stock boost level/ignorant mechanic

[45acp]

I need some help here guys, and i pre-appologize for the long post. My father and i co-own the 98 6.5 in my sig. Last week it blew a head gasket and dumped enough coolant in the motor to hydrolock it. Motor was rebuilt by local GMC dealership that has (at least i thought) one of the premier light truck diesel mechanics in my area. Here is the conversation pop and i had while ago...

dad- "Well, he called and said it was ready. He also said there was a problem with something on the turbo. Whatever it was, he fixed it and its running 15psi now like it should."

me- ...long pause... "Um, ok, but thats not right. You cant run that much boost on that motor. He is thinking of a PSD or Cummins. The 6.5 has too much compression and no intercooler. As ive told you before, it should only be around 6psi stock. We cranked it up to 9psi and i told you that was about as far as we could go."

dad- "Well, he's not only a diesel mechanic buy trade but he's also one of the best around. You are just reading crap on the internet...

me- "Well, ok, uh did you get a warranty with that motor?"


Pops tows 20k+ with this truck regularly. Should i start taking bets on how long this $5k rebuild will last? What do i do? To him the diesel mechanic is god and i am just some punk who saw something on that "there interwebnet thingy". Its got boost and EGT guages, but he never looks at the EGT (i know this for a fact).

What the hell do i do now?

[whatnot]

If it is really running 15psi then it will turn on the SES light and cut back fuel unless you have a boost fooler.

I run 12 to 15 PSI on mine. (smokes a lot if I lower it any)

[gmctd]

Might be in your best interests to find out exactly what the guy did to increase Boost to 15psi.

Have him open the hood and show you, point by point.

[ 05-27-2004, 07:15 AM: Message edited by: gmctd ]

[Turbine Doc]

Ditto to what GMCTD said check what he did to get the improvement, no way for a stock 98 to make 15 psi boost without some mods and setting a code & having PCM clip boost/fuel, now if the guy wired the WG shut, or bent the needle on the gauge you might see 15. You would still set codes though unless PCM reflashed to ignore them or a boost fooler is installed.

PS your Dad may want to spend some time here as well lot of folks here with BTDT knowhow driving and operating the 6.5 daily. The dealers Diesel tech may not even own one. Plus since the 6.5 went out of production few dealers have folks that KNOW 6.5s, many people with generic knowledge of Diesels.

The 6.5 is kinda unique to own one is a love/hate thing. Hang around here and you will come across lots of good tips, I've had mine since 2000, this site and the folks here have helped immensely.

[moondoggie]

Good Day!

Parroting what others have said here on the Page, 15 psi without an intercooler is a bad idea. Even with everything done right, at 15 psi you'd be driving with one eye on the pyro all the time.

I have no direct personal knowledge of such, just lots of reading here on the Page over the years. Do a search on your previous posters on this topic - they're The Real Deal, & know what they're talking about.

Blessings!

Brian Johnson, #5044

[45acp]

Thanks for the comments. It just reassured what i thought i already knew. One more thing to add- the dealer mech. said that boost gauges are never right and are usually so far off they are worthless. This along with everything else has me thinking this motor aint gonna last. How the heck could he do a quality rebuild job yet show ignorance on so many basic levels? Oh well, it gets picked up today so we'll see..

[whatnot]

I just noticed that you said you had cranked it up to 9psi before. If you put a turbomaster on it, the mechanic might have thrown it away and put a vacuum actuator back on and he doesn't really have any idea what boost it is running.

[45acp]

Yes, it has a TM on it. The mechanic himself said that its running 15psi now. I just got off the phone with pops, and he "got on it" on the way home in 5th gear and said that it was pulling past 13psi on the gauge. Guess ill go down there this weekend and at least see what the mechanic did... :rolleyes:

[moondoggie]

Good Day!

It's too bad you've already got a boost gauge. I think I'd remove the scale, paint it, then re-scale it with Lettraset (sp) to read about 2/3 of reality. In other words, at 10 PSI boost, the gauge read 15 PSI.

Blessings!

Brian Johnson, #5044

[BigDiesel]

How about an update on this.

[45acp]

Sorry, i meant to get back to you guys sooner.

The truck is not running 15psi, its running about 9 (were it was before it went in for the rebuild). The mechanic had stated that boost guages are so inaccurate that they are worthless, so i can only assume he thinks 9psi on the gauge is really 15... either way it runs great and is NOT running 15psi so nothing to worry about. Needless to say im not too confident in this guy's rebuild since he's shown so much lack of knowledge, but we'll see. Its getting hay season and dad will soon be towing overloaded on a daily basis.