on this thing and it is still making that noise. It is onviously loosing pressure somewhere, but we can't figure out were.

The tech is still looking at it now and it has been a week since I took it back to him. Friday he said " This is the wierdest thing he has ever come across, but he thinks it may actually be the right catalytic converter".

My question is this:

1. Does that sound right to you experts out there
2. Could it be the HKS SSQV Blow off valve or intercooler making the noise
3. If none of this sounds right. What do you think is causing the noise?

Any help out there would be greatly appreciated.

ok...the whistling sound would normally not be a turbo going out. you will usually here a grinding sound or something because the turbine shaft gets what we call shaft play, then scrapes the turbo housings when boosting.

what it sounds like to me is that the BOV or wastegate is not holding the boost???

i am pretty sure HKS BOV's are adjustable. maybe the previous owner had the boost set lower on the car and thus had the BOV spring not as tight.

as for the wastgate, you should have had the place you ahd rebuild the turbos test the wastegates to make sure they were holding boost. was the turbo housing cracked on exhaust side. this could release air and is very popular with the Garret GT25's.

also, make sure you check all Boost piping for any signs of air escaping. it could easily be a cracked hose or a loose clamp, etc.

since your losing boost pressure and it only happens when boosting...it has to be somewhere in the boost system.

good luck!!! diagnosing the problem on these cars is 3/4's the battle.

[300znewbie]

Originally Posted by k3smostwanted

ok...the whistling sound would normally not be a turbo going out. you will usually here a grinding sound or something because the turbine shaft gets what we call shaft play, then scrapes the turbo housings when boosting.

what it sounds like to me is that the BOV or wastegate is not holding the boost???

i am pretty sure HKS BOV's are adjustable. maybe the previous owner had the boost set lower on the car and thus had the BOV spring not as tight.

as for the wastgate, you should have had the place you ahd rebuild the turbos test the wastegates to make sure they were holding boost. was the turbo housing cracked on exhaust side. this could release air and is very popular with the Garret GT25's.

also, make sure you check all Boost piping for any signs of air escaping. it could easily be a cracked hose or a loose clamp, etc.

since your losing boost pressure and it only happens when boosting...it has to be somewhere in the boost system.

good luck!!! diagnosing the problem on these cars is 3/4's the battle.

Thanks for the feed back. The sound is not a scrapping but whistle may not be the correct descriptive word either. It sounds like a work whistle, kind of like the flinstones. You can seriously hear it a mile away.

I don't think the BOV being set to low is the problem since it will happen at 5psi of boost when I turn the EVC off.

It sounds like it is seriously a needle in a hay stack searching for the problem. The car is still at Nissan and hopefully the tech will have something for me tomorrow, but I won't hold my breath. The tech says he can hear the noise coming from the right side underneath the car. I was wondering if He could be hearing the BOV's leaking or maybe even the intercooler has a bad gasket and air is escaping from there.

[k3smostwanted]

Originally Posted by 300znewbie

Thanks for the feed back. The sound is not a scrapping but whistle may not be the correct descriptive word either. It sounds like a work whistle, kind of like the flinstones. You can seriously hear it a mile away.

I don't think the BOV being set to low is the problem since it will happen at 5psi of boost when I turn the EVC off.

It sounds like it is seriously a needle in a hay stack searching for the problem. The car is still at Nissan and hopefully the tech will have something for me tomorrow, but I won't hold my breath. The tech says he can hear the noise coming from the right side underneath the car. I was wondering if He could be hearing the BOV's leaking or maybe even the intercooler has a bad gasket and air is escaping from there.

no gaskets on the intercooler but it is probably a boost leak...

the more you discribe it, it sounds like the wastegate isnt holding the boost...but i would check the whole boost system for leaks first.

[ZedEx]

Hook up and Boost Leak Tester... And give that a whirl. We were having similar problems with every single DSM in our race team.

We Boost Tested all 4 GS-X Eclipses, every single one had a boost leak somewhere. After we fixed the boost leaks, no more whistling.

It doesn't sound like you have malfunctioning Wastegates... Perhaps your Blow-Off Valves need to be tightened down a bit? Our Turbocharged LS CRX was whistling tremendously at Wide Open Throttle... Turns out the GReddy Type-S is notorious for this problem... A bit of adjusting, and the car was handling boost like never before.

It sounds like you have a massive boost leak somewhere... Good luck with it man.

-Wes

[k3smostwanted]

Originally Posted by ZedEx

Hook up and Boost Leak Tester... And give that a whirl. We were having similar problems with every single DSM in our race team.

We Boost Tested all 4 GS-X Eclipses, every single one had a boost leak somewhere. After we fixed the boost leaks, no more whistling.

they wonder why DSM's get bad names.

[300znewbie]

Originally Posted by k3smostwanted

they wonder why DSM's get bad names.

thanks for all the help guys. I really appreciate the feedback.

I am a network systems engineer by trade and I know nothing about cars, least of all about 300z's. I am learning though. I am suppose to find out from the mechanic today if he has found anything. This guy owns 4 z's both 300 and 350's and seems to know his stuff. I just know that everyone can not know everything so forums are awsome for getting other peoples takes on problems.

Any one out there from the San Diego area. I would like to make some buddies that are into japanese imports and more so Z's.

Thanks again for the help, if I find anything today I will be sure to let you guys know.

[300znewbie]

Originally Posted by 300znewbie

thanks for all the help guys. I really appreciate the feedback.

I am a network systems engineer by trade and I know nothing about cars, least of all about 300z's. I am learning though. I am suppose to find out from the mechanic today if he has found anything. This guy owns 4 z's both 300 and 350's and seems to know his stuff. I just know that everyone can not know everything so forums are awsome for getting other peoples takes on problems.

Any one out there from the San Diego area. I would like to make some buddies that are into japanese imports and more so Z's.

Thanks again for the help, if I find anything today I will be sure to let you guys know.

well they still don't know were the sound is coming from. After friday it will be 2 weeks and still no joy :-(.

[ExTrEmEDrIfT]

dude im from SD but live in chicago now , what part of Sd you live in?

[300znewbie]

Originally Posted by ExTrEmEDrIfT

dude im from SD but live in chicago now , what part of Sd you live in?

Well I am actually from Bakersfield CA., but I have lived in San Diego since 98. I actually live in El Cajon and have for the past two years. With the rising price for homes, I had to do something. It isn't that bad though.

What made you move to Chicago. I have been there, I was in the navy so I was in Great Lakes and use to frequent Chicago.

[DeleriousZ]

any luck with the problem yet?

[300znewbie]

Originally Posted by DeleriousZ

any luck with the problem yet?

No, there is not luck yet. The guy working on my car has had no joy:-). He and a bunch of the techs at nissan think it is an exhaust leak, but have been unable to pinpoint the problem.

[k3smostwanted]

Originally Posted by 300znewbie

No, there is not luck yet. The guy working on my car has had no joy:-). He and a bunch of the techs at nissan think it is an exhaust leak, but have been unable to pinpoint the problem.

exhaust leak...

did the look at all of the boost piping? don't pay them for running around with their head shoved up their a**. also, another thing...the Turbo Housing itself could be cracked or if they really think it is an exhaust leak, how about the manifolds that seemed to be buried under 50lbs of crap?

[300znewbie]

Originally Posted by 300znewbie

No, there is not luck yet. The guy working on my car has had no joy:-). He and a bunch of the techs at nissan think it is an exhaust leak, but have been unable to pinpoint the problem.

They are not charging me, but I am little pissed because I brought the car in to have the noise checked out and I was told it was because my turbo's need to be rebuilt. they did that and it is still making the noise.

I was wondering about the exhaust manifold myself but I guess the tech says he can hear the noise coming from the right side underneath my car. It makes me wonder if my turbo's even needed to be rebuilt and the guy just assumed they did because of the sound.

[k3smostwanted]

Originally Posted by 300znewbie

They are not charging me, but I am little pissed because I brought the car in to have the noise checked out and I was told it was because my turbo's need to be rebuilt. they did that and it is still making the noise.

I was wondering about the exhaust manifold myself but I guess the tech says he can hear the noise coming from the right side underneath my car. It makes me wonder if my turbo's even needed to be rebuilt and the guy just assumed they did because of the sound.

your turbos probably did not need to be rebuilt. i dont know how he would have gotten that idea by your symptoms. you said its like air blowing out...a turbo needing rebuilt would more than likely sound like a grinder on cement because of the extensive shaft play.

if your turbo housing itself is cracked on once side then all of the pressurized air would leak out of that crack making a loud blowing sound. but then again, a small boost leak anywhere could possibly make that sound.

i am yet to hear and exhaust leak make the sound your are describing. but if it is exhaust...i would think it is the manifold. and tell the guy that the exhaust manifold is underneath the right side of the car.

anyways, tell him to check the AIV hoses that connect to the midpipes. maybe they arent clamped tight.