My CUCV keep losing coolant and I don’t know where. It had some radiator issues a while back but didn’t seem too serious.

Here’s the rundown.

The radiator had a slight split seam a while back so slight I though it was a small pinhole. I kept running it but never got too low on water - it was a small leak and I kept the proper mixture on hand and kept it topped-off. Every now and then I’d get a low coolant light and I fill it up. Sometimes I noticed if using the heater after a while the heat quits and blows cold air: a sure sign of low coolant and do the same.

Then one day it blew and I limped the two miles back to the house. Pulled the radiator and had fixed. Replaces hoses and flushed the system. I never thought I overheated it because of no shutdowns or other heat related issues. However I have noticed since then if I’m driving it’ll lose an overflow reservoir of coolant every few days and get the no-heat heater bit again.

I have let it running fully serviced and warm but have seen no leaks or puddles underneath. There is no water/oil mixing signs and no steam or sweet smell coming from the tailpipe (as sometime you can see the billowing cloud and sweet smell from some car on the road). But I don’t know if there are other observable signs.

So I have:

• Radiator trouble but fixed unit
  
• Never thought it got too hot
  
• Replaces hoses
  
• Not seen obvious leaks, water-in-oil signs, or no steam clouds out of tail pipe
  
• Have not replaced thermostat or radiator cap
• And overflow tank (where I service it) runs out every few days.

Any ideas?

 

how does the heater function?? Blow hot, than cold, than hot again w a fluctuating temp gauge??

 

No temp gage, or even a 'overheat' light. As far as I know the heater just runs cold, but I will recheck it.

What does it mean hot/cold/hot? I recall reading that somewhere; purging the air in the system?

 

You got leaking head gaskets, or a warped cylinder head.

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Check that on the warped head. Might be cracked.

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I guess I missed the part where you said it blew out and where you said you dumped coolant in when the heater quit. Please tell me you waited for the engine to cool down??

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See what happens is compression leaks into the coolant system, causing it to air lock the water pump. Signs are high engine temp and cold heater. Air bubble passes then starts to circulate. Engine sucks coolant through the leak and burns it off, resulting in a low coolant light. So, your looking at pulling the heads off and a possible magna-flux job.

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Or just a new set of head gaskets w/ head bolts.

BTW, a t-stat wont produce the same results, in case you were wondering.

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I did my dads truck back in June cause it blew coolant out just as soon as it turned over. Replace the head gaskets and hasn't done it since.

 

I was kind of hoping that that a warped head or a blown gasket would have more immediate and dramatic results. Is it possible the radiator cap could be at fault, causing some kind of ‘surge’ that causes it to overflow?

 

One way to tell if its a compression leak, though sometimes it wont do it till it warm is, start it up cold and see if the upper radiator hose gets rock solid. I messed around with 5.7's to. They were notorious for blowing head gaskets and warping heads (lack of head bolts)

 

Okay, I'll try that tomorrow morning. What does that mean, malfuctioning thermostat?

 

I can tell you from experience that your heads are (99% sure) cracked. DON'T WORRY!! They all do. There is probably not a 6.2 out there that doesn't have them. It is a quirk they ALL have. It is possible that they have spread enough to leak, can't remember it has been a long time (13 years). I think it happens between #'s 1 and 2, and 5 and 6. I just didn't want you to pull the heads and freak out if you had them magnafluxed and found the cracks.

 

Sometimes it won't do anything until the engine is fully warmed up. Then if the heater get hot/cold/hot/cold, you got leaking head gaskets.