Cooling System Headache

D

DirtyMaxx03

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May 22, 2011
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Not a huge Dmax board but i'll try this here too

So i thought the truck had blown head gaskets because the low coolant light would always come on and i was always missing coolant.

Well i replaced the thermostats and i think that fixed the missing coolant problem (was spewing out of the overflow i guess) however the light will still come on.

I can be driving for 20 minutes and the truck will not heat up at all, heater wont work, truck sounds like crap. Then all the sudden the temp gauge will shoot up to 180* and the truck sounds better but the heater wont blow hot.

Eventually the heater will start working but almost at the exact same time the heater starts blowing hot, the low coolant sign will come on the DIC.

I can stop the truck and turn it off and check the coolant and it will look real low, as soon as i pop the cap and relieve pressure, the coolant level will rise to where its supposed to be.

Its like the cooling system is over pressurizing itself or something.

HELP
 
Do a pressure test on the coolant system that might help tell you if you're leaking somewhere, if the system is in fact over pressurizing there's a goof chance you popped a gasket and have exhaust pressure leaking over to coolant side
 
I know its acting like blown head gaskets, but im not losing coolant anymore. No milky exhaust smelling coolant either.

Also, i can put my truck on a 600+rwhp tune and flog the hell out of it without any coolant disappearing. If the thermostats are not functioning correctly, can that cause any of this?
 
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It doesn't have to leak in the exhaust to have a blown hg, it can leak across into the coolant system I'd almost put money on betting its a blown hg from hearing the symptoms
 
All i know is i plan on getting a new truck soon, so if i tear into this one to install studs and the gaskets are fine, i'll be pissed that i just wasted $1000 of down payment money.
 
do what the guy that i bought my duramax from did... throw in a bottle of that crap that "fixes the head gasket leak" LOL..
 
Very understandable, from my experience I stick with my previous answer it sounds like a hg to me, there is cheap ways to check to verify what I said is really going on
DirtyMaxx03 said:
All i know is i plan on getting a new truck soon, so if i tear into this one to install studs and the gaskets are fine, i'll be pissed that i just wasted $1000 of down payment money.
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Looks like I'll pressure check the system. Really didn't wanna sink a couple grand into this truck right now.
 
How many miles on the truck? Is the upper hose hard? And does it hold pressure over night? Rarely do these things show any sign of intermix when they have a failed HG.
 
TheBigNasty said:
Sounds like you may have some air trapped in the cooling system.
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2 people have mentioned this. Neither one dmax savy, both were old heavy duty diesel mechanics. They were the reason for this thread. Another guy said my heater core could be clogged to ****.
1pieceatatime. said:
How many miles on the truck? Is the upper hose hard? And does it hold pressure over night? Rarely do these things show any sign of intermix when they have a failed HG.
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Yup all the signs of head gasket failure on a dmax. Except none of them are consistent. I've experienced most of the symptoms but they occur a couple times and go away, then something else acts up. I thought my truck fixed itself until we had a freeze and it was real cold for a few days then it started his **** again.
 
The truck can be at 180* and the heater won't blow hot. The second I smell the heater turn on I can watch the temp gauge rise to 210 and a couple seconds later it will flash the low coolant message on the dic.

That's what has me thinking it's a thermostat (maybe I got a dud) or heater core, or something like that.
 
Bleed the system good via the bleeder on top of the thermostat housing, replace or test the cap and drive it. After its up to temp feel both heater hoses and make sure they are equally hot. If ones hot and ones cold your heater core is plugged.
 
Bustedknuckles said:
Bleed the system good via the bleeder on top of the thermostat housing, replace or test the cap and drive it. After its up to temp feel both heater hoses and make sure they are equally hot. If ones hot and ones cold your heater core is plugged.
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Thanks brotha. I totally forgot about the bleeder, fml. And I've been meaning to replace the cap.
 
DirtyMaxx03 said:
The truck can be at 180* and the heater won't blow hot. The second I smell the heater turn on I can watch the temp gauge rise to 210 and a couple seconds later it will flash the low coolant message on the dic.

That's what has me thinking it's a thermostat (maybe I got a dud) or heater core, or something like that.
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Sounds like something more than a headgasket. I have worked on a few of em now and none of the trucks with bad headgaskets had any noticeable cab heat or overheating issues as long as they weren't low on coolant.

FWIW, I bought my lb7 under the pretense that it had a bad headgasket, upper hose would stay hard, but it pushed out very little coolant. I drove it and sled pulled it max effort tuned for a year before we finally tore it down to find the tiniest separation on one of the gaskets.
 
You have combustion pressure getting into the cooling system. When the stats finally get coolant to them the air pocket gets purged and your heat comes back. Put a jug on the hose coming out of your coolant tank and I bet you wil lfind it is pushing coolant out.
 
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