bigragu

Just thought I'd post this up as it seems there's been a few on here lately. I am curious to know, in a truck in stock form to mild horsepower increase, what causes these to go other than high boost pressures? I've heard the capacity to not exceed in boost for a Cummins head gasket is around 40-45 psi, constant. What about mileage/age? Is that also a contributing factor? I guess what I'm wondering, is if a plane Jane daily driver with no racing whatsoever and max boost numbers to be around 35 psi is still prone to HG failures.

I know one day a HG replacement is probably inevitable, and if there's anyone with crazy high mileage numbers, with the original HG still in place and stock head studs, please post your experiences.

Thank you

1972RedNeck

My current '93 had 220K is bone stock and it started seeping coolant down the block. I installed a new Cummins gasket and Fastenal head bolts and plan to juice it up this winter.

My previous '93 was stock when I got it and I modded it and was pushing an easy 300+ HP and 45 PSI of boost and the original head gasket never offered to fail.

KRB

At 200K now, mine never saw over 24lbs boost and it was stock other than fuel turned up when I got it at 90K.

I've done everything in the sig but never hot rodded and drove like an old man (which now, I am) but it did pull loads.

Still, at around 175K or so it started leaking coolant on the passenger side between #5 & #6. Why? Who knows, but in the process of rebuilding I discovered my radiator was partially plugged so maybe I had been running higher than normal temps for a while? But it never ran hot or overheated until the day it sprang the leak pulling a gooseneck load of hay.

N. Besonderes

Around the water jacket in the front right corner, below the thermostat, as well as around the water jacket at the opposite rear left corner, seem to be a weak point. Once coolant starts seeping between, corrosion does its thing and next thing you know, you have Niagara Falls.
Mine started just after 300K.
No doubt big boost contributes to it but I think you should just expect it to develop a leak at the corners once it starts coming into the prime of its life.

-Niemand

torquefan

The most common leak I've seen is simply an external coolant leak at the front corner under the thermostat housing. I've never believed it to be related to excessive boost pressure, as it is a leak between the coolant passage and the exterior, as opposed to a leak between the combustion chamber and the coolant passage. It seems to me that the leak area is just really close to the outer edge of the head, and the factory gasket didn't have a really large sealant bead in that area. Comparing the factory gasket to a replacement gasket, you can plainly see that the replacement has been reinforced by a bead of sealant that is much wider in that spot than the original gasket.

KRB

[QUOTE=torquefan;3336919]... I've never believed it to be related to excessive boost pressure, as it is a leak between the coolant passage and the exterior, as opposed to a leak between the combustion chamber and the coolant passage...QUOTE]

That's what mine was doing, just a different spot. I never compared the head gaskets. Maybe same situation, just a different location?

bigragu

Partially plugged on the exterior fins, or inside the radiator itself?

bigragu

I wonder if anyone has super high mileage first gens, like say past 300 in mileage, that are running strong on the factory HG and factory studs.

oliver foster

Yes I have a couple of those that seem to be still running the factory head gasket.
One '92 I have has 526,xxx on it. It fires right up and runs great.

bigragu

Thanks, Oliver, as that's good to know. Shows promise, lol.

nascar mark

It’s not always boost that blows the head gaskets, although it can be a combo of things. On the higher mileage engines with factory installed head gasket, the thousands of heat cycles over the years cause the head to move around slightly (expansion & contraction), which causes the compression rings of the head gasket to wear grooves in the head & block. These wear groves can eventually allow even stock cyl pressures to push past the compression ring and cause gasket failure too.
Over heat the engine in any way, excels this wear even faster.
Re-torquing your factory head bolts/gasket by loosening one bolt, half turn loose, then torquing to 132ftlbs (no need to do the factory procedure at this point/age of factory bolts/gasket)..... one bolt at a time is a good idea. Just be careful you don’t stretch your factory bolts. If you feel any stretch at all, stop.

Foxmxrcer

Augie,
My truck had over 300k (estimating 310 or 320k, odo died with the previous owner around 280, 8 years before I bought it) and had the stock head gasket. Truck was completely stock and untouched. I blew the gasket with the thd fuel pin and unknown amount of boost(gauge stopped at 30psi).

bigragu

Your truck is a "power" wagon, lol. Was it during one of your tows with that rock climbing beast of yours?

Foxmxrcer

Negative. Was a cold morning on the way to work, playing on the highway, the day after installing that fuel pin worth the 57mm/14cm hx35. I did blow the boost tube off the turbo this weekend while hauling the Jeep back home....35psi, plus a steep grade, extended period of time.... Luckily I had tools with me. Still need to roll beads in my plumbing.

MAC702

This.

My 96 leaked here after 200k. There is a reason that Cummins supplies an "upgraded" gasket when you purchase the replacement.