Engine Coolant Hot

speedstarv · May 21, 2009

I have looked through all the posts.. here is my issue..

2005 1500 Z71

About every 6 weeks I get a coolant hot message and end up adding coolant to the system. I have had 2 different mechanics go over the truck. No leaks found.

Pressure tested the system and its good. Replaced the rad cap. Replaced the thermostat. Flushed the dexcool out and used the universal coolant. My head is spinning with this. Been told either the system is boiling the coolant away or the water pump could be leaking out of the weep hole, but no signs of a leak? Makes no sense. No drips. No pools or puddles. No stains... Also heard that a cylinder head may be the culprit, but yet again.. no signs?

Should I just shoot it or shoot myself? The truck only has 54k miles.......

Bish · May 21, 2009

How much coolant you loosing? Gasket failing can leech coolant into combustion chamber and/or oil. Send a sample of your oil out for analysis and they will tell you if you have coolant in it. Is your oil level high or does the oil look milkey at all? Also if you have white smoke out the tailpipe chances are you are burning coolant.

speedstarv · May 22, 2009

How much coolant you loosing? Gasket failing can leech coolant into combustion chamber and/or oil. Send a sample of your oil out for analysis and they will tell you if you have coolant in it. Is your oil level high or does the oil look milkey at all? Also if you have white smoke out the tailpipe chances are you are burning coolant.

Thus far.. no coolant has been found in the oil. I used to work in a local lube shop and it's just oil.. thought about a head gasket, but without seeing anything in the oil, kind of rules it out don't you think? I go through a bottle to 2 bottles every 6 weeks.. it has varied here lately

CapitalTruck · May 22, 2009

Do a search for bulletins about Castech cylinder heads that get cracks in them and allow the coolant to be burned away. There's a little symbol inside that will let you know if that is a Castech brand head.

C & A s Dad · May 22, 2009

My bet would be the water pump or the water pump gaskets. An 05 should have the revised o ring style gaskets which are pretty bullet proof. I would suggest your leak is the WP because a slight leak from the weep hole is very hard to detect. It seems to dry or evaporate before it makes it to the ground making it almost impossible to find.

It could also be a head or head gasket and coolant would not be detected in the oil without an oil analysis.

I would go for the pump first. If this does not fix it, add a bottle of Bar's Leaks. Not as a permanent fix but just to see if your coolant stops disapearing for a few weeks. If so, you likely have a head or head gasket issue.

Bars Leaks is by no means a fix for a head or head gasket issue but it wil typically stop the leak temporarily and it will not hurt anything in your system.

MS3DALE · May 22, 2009

Do a search for bulletins about Castech cylinder heads that get cracks in them and allow the coolant to be burned away. There's a little symbol inside that will let you know if that is a Castech brand head.

If not the water pump like Trey mentioned,It will probably be this ^^^^^ the cylinder heads themselves.

mrkleen · May 22, 2009

I have the exact same problem with a 2005 GMC 1500 crew cab. I have had 2 places check it out (it has a water pump less than 2 months old) with both scatching thier heads. My heads have 706 stamped just underneath the valve cover i have read that people have had problems with them. Sorry to jack your thread just odd we have the exact same problem. Let me know waht you find out.

speedstarv · May 22, 2009

I have the exact same problem with a 2005 GMC 1500 crew cab. I have had 2 places check it out (it has a water pump less than 2 months old) with both scatching thier heads. My heads have 706 stamped just underneath the valve cover i have read that people have had problems with them. Sorry to jack your thread just odd we have the exact same problem. Let me know waht you find out.

Well I am definitely going the lesser expensive route right now and replacing the water pump. I just wish I could find a high performance pump for the 5.3L. Nobody seems to make one....

cujo8 · May 22, 2009

How much coolant you loosing? Gasket failing can leech coolant into combustion chamber and/or oil. Send a sample of your oil out for analysis and they will tell you if you have coolant in it. Is your oil level high or does the oil look milkey at all? Also if you have white smoke out the tailpipe chances are you are burning coolant.

Thus far.. no coolant has been found in the oil. I used to work in a local lube shop and it's just oil.. thought about a head gasket, but without seeing anything in the oil, kind of rules it out don't you think? I go through a bottle to 2 bottles every 6 weeks.. it has varied here lately

What size bottles are you talking about here? I typically see antifreeze sold in 1 gallon bottles, so if you're going through 1 to 2 gallons of anti-freeze in a six week period that is a lot. If all that was going into your crank case you wouldn't need an oil analysis to detect it, your oil level would be very high and would look very milky. If you're burning it up in your combustion chamber(s) you should be seeing white smoke coming from your tail pipe. So there must be a leak some where, but I'm surprised you have not seen signs of a leak with that much coolant missing! Changing your water pump is probably a very good idea at this point and this is probably a good time to change your hoses as well. It still bothers me that you don't see signs of coolant leak (Drips/puddles), since coolant is not very volatile and should stick around for quite awhile. I would get a hold of a compression tester or leak-down tester and test each cylinder to see if you find any low readings or leaks.

henryupinhere · May 22, 2009

i would agree with most of the posters, you need to check your water pump and gaskets, but i also had a problem like that on my friend's truck. bought some of that ultraviolet dye and later checked it, he had a small leak in one of the coolant hoses that runs thru the throttle, might want to give that a check before you go out and put yourself thru hell with the water pump

Norseman · May 22, 2009

My bet would be the water pump or the water pump gaskets. An 05 should have the revised o ring style gaskets which are pretty bullet proof. I would suggest your leak is the WP because a slight leak from the weep hole is very hard to detect. It seems to dry or evaporate before it makes it to the ground making it almost impossible to find.

It could also be a head or head gasket and coolant would not be detected in the oil without an oil analysis.

I would go for the pump first. If this does not fix it, add a bottle of Bar's Leaks. Not as a permanent fix but just to see if your coolant stops disapearing for a few weeks. If so, you likely have a head or head gasket issue.

Bars Leaks is by no means a fix for a head or head gasket issue but it wil typically stop the leak temporarily and it will not hurt anything in your system.

Yep, Water pump.

Draenor · May 22, 2009

I'm with the others. Try the water pump. You can also try dying the coolant and running a black light over the engine to detect leakage. As Jim stated, if you are going thru the 1 to 2 gallon jugs in a month, you should be able to see something. Either the oil analysis or the compression test should indicate the head leak.

slayer305 · May 22, 2009

What about a intake gasket or valves leaking? I had a 87 Monte Carlo SS that had valve stem seals leaking for years then all of a sudden blew both head gaskets. No coolant visible in the oil until the end.

Draenor · May 22, 2009

Intake is dry, no coolant.

speedstarv · May 22, 2009

I have the exact same problem with a 2005 GMC 1500 crew cab. I have had 2 places check it out (it has a water pump less than 2 months old) with both scatching thier heads. My heads have 706 stamped just underneath the valve cover i have read that people have had problems with them. Sorry to jack your thread just odd we have the exact same problem. Let me know waht you find out.

Seems like we definitely have the same issue. I went ahead today and swapped the water pump and gaskets. Only time will tell right now if that was it. Got my fingers crossed right now.

My heads also have 706 stamped on them. If it turns out to be the heads, with the price GM wants for them, I will definitely yank this motor and swap it with something better.