Disappearing coolant

[TexAndy]

Coolant temp light came on halfway up to Austin (3 hour drive). Pulled over and immediately shut the engine off. Sure enough, coolant reservoir was empty.

Only pure dumb luck I was by some oilfield service company that had a night shift person there to fill my jug. I had checked the coolant a couple of weeks prior, and it needed a quart then. Same deal a couple of weeks before that.

Had to top it off again at the parade, then again on the way home.

Probably put 3 or 4 quarts in it today, over the course of 300 miles of highway driving.

I could detect no steam or liquid coming out of the exhaust. And the oil does not appear milky, nor has it's level changed since I did the last oil change (about 500 miles ago).

NOR could I find any obvious leaks at any hoses.

The heater core has been bypassed, so it isn't leaking there.

There does appear to be some wetness on the firewall below the fuel filter box, but I assumed that was fuel, since I've been having the "start for a second, then lose prime" issue for awhile (spin-on filter base is coming). And I cannot see where the wetness would be coming from the engine.

Also, there is a film of oil on the bottom of the oil pan... but that's definitely oil.

Any ideas?

 

[Chaski]

Put a pressure tester on it and let it sit. The leak will become apparent

 

[TexAndy]

Do you mean like put a few pounds of pressure on the coolant system? Maybe a bung/fitting on the radiator?

 

[Chaski]

https://store.snapon.com/Cooling-System-Testers-Tester-Cooling-System-P772439.aspx

Something like this. There are lots of options, harbor freight all the way to Snap-on

 

[cucvrus]

Head gasket at the combustion chamber is my guess.I ran a CUCV like this for 7 years and one day steam from the exhaust. Time to fix it. This is my opinion on the cause.

 

[Al Harvey]

Pressure tester can pump 15 psi into it. Check all your clamps, sometimes the just need to be re-snugged. Also check the thermostat housing, I got one that's leaking a little there under pressure. I run the Zerek heavy duty coolant in all my diesels, it's nice because if there is a leak, it leaves a pink residue that you can see. Also one other thing to check is in the morning, is there any puddles underneath? I have had a leak before that only happens during that temperature change. Just a slight drip but over time there is a loss. But back to the original point, the pressure tester should tell you quickly where it is.

 

[Al Harvey]

https://store.snapon.com/Cooling-System-Testers-Tester-Cooling-System-P772439.aspx

Something like this. There are lots of options, harbor freight all the way to Snap-on

harbor freight one will work just fine, but yes one like that.

 

[TexAndy]

Hm. I wonder if this would work.

http://www.youtube.com/watch?v=0CfIo9niyXQ

 

[Chaski]

Hm. I wonder if this would work.

http://www.youtube.com/watch?v=0CfIo9niyXQ

Looks legitimate. I'd be careful to not over pressurize it, use a bicycle pump maybe?

 

[Al Harvey]

If you do try that method, I'd replace the radiator cap afterwards. Don't see how that could be good on the seals. It probably won't hurt it, but rather safe then sorry.

 

[TexAndy]

Took it over to a radiator shop and they stuck a pressure tester on it.

It appears to be leaking from the bottom driver's side of the radiator. Can't see it directly because of the channel/shroud on the bottom of the vehicle, but it drips coolant from there under pressure.

What do ya'll think of high-temp epoxy for radiator repairs?

 

[rsh4364]

I would just replace radiator,if its going bad in one spot its probably going bad in other spots also.

 

[Al Harvey]

If it's the original radiator, you'd be better off getting it repaired as the replacements are thinner construction. Also repair is much cheaper then replacing.

 

[cucvrus]

If it's the original radiator, you'd be better off getting it repaired as the replacements are thinner construction. Also repair is much cheaper then replacing.

This is so NOT true. The replacements that I buy are warranted for life. I have a few in plow trucks for 20 years. So I think at 30 + years his OEM radiator is thinner at places then a current after market replacement. And it won't take long to quickly surpass the cost of a replacement verses the cost of repairs. My experience is a new warranted one is a better deal if you are going to keep the truck. The replacement is about $300. I can not get a radiator recored for that price. If it were something other then a Chevy truck I would say there was something special about the original radiator. But there is not it is the same one Joe Blow bought in his civilian 2 WD 1/2 ton diesel suburban back in the day. No more no less. Just off the shelf stock GM parts. A CUCV has nothing special as far as 99.9% of the parts. Just stock GM assembly parts. That is what makes them great and affordable. Save the extra work and put a new radiator in. The time has come.

 

[Al Harvey]

I'd suggest taking the radiator and getting some quotes on prices, I've had a couple of mine repaired for less then $70.

 

[TexAndy]

I'd suggest taking the radiator and getting some quotes on prices, I've had a couple of mine repaired for less then $70.

When I get it off, if I can tell where the crack is, I might just take a crack at sealing it with some lead solder, myself.

I've got some old stained-glass lead solder (thick stuff) as well as some electronics solder. As well as some flux. And I've got a propane torch.