Bigwoody

we have been working on a 98 12v 3500 at my shop that has had some strange problems. It all started a few months ago when the owner called us and said "I think I blew it up". He had it towed on a told us he was pretty sure he over rev'ed it.This truck is an auto with a bigger fuel plate, 5" exhaust,spring kit in the pump, and full gauges. The injectors are stock and he did not change the valve springs upon doing the IP spring kit. It had a dead miss on one of the cylinders so we puled the valve covers and discovered it had bent two push rods, we replaced them and everything seemed fine. Within two weeks the owner reported noticing oil in the coolant, brought the truck back we checked the oil cooler and removed the head suspecting a blown gasket or warped head. The head was only a couple of thousands out and we replaced the head gasket. The truck now still is mixing oil with the coolant and is running through more than a gallon a week (it all appears to be going in the cooling system). Again we removed the head, sent it out to be magnafluxed and checked over again, no problems were found. We don't see any obvious cracks in the block or head. We are sorta at a lose as to what to do next....any help?
On a side note one other problem this truck has had for months was high EGT's under hard acceleration. We had replaced exhaust, put stock fuel plate back in it, changed the probe on the EGT gauge and even checked it with a hand held thermometer, still no changes at full throttle the EGT gauge will rise as fast as the tach all the way to better than 1200. Help please...

Rammin On

Check the oil cooler

Bigwoody

read my post.....already been checked...twice

Box5

Does it have the 53 block?

ratsun

I'm drawing a blank at the moment as to how all the symptoms could be related but wondered.
What push rods got bent? Both from the same cyl? When you had the head off were there any obvious scores in the cyls or signs of piston to valve contact?
I know its uncommon but the autos also have a oil/water trans cooler that could conceivably allow for a leak.

Box5

But the water to oil cooler wouldn't mix into the engines oil, it's just the coolant and trans cooler.

ratsun

Correct, however I did not see in the post that the coolant was in the oil.
I read ~ Within two weeks the owner reported noticing oil in the coolant, brought the truck back we checked the oil cooler and removed the head suspecting a blown gasket or warped head. The head was only a couple of thousands out and we replaced the head gasket. The truck now still is mixing oil with the coolant and is running through more than a gallon a week (it all appears to be going in the cooling system).~ Chances are its engine oil but???

Box5

yea. I think he might be dealing with a 53 block?

kawi600

did he also bend a valve or maybe damage a valve seal? Id run a compression check on the cylinders in question. Those bent pushrods had to have two forces on them to bend, one from the cam the other from the valve / rocker up top being jammed against a piston. Doesnt explain the oil-coolant mix though. Maybe the head gasket isnt sealing like it should? Otherwise the only other culprit is the cooler.
Does this truck have a stock turbo?
I thought a 53 block was cracking on the outside of the block only?

ratsun

I have only seen them leak outside but I guess anything is possible?

Bigwoody

I'll check the 53 block thing. The bent pushrods were both on number 4. It does have a stock turbo. The head gasket appears to be sealing fine (per the second one installed). He did not bend a valve or damage a valve seal, we sent the head out to the machine shop and were told all the guides and seals were in great shape, which surprised us, the truck has over 400k on it. The cylinder bores look practically new still have cross hatch marks in all of them, no ridge etc..We are still drawing a freaking blank...I hate to put this thing back together again without really finding anything causing this problem, thanks for the help so far.

farmer0_1

i know you would look but any cylinders cleaner than the next? check radiator for Co2 traces? at the last stop how about bars leak. we used it alot on external head cracks on mid eightes gas six bangers that gm had , first gm did the warrenty thing but with at least a couple hundred of these in the fleet they were swamped. how about cavitation pit in cylinder wall , maybe number four loaded up with water? just thoughts hope one might help. my jd tractor was swapping oil and water new liners all is better had very small holes thru liner on the inside not visible.