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Turbo whine problem solved[700/1987] posted by Dan on
Tuesday, 23 November 1999, at 7:32 a.m.
In a previous post, I mentioned that my turbocharger started to make an unusual whining/whirring noise. I had resigned myself to the fact that a new or rebuilt turbocharger was eventually going to be needed. This past weekend I was checking out the car in preparation of traveling during the upcoming Thanksgiving holiday when I noticed some oily residue on an induction component. After wiping off the oil, I noticed there were two allen bolts which were very loose. I tightened the bolts and now the turbo whine is gone and performance is great! I don't know what this part/assembly is called as it is not pictured or even mentioned in my Haynes manual. Perhaps one of you fellow bricksters can tell me. I'll try to describe the assembly from memory, as I don't have the car in front of me now. It is located between the turbo and the intercooler, mounted on a bracket at the front left side of the engine. A vacuum line from the intake manifold goes to what looks like an adjustable diaphram on top. There are a couple of hoses that connect to the assembly. One comes from the large diameter hose coming out of the turbocharger. The other goes to the large diameter hose coming out of the air box going to the turbocharger.
Re: Turbo whine problem solved >>>CBV<<<[700/1987] posted by Ed O'Briant on
Tuesday, 23 November 1999, at 9:21 a.m.
Sounds like you are describing a common problem with the compressor blow off valve on the "older" turbo cars fitted with a Garrett unit.
Ed O'Briant
Re: Turbo whine problem solved >>>CBV<<<[700/1987] posted by Leon Ramseur on
Friday, 26 November 1999, at 8:39 p.m.
I have a Turbo whine problem on a 1990 760 but I can't find the pop off valve like on an 1987. Where is it on a 1990 760?
Re: Turbo whine problem solved >>>CBV<<<[700/1987] posted by Ed O'Briant on
Saturday, 27 November 1999, at 9:37 a.m.
Leon-
Your '90 760 most probably has a Mitsubishi TD40H turbo. The compressor blow by valve is integral to the turbo, and not a separate piece like those found on earlier turbo cars fitted with Garrett turbos. There should be a vacuum line from the intake manifold to the CBV. This line runs over the valve cover and connects to the CBV. The CBV is bolted to the turbo compressor side (towards front of engine) with three bolts. Make sure these bolts are tight.
Whining can also be indicative of worn bearings and/or damaged (bent, chipped) fins in the center cartridge. Check for any leaks, tears, loose clamps, etc., with the intercooler and turbo plumbing as well. While there, I would check the condition of ALL vacuum lines.
If you have removed any obstructions from within the air box (foam, plastic horn, etc.) and/or have freed up the exhaust, the turbo will spin much easier and will consequently be louder. Hope some of this helps.
All the Best-
Ed O'Briant
willtown@mindspring.com