Loosing coolant

[Boog]

My 06 crew cab with 5.3 has been loosing coolant for a few months. It's been gradually getting worse. So far I have not been able to locate the source of the leak. I was adding a quart a week and it's now up to near a gallon in less than a week. It does not drip on the concrete. It's not leaking from the heater core inside the cab. It doesn't appear to be getting in the engine oil. About the only place left for it to go is the combustion chamber. We never smell antifreeze. The engine runs great and we get no codes. It has about 130,000 miles on it. The one thing I have not checked this week is the tranny fluid. If the coolant was getting into the tranny cooler the fluid would register high and surely by now it would start slipping and acting up.

[Gumby]

maybe rent / borrow

Radiator Pressure Tester Kit

so its under psi but not running, hot coolant burns

[Boog]

We have an appointment with a local shop next week. Maybe they can find the source.

[stepside67]

on my 2001 suburban I had the following leaks which were hard to detect. Check the water pump, the gaskets are known for failing. you might also check the quick connect plastic connection to the heater core. I also had a the seam on the radiator side tank leak with a hairline crack

[DjS71]

Was water pump for me, but not in that high of volume.

[Beetle]

Replace the radiator cap, should fix it

If not pressure test it. You may have a leaking freeze plug...

[Boog]

It's up to a gallon per week right now. No signs on the engine, frame or on the pavement where we park it. New rad cap already. Engine oil and trans fluid still pretty as can be.

[Special-Ed]

I don't know if this is accurate or not. And I can't remember where I heard it. So someone please let me know if this is right or wrong.

Gasket failure on intake can put coolant right into air/fuel mixture and it gets burned in combustion cycle.

[wahl4m]

i have had that problem /its the intake gaskets !!!! common on all newer trucks !! usually the "check engine lite will come on with a senser -upper intake code ? "

[Boog]

Originally Posted by Special-Ed

I don't know if this is accurate or not. And I can't remember where I heard it. So someone please let me know if this is right or wrong.

Gasket failure on intake can put coolant right into air/fuel mixture and it gets burned in combustion cycle.

This is true of the earlier Vortecs but not the 99 and ups. They have a dry intake as in no coolant passes through the intake manifold on these. thank you though.

[Boog]

Well the truck went in for testing. They pressure tested the system then ran a bore scope in the cylinders and found #3 & 5 were white inside instead of black. That's where the coolant was going. The oil level is now well up on the stick too. Also apparently coolant doesn't make the engine oil milky like it used to or is it just water that does that?
It's time to yank the heads and fix this thing.
They found a tsb regarding coolant loss and it mentioned something about certain aluminum heads and a drainback tube going through a coolant passage leaking. They didn't say whether it's something that can be resealed or if a replacement head is required.

[Boog]

Well it turned out to be a cracked head. You can't even see it. The shop sent it to another shop to check it and found nothing. Then sent it to another shop that specializes in head work. He pressure tested the head and it showed up. He marked where it was bubbling out. It is around a headbolt hole.
I've had the truck for 2 years and it's never ran hot. It's been driven daily mostly by my wife and she is easy on it. It has 130,000 miles on it.
Both heads were checked, only one was bad and it will be going back together tomorrow. Mama is getting happy again.