I have 1994 C3500 Crew Cab dually and I've been having hard time with wastegate operation.
Symptoms are:
Truck works ok when eng, temp. is under normal running level,but when engine temp reaches over 170 degrees and I stop on lights etc. and let boost go down, the boost stays 0 psi until engine is cooled down again.

I have new vacuum pump, cheked all lines, temp sender is been checked as well intake as air temp sender, MAP sensor and vacuum solenoid works ok too.

No trouble codes stored, in ecm,

What I should check next? Could it be ecm?

...What I should check next? Could it be ecm?

So far from what I've read from other posts, and experienced first hand, it's the wastegate solenoid. They seem to go bad often in the 6.5TDs. I have a WGS on order to replace my bad one. Until the part gets here, I used a bit of Liquid Wrench to loosen up the little ball inside the solenoid, shook it a while, and then flushed it with carb and choke cleaner to clean it out. I had to do this about 6 times to get the solenoid to operate properly, but it does for now. I hear that this is only a temporary fix to the solenoid, but it works for now...No black smoke on take off and I can feel the turbo kick in now. :ro)

WG solenoid is troublesome, can be intermittent and common, also inexpensive.

Could be a ruptured vacuum pot in the WG actuator or leaky vacuum line too.

To test the pot, just unhook the vacuum line from it, put your finger over the hole and pull the rod out, it should hold vacuum indefinitely, if you can feel is leaking out, it needs to be replaced.

Yes, I am aware that solenoid is most common thing to fail on these systems,and when I started trouble shooting I started on this solenoid.
I can't figure out howcome this problem is so temperature related ?
If solenoid is bad, it should give same problems not deped on engine temperature?
Why wastegate actuator works perfecly ok when engine is cold?
Vacuum leak is ruled out, I have MityVac tester and no leaks,
Today I took thermostat out and engine stayed under 180deg. and boost worked fine .:confused:
Well ,I am gonna get a new solenoid first thing tomorrow , let's see if this unsolved mystery disappears when I soaking solenid in WD40:rolleyes:

....
I can't figure out howcome this problem is so temperature related ?
If solenoid is bad, it should give same problems not deped on engine temperature?
Why wastegate actuator works perfecly ok when engine is cold? . . .


Like oil and water, heat and electronics don't mix. Doesn't matter if it's the WG solenoid, or the PMD. It's pretty much as simple as that.

BTW, ever take the truck for a run - even a short one, but where its gets to norm oper temp (NOT) - then stop and pop the hood? Careful what you touch - metal or plastic - it's all HOT. The continuous cycling from cool to hot and back to cool takes it's toll on electronic components. I know a guy that carries a can of "Freeze Mist" for just such ocassions.

Since you hava an F engine, you could always remove the vacuum actuator from the turbo and modify it into this:http://dieselplace.com/forum/attachment.php?attachmentid=3906

QM, you have mail. I sent you a PM. :help:

QM
What kind of spring tension are you using? I like the simple design. I realise you adj the tension by watching the boost gauge, but I need a starting point. I was going to mod a pressure actuated WG (from a KKK turbo) but yours looks easier.
Also how high can you go with everything stock, and not trip codes?... 10psi??
Nick

...Well ,I am gonna get a new solenoid first thing tomorrow , let's see if this unsolved mystery disappears when I soaking solenid in WD40:rolleyes:

What was the outcome Finn?

I replaced my solenoid today and my SSDiesel Intake came also. Installed them both and, "WOW!", she's running like a raped ape now. :ro) I have a smooth running powerplant. I am very happy with the outcome. I can feel, and hear the turbo kicking in now. Especially on the hiway. :D

my SSDiesel Intake came also. Installed them both and, "WOW!", she's running like a raped ape now. :ro) I have a smooth running powerplant. I am very happy with the outcome. I can feel, and hear the turbo kicking in now. Especially on the hiway. :D
Very reasonably priced intake but do yourself a favor and make a sheild so it only sucks in outside air instead of underhood (HOT) air):h

Very reasonably priced intake but do yourself a favor and make a sheild so it only sucks in outside air instead of underhood (HOT) air):h

Thanks for the suggestion. Any other suggestions on how to fabricate a shield for the intake? I thought of this also, but I'm short on the creative side to fabricate stuff like this. :( I looked at the old intake box and tried to figure something out, but the intake is oval instead of round. I have also thought of getting a short length of PVC, along with another 90* elbow, to place the filter right next to the fender intake. How do ya think that will work? Thanks again. :cool:

Plastic would be better than metal as it doesn't conduct as much heat. Whatever you use, make one out of cardboard first so you don't butcher your final material.

What was the outcome Finn?

I replaced my solenoid today and my SSDiesel Intake came also. Installed them both and, "WOW!", she's running like a raped ape now. :ro) I have a smooth running powerplant. I am very happy with the outcome. I can feel, and hear the turbo kicking in now. Especially on the hiway. :D

Still running w/o thermostat, I contacted local GM dealer for solenoid, yup, they have it for $100 Censored for $35 item
I ordered it, among other stuff from U.S., just have to wait 'till next week.
If this on/off boost problem still exist after solenoid replacement I go for spring & wing nut set up
, I really liked the simple design of it.
Just wondering about getting some extra psi, well I pulled my heads last january and it was something that I don't wanna do frequent basis.
Maybe I stay stock boost figures:rolleyes:
Also, I do have Banks downpipe, Magnaflow catback, and when I read some of you guys comments about catalytic converter , I am planning to " open it up"
Here in Finland we have yearly safety & emission inspection, hopefully I don't open can of worms smoke wise?
Thanks all for comments, this is really great site

Oh yeah, the WD40 treatment didn't help either

Here in Finland we have yearly safety & emission inspection,hopefully I don't open can of worms smoke wise?


Removed my CAT and have no smoke problems.

Here in Finland we have yearly safety & emission inspection, hopefully I don't open can of worms smoke wise?

No smoke when mine got lost either

Me either.