Hey all,
I have just acquired a 1989 D350 5sp. This truck was has been moderately bombed: 3200 spring, Old Smoky fuel pin, fuel screw turned, AFC modified, HTT Stage 3 w/12cm wastegated housing, a BHAF, 3" crossover intake pipe (non-ic'ed truck), a valet switch, and a 4" turbo back exhaust. Truck runs very well and has 266,700 mi. on the clock. My question arises from the erratic behavior of the temp gauge. (the truck also has pre-turbo pyro, boost, and tach gauges) Under normal driving conditions (max 2200 rpms and the valet switch engaged), the temp gauge has begun to slowly rise until it reaches "Hot"...my egt's remain between 500-800 degrees, oil pressure is normal, and there seems to be no excessive heat, and no smoke from the hood as well as no burning smell...the radiator is slightly low on coolant, but the resevoir is completely full (to the cap)...the engine compartment is covered in a fine mist from the overfilled resevoir...I have no idea why this temperature rise is happening...faulty temp gauge?...please advise!

thanks,

BlackBanshee

 

It sounds like the radiator might need flushed to me. Just a thought though, I am not a mechanic just a tinkerer.

 

Could be that the thermostat it stuck closed or at least mostly, not allowing coolant to circulate?

 

Stick an aftermarket temp gauge on it first. I had radiator rotted, replaced hoses, thermostat twice, etc. Still having problems, put a water temp gauge in, stays at 180 while my oe gauge flies all over. Dont throw parts at it like I did.

 

Change your radiator cap for good measure. Could definately be a possibility. Or go to autozone and borrow the tester and test the cap right there.

 

thanks guys, I'll try those ideas and report back...

BlackBanshee

 

okay.....no good news....the thermostat was stuck closed...and the heat pushed the coolant out of the overfill outlet. the truck apparently got pretty hot...what i thought was a manifold leak appears to be a headgasket leak...guys i'm not gonna lie, i am worried. the truck seems to run fine, but i am petrified of head cracks or anything else...anything i should know/look for?
thanks,
blackbanshee

 

Sounds very familiar... are you in NC or get it from someone in NC?

 

99 times out of 100 its just a bad gasket and the head is fine. Both of my turcks and a few others I have seen had the gasket leaking out the rear pasenger side to the outside and down the motor, went almost 3 years on the 92 befor it got bad enough to change and has ben over 1 year on the 96 ( more of a seep than a leak on both). If there are no bubbles in the rad or water in the oil Just have the head checked and put in a new gasket, flush the cooling system, and drive it for another 300k miles

 

Thanks for the advice...that's what i'll do...Caver Dave, I purchased this truck from BigWaylon, a dtr member in Charlotte...it was listed in the dtr classifieds...i reckon you know Greg...I didn't mention the previous owner because I didn't want anyone to think I was blaming him for the leak...i think Greg's a good guy and he sold a good truck...thermostat worked fine when i bought it...my bad on the headgasket....
keep it coming!
BlackBanshee

 

While I've never met him (that I recall), I do know of him and concure that he's a standup guy. However, I *have* seen this truck in person (secretly wanted it even though it was non-I/C ) and agree that stuff just happens to 20 y/o vehicles...

I'm curious about your worry of head damage, but don't recall ever reading about it to being an issue... even with blown head gaskets (as 545 eluded).

Chock it up to another case of Cummins "doing it right the first time"...

 

Even though my mechanic told me that the head was probably fine, i worry about it because a friend of mine blew his headgasket and his head was cracked all to pieces...his truck was really modded though...i really need to set the wastegate on this thing...with the valet switch disengaged this truck will make about 43 psi...that's alittle much i think?

 

I'd be more concerned about the turbo than the head gasket at 43 psi.

 

i hear ya wanna, what's the safe range for a htt stage III?...my guess is about 30-35 psi?..it'll do about 30psi with the valet switch engaged, which is more than enough for my daily driving needs..i have actually only driven it once with the switch off...good God this thing will go...i didn't realize what kind of boost it was making at first, trying to stay on the road and all......what're your thoughts wanna?

 

I wouldn't want to run it over 40 psi. Let the EGT be your guide, start at 30 psi and go up until the EGT stops dropping.