Turbo Dead
 

Well, my $500 dollar '87 300D has been feeling sluggish off and on. Tonight I attached a gauge to the manifold port for the ALDA, revved 'er up and got...a...negative...reading. :grim:

Sooo, I pulled the bellows hose off of the turbo inlet and reached in to spin the wheel and... it turned :confused: However after fiddling with it some more, it was clear it wasn't turning as easily as I would expect with a healthy turbo and would intermittently bind, especially if I put any more pressure on one side of the wheel than the other. I grabbed the end of the shaft. No fore/aft play. But, if I pulled up and down on the end, the side-to-side play is pretty significant.

Oh wise forum. What sayest thou? Advice? Good cheap turbos for sale?

Thanks in advance.
-Louis

well if your turbo is truly kaput just slap on a good forum parts section replacement or search the junk yards

is the oil supply good? is your wastegate working? more info is needed to determine if a turbo is needed. but binding is NOT a good sign...

My turbo doesn't turn as easily as I would think.
But that wasn't the problem for my down level of boost.

I added an aftermarket manual turbo boost controller ($20 ebay) and now I can dial in way too much boost if I want to. I don't, no point to it. I do have it set to about 0.9 atmosphere boost. I have also added boost gauge in the car to watch things.

ZOOM power is back on the highway. Couldn't get over 120kph before, now I'm scared to push it harder than 160kph just because of the age of the car, but it will go there - more pedal and more pull remain unused.

Problem is/was a soft wastegate spring, pretty sure. The boost controller side steps the issue, and nothing is easier than splicing a piece of plumbing into the wastegate hose that is external to the turbo. 10 minute job.

You could try pinching off your wastegate hose (or just pulling it off) and go for a short drive. If that addresses the problem do what I did. You'll know by 3000RPM if this is making a difference. Careful, a good working turbo can produce 3 bar with the hose off. Waaay too much boost for the car.

If that doesn't address the problem, maybe your wastegate is stuck open. Check the linkage for binding, travel. You can use compressed air (regulated to 20 psi or so!) into that wastegate hose to move the wastegate you should hear it smack shut when you take the air away. Even so, the flapper inside might still be shutting on something instead of making a seal. Any air going through there is less for the turbine (compress side)... less boost.

My feeling that it is bad is based on the binding issue. I can think of no reason why a properly working unit would bind at any time. Dunno if the oil supply is good. If it is not, I would imagine enough damage would have been done already that it would need to come out anyway and will check the oil supply at that point. The engine itself has good oil pressure, but I suppose the line could be blocked, somehow.

A point I failed to post is that I was initially turning it in the direction that it would be turning if the engine were running. It would bind off and on, but I would be able to overcome and continue turning. However, when I decided to try it in the other direction, it moved a bit and then stopped and I was unable to overcome the binding. I had to turn it the original direction again to be able to turn it. Something just ain't right here.

I'll try to do more checking tomorrow starting with trying to see if the wheel spins with the engine running. Then moving on to pulling the wastegate hose etc.

There isn't enough exhaust flow or heat without a load on the engine to get the turbo wheel spinning in a meaningful way.

Sixto
87 300D

I should be able to at least see it spin with a good tromp on the accelerator pedal with no load, though, yes?

It should be spinning even with the engine at idle.....at least all of ours do on the 617 engines.

If your turbo shaft won't turn both ways, you must have parts stuck in there. Acting like a ratchet.

Or a rock :D. Was the engine off but hot when you turned it by hand? With no or cold oil it will be stiff, low oil might lead to "binding". Binding should incurr a heck of a lot of noise.

That's what I was thinking.

Last night, the engine was off, but had been run recently enough that it was still relatively warm. There had/has been no noise whatsoever from the turbo, which is why I thought it might be seized, originally. I was mistaken. :o

Tonight, I cranked 'er up and pulled the turbo inlet. It was spinning at idle, even cold. I can't explain the binding or stopping while turning by hand. It certainly didn't seem to be having trouble spinning with the engine running (not that I'm complaining). I won't have time to play with it any more tonight, but I plan to concentrate on on the wastegate/controls.
Scott, sounds like your setup might be worth looking into.

Yup sounding more like a wastegate issue. Next step is yank the pressure line on the wastegate and go for drive to test the soft spring idea.

Like I say, my turbine is not easy to spin by finger tip pressure. It certainly does not 'freewheel' when spun. You have to push it around in circles and when you stop it stops. And it seems there are "stiffer" spots when pushing it around. No matter, I still get 1 bar pressure boost out of this thing with the manual boost controller.

I think the boost controller actually compensates for both issues: stiffer rotation and soft spring, by keeping more exhaust pressure on the turbine longer before wasting any.

You didn't mention if you have the ALDA on the car or not. I nearly yanked my turbo once thinking it was a culprit when instead a failing ALDA was causing driveability issues with power. To make the long story short, yank your ALDA off while you are diagnosing power issues before zeroing in on what you think is a turbo issue here.

I know it's tight for space on this car to remove ALDA completely but you can just unscrew the big nut and allow ALDA to ride up so it is just resting / wobbling on top of the IP. That's good enough to experiment. From the front of the car, you can get a long handled big flathead screwdriver blade on the square part of the ALDA and just whack the end of the screwdriver to rotate the ALDA... you may or may not need to hold the big nut with a 27mm open end wrench when you do this. The screwdriver alone was enough to crack the threads of the nut, then I was able to spin the nut by hand.

An in-op turbo symptom is usually an in-op boost enrichment.

First, the turbo spins on a film of oil, no oil flow means it might not have that film, which allows it to touch metal, and have significant drag. Also allows some radial play.

The wastegate has a mechanical arm, very hard to see, on top of the turbo assembly. I have seen two with that arm disconnected on the turbine side, which would allow the wastegate to stay open.

Back to the load enrichment failure. You need to check the fitting on the intake plenum near the washer-bottle, blow through it to ensure it is clear, check the overboost protection / switchover valve on the inner-fender (connected to the aforementioned fitting) the same way (should go in the bottom fitting), then be sure that the center fitting from that valve (a solenoid valve actually, N.O.) goes to the top of the alda (through a Y). You can also temporarily run a line directly from the intake plenum to the ALDA to see if that makes it run properly.

This is posted about once a week, that's about how often it comes up.

Where exactly did you plug into the vacuum system? You should T it off of the line from the manifold. The stock config has a line that goes from intake manifold to an Overboost protection valve on Firewall near the fusebox. Often times it is plugged up which will cause no boost or low boost. Bypassing it is safe...mine has been bypassed for 2 years.

Yeah, I would love to have been able to pull the pressure line last night, but I have had to put off work on the car probably until sometime next week (really busy).

The car still has the ALDA, but I wasn't suspecting it so much since it was blowing black smoke going up hills. Doesn't the ALDA suppress fuel delivery until it is pressurized by manifold pressure? If it were the ALDA and the manifold had proper pressure from the turbo, I wouldn't expect to see a lot of smoke, would I? I mean, if the turbo is adding air, but the ALDA isn't allowing the IP to deliver enough fuel, you wouldn't see a lot of smoke, just a power loss, right? (I'm just trying to make sense of all this).


I guess part of my problem is my unfamiliarity with this particular turbo unit. The only one I've ever changed was from a Subaru and they spin very freely. There would be no question that if it stopped while you were still physically turning it, there is a serious issue.
The wastegate arm is intact. All the plumbing is clear (as I posted previously, the ALDA port is where I measured manifold pressure ,or lack of, originally and it did vary according to throttle position.)


I may do the bypass thing at some point temporarily for troubleshooting, if nothing else.

Thanks all!
Louis