Turbo works sporadicaly 85 300SD - Page 3 - PeachParts Mercedes-Benz Forum

stephenc03 · #31 12-13-2008, 04:00 PM

Quote:

Originally Posted by Jeremy5848

Assuming you teed into the boost line just before ALDA, that should be correct. You should also try teeing into the line before the overboost solenoid; it's possible that the solenoid is broken or clogged, hence not allowing boost from the intake manifold to get to ALDA.

Jeremy

I checked the solinoid by blowing into one side and I got air out of the other....is it reasonable to assume that the solinoid is working correctly?

Jeremy5848 · #32 12-13-2008, 04:03 PM

Quote:

Originally Posted by Brian Carlton

. . . Unless you cut a hole in the exhaust manifold that's at least 1" in diameter, no exhaust leak will have any meaningful effect on the boost. It might delay the onset slightly, but, above 3000 rpm..........you should be well into the wastegate range and the turbo is dumping excess exhaust.

When I had an exhaust leak due to a broken flex line (exhaust manifold to EGR valve) it definitely delayed turbo spool-up. Repairing (and ultimately, replacing with your EGR kit) the pipe made a difference in what I could see with my boost gauge. As you say, ultimate boost pressure did not change but it definitely was quicker to get there once I had fixed what had seemed to be a very small leak.

Another item that delays onset of boost is the trap catalyst. With the 'test pipe' installed in place of the trap cat, my '85 300DT is definitely more responsive.

Jeremy

stephenc03 · #33 12-13-2008, 04:06 PM

Quote:

Originally Posted by Jeremy5848

When I had an exhaust leak due to a broken flex line (exhaust manifold to EGR valve) it definitely delayed turbo spool-up. Repairing (and ultimately, replacing with your EGR kit) the pipe made a difference in what I could see with my boost gauge. As you say, ultimate boost pressure did not change but it definitely was quicker to get there once I had fixed what had seemed to be a very small leak.

Another item that delays onset of boost is the trap catalyst. With the 'test pipe' installed in place of the trap cat, my '85 300DT is definitely more responsive.

Jeremy

When i originally installed the straight pipe about a month ago, I had quick response and seemed to have alot more power. I might have the sam HP but she got up to speed in a hurry compared to the trap...
stephen

coonerboy · #34 12-13-2008, 04:07 PM

Can you remove the "U" tube and see if the turbo spins freely?

stephenc03 · #35 12-13-2008, 04:09 PM

Quote:

Originally Posted by coonerboy

Can you remove the "U" tube and see if the turbo spins freely?

it doesnt have a u-tube beacuse it is a california car....but i did check to see that both sides of the turbo spin freely and no movement side to side or backwards to front....
-Stephen

Jeremy5848 · #36 12-13-2008, 04:23 PM

Quote:

Originally Posted by stephenc03

I checked the solinoid by blowing into one side and I got air out of the other....is it reasonable to assume that the solinoid is working correctly?

I think so. An additional check that you could do is to put 12 Volts on the electrical connectors and see if you can no longer blow through the valve.

There should be an additional port in your intake manifold sealed with a threaded plug. You can remove it and install a fitting, then run a line to your boost gauge. It will tell you if there is boost in the manifold, period. If not, there is a turbo problem; if there is boost, then the IP is for some reason not being "told" to give the engine more fuel – a clogged/broken/leaking fitting, hose, solenoid, or ALDA.

In the following picture, see the port on the side of the intake manifold ('85 300DT ex-CA) just forward of the red cap on the transmission dipstick and behind the overboost pressure switch. The plug in that port can be unscrewed with a metric Allen wrench and replaced with a 1/8" pipe thread fitting with a hose barb. Then run a hose to your boost gauge.

Remember that you will get no boost revving the engine in the driveway, or at most a very little bit at ~4000 RPM. The only way to be sure is to drive the car while keeping half an eye on the boost gauge.

Jeremy

stephenc03 · #37 12-13-2008, 04:50 PM

I tapped into the intake manifold and attached a 1/8" male barb nipple and still the same reading 0 at 3000 RPM and 1psi at 3500 RPM. where do I go from here?
-Stephen

Jeremy5848 · #38 12-13-2008, 08:15 PM

Stuck-open waste gate?

stephenc03 · #39 12-13-2008, 08:43 PM

Quote:

Originally Posted by Jeremy5848

Stuck-open waste gate?

What do I have to do to fix it? or do I have to replace it?

coonerboy · #40 12-13-2008, 09:36 PM

Based on what it looks like in Jeremy's engine pic, just to the left of the wastegate actuator and turbine housing are 4 nuts that attach a pipe/ flange to the turbine housing. If you can get that pipe off, you should be able to see the valve flap that dumps the exhaust when the wastegate opens. If you see its propped open then you found the problem. You may be able to free it up by repeatedly opening and closing the valve. You might also want to get some PB Blaster and lubricate the shaft.

stephenc03 · #41 12-13-2008, 09:54 PM

Quote:

Originally Posted by coonerboy

Based on what it looks like in Jeremy's engine pic, just to the left of the wastegate actuator and turbine housing are 4 nuts that attach a pipe/ flange to the turbine housing. If you can get that pipe off, you should be able to see the valve flap that dumps the exhaust when the wastegate opens. If you see its propped open then you found the problem. You may be able to free it up by repeatedly opening and closing the valve. You might also want to get some PB Blaster and lubricate the shaft.

That pipe doesnt connect to the turbine house....it is actually below it and makes it look like it is attached.
So i can take that plate off? i dont want to screw anything up....stephen

Brian Carlton · #42 12-13-2008, 10:05 PM

Quote:

Originally Posted by stephenc03

I tapped into the intake manifold and attached a 1/8" male barb nipple and still the same reading 0 at 3000 RPM and 1psi at 3500 RPM. where do I go from here?
-Stephen

Was the vehicle accelerating at maximum power in third gear when you obtained this reading?

stephenc03 · #43 12-13-2008, 10:10 PM

Quote:

Originally Posted by Brian Carlton

Was the vehicle accelerating at maximum power in third gear when you obtained this reading?

yes...it could excelerate more but i didnt want to push 4000RPM...it didnt sound healthy

coonerboy · #44 12-13-2008, 10:11 PM

Quote:

Originally Posted by stephenc03

That pipe doesnt connect to the turbine house....it is actually below it and makes it look like it is attached.
So i can take that plate off? i dont want to screw anything up....stephen

This don't attach to the turbine housing?(area circled in red)

stephenc03 · #45 12-13-2008, 10:18 PM

Quote:

Originally Posted by coonerboy

This don't attach to the turbine housing?(area circled in red)

No sir not at the plate where the wastegate is but underneath it does.....it is an after market "straight pipe" where the trap. cat. used to be. the pipe continues underneath and attaches itself to the turbo underneath.
-Stephen