1998 V70 R AWD Whistle/whine on acceleration- need opinions

craywm · Post by **craywm** » 08 Oct 2015, 15:55

Hello all,

I posted this over at V70r.com but not a lot of traffic there now. Here's whats going on:

So, quick back ground. Earlier this year I burnt 2 valves. First one went in January, second one went in May. Decided to rebuild my top end. While I was down there, I wiggled my my turbo shaft and decided to rebuild that too. Turbo was balanced by a shop. All parts are original Mitsubishi parts. Just finished putting it back together and started her up on Sunday. It ran great all day (I decided to take a 100 mile drive the day I started it up). The drive was highway speed, 70 miles of 65-70 mph on cruise with no boost. Around the 70 mile mark I decided to pull off and check out a small town. 2 miles off the exit, I noticed a loud whistling sound that fluctuated with rpm. I thought maybe I had a vacuum tube lose or something so I didn't think anything of it.

I've driven it another 30 miles now (just to work and back) and still have the same sound. I have NO loss in power. After the turbo rebuild and adjusting my throttle/wastegate, my power is great! checked all my fluids, and they were all good. engine isnt over heating.

The sound is ONLY present in drive with the gear selection in the "D" position. I tested park and neutral with no luck. So I figure all that info rules out the turbo, and since its only making the sound in drive, that would rule out the engine bearings. I started thinking this could be a transmission bearing but I dont know what that sounds like.. Also, I have not changed my transmission fluid (since I bought the car, who knows when it was last changed). Also, I removed my prop shaft so I'm running FWD only. I thought also since my transmission is strong, could it be that my transfer case and bevel gear sprung a seal and is dry now? I figures that could produce an rpm related whistle as well, plus the volume level in the cabin would point to it being closer to the cabin area than the transmission.

I have not been able to identify where the whistle is originating from since it only happens in drive and I cant exactly sit under the hood at 30 mph. So my questions are:

1) could this be the transmission? What in the transmission would make this noise?
2) could a dry transfer/bevel gear cause this type of noise?

I've taken a few low speed videos of the sound. I know what normal turbo operation sounds like. All I've ever driven my whole life has been Volvo 5-cylinder turbos. I'm fairly certain this isn't a turbo issue. Here's the youtube link to the video:

<iframe width="420" height="315" src="https://www.youtube.com/embed/XPrxB91WZh0" frameborder="0" allowfullscreen></iframe>

Here is a link to a second video I made, the CEL is for a P0455:

<iframe width="420" height="315" src="https://www.youtube.com/embed/D8reJNFo7ak" frameborder="0" allowfullscreen></iframe>

In light of the CEL code, I thought maybe my exhaust manifold was not properly fastened downstream of the turbo and that I could be hearing the turbo spinning through the exhaust leak. I'll be checking into that.

Thanks for all the help in advance!
Cray

Bluevanacd2005 · Post by **Bluevanacd2005** » 08 Oct 2015, 18:23

It sure seems like it is related to the turbo. Listening to the video and watching the tachometer, the noise lags behind engine speed just a little. Would also make sense it doesn't do it in park or neutral, because the engine is not loaded enough to really spool the turbo?

Those are my thoughts. Check for leaks like you said...

Spenser

craywm · Post by **craywm** » 09 Oct 2015, 05:09

I think rpm is rpm. So if the engine is spinning at 3600, the turbo is spinning too, regardless of load or not. But, there it could be linked to loading is when the engine moves. It must move slightly under larger load so if there were some type of exhaust leak, I guess its possible it could "flex" in a way to accentuate that and make it larger. I noticed when I had cruise control on that if I was going down a hill at the same speed/rpm as going up, the noise was not present. When I got to the bottom and started going up (atleast before the tanny downshifted) the noise immediately started. So I think it does have something to do with load.

Of course, then you have to also look at the awd. If more load was on the front wheels, then more power may be sent to the rear wheels. So the transfer case could be making the noise (or where my awd prop shaft connection comes out). But I doubt that would be rpm dependent after all the reductions.

I did, however, see an article that supported the turbo theory. The D5 turbo's seem to have this issue as well. I found a few videos showing it. They said it pointed to the blow off valve. But, I have no loss in power and it doesn't happen in neutral..

Do turbo's produce boost in neutral and park? I don't have a boost gage currently

Sommerfeldt · Post by **Sommerfeldt** » 09 Oct 2015, 06:02

Just to chime in on the turbo thing - there's a reason for turbo lag - you need exhaust pressure to spin the the turbo, to make it produce boost. W/o enough exhaust pressure, a turbo engine is an NA engine, hence the vacuum in the engine.

So no, the turbo doesn't produce boost in N or P.

- S

Post by **erikv11** » 09 Oct 2015, 08:28

So if you are whistling along at 40, let off the throttle and and ease it into neutral, then the sound goes away? Even if you then rev in neutral?

craywm · Post by **craywm** » 09 Oct 2015, 08:55

But the engine is still producing exhaust gasses in park and neutral, and those exhaust gasses pass by the turbine blade. So the blade must be spinning, which means the compressor wheel is spinning too. Unless in park, the wastegate opens all the way, or all the pressure from the compressor is bypassed. Of course, you would have to rev it some to produce exhaust pressure and induce boost on the intake side, so if I rev it in park and neutral - shouldn't I hear the same whistle from the turbo?

At 40 in neutral, the sound is very faint. I think what I hear is normal turbo operation. You can see that in the second video I posted where I put it in Neutral at 30 or so and rev the engine.

When I rebuilt the turbo, I used all Mitsu parts and had it balanced/checked by a reputable shop (dieselinjectionco). I trust that they did the balance/check correctly since that's pretty much all they do. Thats why I thought it could be the blow off valve or wastegate, since I did touch both of those as well.

craywm · Post by **craywm** » 09 Oct 2015, 10:37

I just realized how ignorant I've been. While on lunch break, I drove the car again and popped it into Neutral. I could slightly hear the noise again, probably because its getting worse. But I noticed when I pop the car into neutral and hold the throttle at the same position the RPMs skyrocket.. Obviously the turbo doesn't spin fast at all in park or neutral because the rpms climb too fast to produce enough pressure. With a load though, the throttle can open more and the pressure is enough. I am now thinking it is a problem with the turbo, especially since I rebuilt it not 1 month ago.. Looks like I'll be in the market for a new cassette. I'm going to use a mechanics stethoscope first though. maybe I can hear something in park or neutral, but engine noise is drowning it out. hope I haven't torched my turbo too much yet if it is the problem.

Any other ideas?

Sommerfeldt · Post by **Sommerfeldt** » 09 Oct 2015, 12:06

Well... the rpms don't have anything to do with it - it's about producing enough exhaust gases to make the turbo spin. You can easily have low rpm, floor it and have the turbo spool up even so. The exhaust pressure spins the turbo, and the car goes from being an NA to a turbo car - i.e. the car sucks air in while the exhaust pressure is low, and then the turbo pushes air in once the exhaust pressure is high enough to spin the turbo at a rate where it moves more air in than the vacuum can suck. Then you've got positive pressure.

Another option is to get a cheap-ish sport filter, and get rid of your air box - that way you can everything the turbo does. Mine sounds like a damn jet with the open filter. You might even want to leave it like that once you get the problem fixed.

Or, take it to a dyno to run it under load while stationary.

- S

craywm · Post by **craywm** » 12 Oct 2015, 09:26

I took my intake out again and found my intake tube had a notch taken out of it. I dont think it is effecting the sealing though. I thought at first that I may be able to hear the turbo operating (and unfiltered air was being sucked into the turbo) through the notch, but I don't think this is the case now.

I can now hear the noise at high rpms in park and neutral. I will be tracking it down later this week. I'm thinking if I need a new CHRA, I will order it from Midwest turbo. Does anyone know if they are a reputable supplier? Not sure if I trust the Ebay CHRA replacements. Sucks that my rebuild was no good. In the future, I suggest to all to just order the new CHRA as its only $350 and you know its good.

Post by **erikv11** » 12 Oct 2015, 10:01

You will have to compare pricing but FYI a super reputable turbo supply/rebuild outfit is G-pop Shop, I have heard plenty of endorsements and never a complaint about them.

For that kind of coin I might first swap in another turbo just to make sure the sound goes away. But maybe that is too much of a PITA on an AWD car, I must confess I haven't swapped one of those.