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6.5 coolant problem

crashandburn

crashandburn

1/2 ton status
Joined
Dec 6, 2007
Posts
334
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Location
Colorado Springs, CO
About 6 months ago I broke my own rule and sold a truck to a friend from work. I never sell to people I know, but he loved it and wanted it so I sold it to him. It's a 97 Suburban 2500 and it is the nicest, cleanest one I have ever seen. Only reason I sold it was that I couldn't keep it cool towing uphill, and I live in Colorado, where you might have to go uphill for 20 minutes straight without a flat spot for a break.
About a month ago, he somehow overheated it getting onto the highway. Dumped the coolant bad. Had to put in 5 gallons of water to fill it. Ran fine after that. A week or two later, same thing happened. He checked the coolant the other day and had to add 1.5 gallon. I'm worried that he may have cracked the head and it is using water. Odd thing is that it shows no other symptoms whatsoever.
No white smoke in exhaust.
No water in the oil.
No oil in the water.
No running issues.
No excessive pressure in the radiator.
I know that cracked heads are a common problem with 6.5s (I told him when he bought it, NEVER let the temp get past 215), so I bet some guys on here have cracked theirs. What did it act like when yours did it?
 
crashandburn said:
About 6 months ago I broke my own rule and sold a truck to a friend from work. I never sell to people I know, but he loved it and wanted it so I sold it to him. It's a 97 Suburban 2500 and it is the nicest, cleanest one I have ever seen. Only reason I sold it was that I couldn't keep it cool towing uphill, and I live in Colorado, where you might have to go uphill for 20 minutes straight without a flat spot for a break.
About a month ago, he somehow overheated it getting onto the highway. Dumped the coolant bad. Had to put in 5 gallons of water to fill it. Ran fine after that. A week or two later, same thing happened. He checked the coolant the other day and had to add 1.5 gallon. I'm worried that he may have cracked the head and it is using water. Odd thing is that it shows no other symptoms whatsoever.
No white smoke in exhaust.
No water in the oil.
No oil in the water.
No running issues.
No excessive pressure in the radiator.
I know that cracked heads are a common problem with 6.5s (I told him when he bought it, NEVER let the temp get past 215), so I bet some guys on here have cracked theirs. What did it act like when yours did it?
Click to expand...

Well, our basket case engine cracked the heads and also the block. The block crack allowed combustion gasses into the coolant, so it overflowed and bubbled constantly. Pretty sure you would have noticed if you had this problem. The head crack allowed water into the oil. Also noticeable. If you're consuming large amounts of water and don't think you're leaking, I'd think you could see it in the exhaust. :dunno:

P.S. - The reason I call it the basket case engine is that we didn't find out about the block crack until AFTER I had finished installing new heads. :doah: This remains the most discouraging project I've ever undertaken.
 
crashandburn said:
Oooooo, that hurts.
Click to expand...

Yeah. Crash and burn is an apt description. ;)

That truck (my dad's) had other headaches, too. He wound up horse-trading the new heads for a take-out engine installed by some guy I never met. The new engine runs terribly, gushes oil, has a failed 2-piece flywheel (:doah: :doah: :doah), and somewhere along the line the new injectors that I had installed mysteriously disappeared. I think they stayed in the good heads when the engines were swapped. I also think this "friend" may not have known what he was doing, he seemed surprised that the flywheel had failed. :doah:

Anyway, it turned into a real headache, it's been parked for several years now, and my dad has tried several times to give it to me for scrap value. It will probably get recycled into some future project.
 
Well, radiator shops are disappearing fast, but there are still a few around. Most of them have a combustion gas tester. You put a small hand pump on the radiator cap spout, and suck some air out of the cooling system through a liquid solution.
If there are combustion gases in the coolant from a cracked head, block or gasket, the fluid changes color.

If the engine has a crack, it will show up with that test.
If you can't find a rad shop, I have seen that tester somewhere else. Maybe an Autozone rental, not sure.
 
5 gallons is a lot of coolant loss. Probably wont show anything on the combustion gas test, any bubbles in the coolant reservoir?
 
Good question. There doesn't appear to be a leak, but without creamy oil, or oily water, or white smoke in the exhaust, or bubbly coolant, where else could it go?
 
Maybe out the "pee hole" in the water pump ?..--might be tricking out slow enough only when driving ,hot,that it leaks,and it evaporates quickly,so you see no drpis--though I would think it would show as a stain on the engine at least eventually..

A friend had an engine that cracked a cylinder water jacket (not the bore itself),on the lifter galley side--the leak evidently was slow enough to let the coolant boil off on the lifter galley,it took a long time before the oil on the dipstick showed any moisture...the owner bought a salvage yard engine to swap in its place..the mechanic had to re-use the intake and a friend decided to strip the rest of the engine to get maximum scrap value,and found the crack..

That car had been in his shop several times for overheat issues--tried a new thermostat,radiator,and that didn't help any--also the heater core failed and was replaced,might be coincidence,but it appeared to be clean inside,and looked like it "popped" from excess pressure..
 
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