Bad Turbo?

[MRBarta]

I have been informed that my truck is only producing 17 pounds of boost and that my turbo is bad. I was curious what normal boost is for a '96 6.5 L turbo diesel is and how difficult it is to change out a turbo. Is it as simple as unbolting the old one and bolting in the new one? or are there other adjustments that would need to be made for it to work? Also where is the best place to get a new turbo and are there any modifications or upgrades that would be good to do at the same time? and would the Chilton's shop manual have guidance to changing it?

[GMCfourX4]

If your truck is stock, 7 is more in line with a normal amount of boost.... anything up to 12 is OK without an intercooler... What were the circumstances that someone told you this?

-Chris

[Cowracer]

Originally posted by MRBarta:
I have been informed that my truck is only producing 17 pounds of boost and that my turbo is bad. I was curious what normal boost is for a '96 6.5 L turbo diesel is and how difficult it is to change out a turbo. Is it as simple as unbolting the old one and bolting in the new one? or are there other adjustments that would need to be made for it to work? Also where is the best place to get a new turbo and are there any modifications or upgrades that would be good to do at the same time? and would the Chilton's shop manual have guidance to changing it? Hopfully, the 17# boost is a typo. Typical stock boost is 7# (seven). 17# is excessive and without an intercooler, could be destructive.

Fresh from the factory, these trucks will make about 7# on hard acceleration, but it will only peak there and rapidly fall off. Sounds like yours is ok.

To be sure, WITH ENGINE OFF, rotate the turbine wheel by hand and check for smooth operation. Also check for fore-and-aft movement of the shaft. None (or very damn little) should be noticable by hand


If your turbo needs replaced, it is a fairly straighforward operaiton. Remove oil feed and return lines. Undo the exhaust spigot clamp and intake tube/air cleaner assy. and undo the 4 bolts. Lots of penetrating oil will help. Shouldn't take more than 3-4 hours to change a turbo.

tim

[MRBarta]

I was getting a 236 code and I replaced the boost sensor and was still getting it. So I took it in to get the vacuum measured and it was a bad vacuum pump and wastegate solenoid. So after those got replaced they measured for vacuum and boost and told me it was 17 and should be around the 20's but I think maybe they were thinking of a duramax and not a 6.5, so they said my turbo needed to be replaced and it would cost $2500. So I don't know if they're trying to take me for some money of what but it sounds like replacing the turbo is definitely something I could do and even more it sounds like it's not even bad. The other day the SES light came back on with a 236 code but it only lasted for half a day and now is gone. I'll have to check it tonight for wiggling. Thank you for the advice.

[grape]

FIND NEW SHOP FAST!!!!!!!!!

[Cowracer]

I concur. the only way they would have measured 17 PSI boost was if they were blowing air into it with a hose. Not only are they stupid, but they lied to you.

And on top of that if boost was supposed to be "around 20#" and it was making 17#, that would mean the turbo was good and you probably had a clogged air filter.

Stupid lies are bad enough, Damn lies are worse.

You should post the name of this place as a warning to other members in your area.

tim

[MRBarta]

It was a Pontiac/GMC dealer! that's why I was surprised and they only have one diesel tech and he's replaced my injector pump and then i had them do the vacuum pump and such. i always research the hell out of things before I take it there, so I knew i wasn't getting vacuum and that it was probably the pump, but then the whole turbo thing caught me off gaurd when they told me that becase i knew boost on 6.5's is suppose to be less than 10# especially since my truck is stock. I don't know of anywhere else in the area with a diesel tech worth his own. but, this mean that my turbo probably isn't bad then huh? at least that's good news.

[DmaxMaverick]

Hold one minute!!!

Is that PSIG, or PSIA???

PSIA is including atmospheric pressure, 14.7 at sea level. 17 PSIA - 14.7 = 2.3 PSIG. PSIG is what your "corrected" gage will show you. A N/A engine operates on 14.7 PSI (sea level) intake pressure.

The diagnosis by your tech is probably correct. The Tech II will show PSIA, as will the correct gage if use in accordance with the manual's diagnostic process.

Get more info before you hang that tech.

[rjschoolcraft]

I agree with DmaxMaverick...

14.7 psi atmospheric pressure + 7 psi gage pressure is 21.7 psia or absolute pressure. As stated, the Tech II will display this absolute pressure. Hence, his comment that it should be about 20 or so. Make sure of what he is reporting to you.

[gmenor]

MRbrata
I got a GM-4 that I took off my Burb (went with with a GM-8). There was nothing wrong with it when I took it off. It is yours for the shipping cost. Need to get rid of all the parts I have acquired.

[MRBarta]

Thank you all for your help I really appreciate it! That makes me feel better about the mechanics findings. I was really starting to gain confidence in him too until that. He's the dealers Duramax tech but i wouldn't think that is too much different. Guess ya never know as much as ya think ya do.
What's the difference between the GM-4 and the GM-8?
Is it hard on my engine running it with a bad turbo?
Gmenor, i will gladly take your old turbo. Please let me know how to go about getting it from you.

[Hye]

After replacing a vacuum pump, my turbo was not up to its previous performance. After a couple of weeks, it was back to normal. No guages, just watching the tailpipe out the rearview.

[gmenor]

MrBarta,
Here is my email address
gmenor@aol.com or menorg@orau.gov and send your address I'll have it in the mail or UPS tomorrow. As far as the difference I saw very little. My experience is the GM-4 it had more power on take off but lost some at the higher speed. The GM-8 did not have the same power at take off but seemed to have the power at the passing speed. This is my experience, others can probably give more insight.