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I am on the verge of SNAPPING- coolant loss issues

Can Can

Can Can

Pusher Man
Joined
Feb 17, 2000
Posts
16,432
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2,735
Location
Cochrane, Alberta, Canada
The truck- 83 6.2 C10

The background- A couple of months ago my "low coolant light" started flashing every so often. I kept an eye on the overflow tank and the coolant level was always right on. I just figured that the sensor was playing games with me(it has done it from time to time in the past). A couple weeks later I noticed a very small leak coming from somewhere near the upper driver's side of the block. After a lot of checking I was still unable to determine the location of the leak. I figured it wasn't too bad because the coolant in the overflow tank was STILL sitting at the proper level.

Background Part 2- After a couple of weeks I decided that I had better check the coolant level in the rad. I'm very embarassed to admit that the rad was down about a 1/2 gallon!!!!!! The leak hadn't really gotten any worse so I said "[darn] it" and added a can of stop leak to the rad. I did notice that the coolant level rose quite a bit as the engine warmed up. Within 100 miles it appeared that the leak had stopped. /forums/images/graemlins/thumb.gif

The problem- Last night the "low coolant" light came on again. This morning I checked the rad and it was down about a half gallon AGAIN!!!! /forums/images/graemlins/angryfire.gif

The leak has not returned which leads me to believe that the coolant is burning off internally, ALTHOUGH THERE ARE NO TELLTALE SIGNS OF COOLANT GETTING INTO EITHER THE CYLINDERS OR THE OIL. What the [darn] is going on???!!!!! /forums/images/graemlins/dunno.gif

I have 2 questions-

1. Generally if your coolant level in the rad gets a little low, the rad will "sip" from the overflow tank. Why is my truck not doing this?

2. How low will the coolant sit in a rad when the engine is cold in, let's say, a SBC 400(that's the closest to a 6.2)? Is it normal for the coolant to be that low in the rad when a bigger motor is cold? With my 305, the coolant is always near the top of the rad when cold.......

Sorry for the long winded post, but I've gotta get a handle on this issue before I lose my cool(no pun intended) and drive the ol' diesel off a cliff......
 
Hey Bro!

WRT your coolant issues, Check and make sure the hose going from the rad to the overflow tank isn't blocked with crap. That could explain why the overflow tank level isn't changing. My dad's 92 K5 had this problem.

Also, check for moisture around your "weep hole" on the underside of the water pump. If it's got a lot of miles on it, it's a trouble spot. Both my 84 & 87 K5's had this problem. My 87 leaks where the intake meets the block, above the timing chain cover. waiting for the warm weather to fix that.

Did you shine a light on the backside of the rad and look for wet spots? sometimes the forward motion of the truck carries the leaked coolant backwards all over the block. Had that happen w/ my Camaro.

If your oil isn't looking like a milkshake, I'd say the head gaskets are ok, but then I realize that diesels have a higher cylinder pressure so maybe the gaskets are bad and the coolant is being vaporized, rather than remaining a liquid and polluting your oil. Just a thought.

Tom /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif
 
ON my k5 every month or two i would wonder why my coolant level was down and how it could have possibly leaked that much out....
Well when i ended up having to take the heads off the engine and found a nice crack in one of the heads, that might explain why i was losing coolant.. probably slowly vaporizing and never seeing it.
/forums/images/graemlins/thinking.gif Since i put different heads on my 350, i haven't seen any coolant loss like before.
 
Thanks, Tom.

My water pump is good. The intake isn't an issue because no coolant passes through the intake on a 6.2. I'll take a close look at the backside of the rad but I'm pretty sure the problem isn't there. There's absolutely no sign of coolant spray anywhere under the hood..... /forums/images/graemlins/dunno.gif

Thanks for the reply, brother.
 
[ QUOTE ]
Well when i ended up having to take the heads off the engine and found a nice crack in one of the heads, that might explain why i was losing coolant.. probably slowly vaporizing and never seeing it.

[/ QUOTE ]

ARRRRGH!!!!!!!! I was afraid someone was gonna say that.... /forums/images/graemlins/angryfire.gif

Can a cracked head leak outward? And how long can you run a motor with a cracked head? How do you test for a cracked head without dismantling the motor?

It looks like I may have to delay spending cash on a lift kit for the K5 until I figure out if I gotta rebuild the 6.2. [darn]!!!!! /forums/images/graemlins/angryfire.gif
 
Don't mean to scare ya there man.. Just figured i'd tell ya what it happened to be in my case...
You can get a radiator or coolant pressure tester thingy...
Its a radiator cap that you can pressureize with a handheld pump... You pump it up to about 15 or 20 psi and watch the gauge to see if it is leaking out pressure... Then with the engine not running you can hopefully hear where it is leaking if it is significant.
 
Sister had an '88 beretta. Car would lose fluid. Never saw it leak. Came over to the house one day, and she parked the car. For some reason we came back out to the car after about 15 minutes. Coolant on the ground.

Long story short, cause? Stop leak of some kind (although debris could also be a culprit) in the overflow tank acted as a one way valve. As water was pushed into the tank with pressure (since it goes in on the bottom) it would force its way through the crud. But once the pressure was gone, the junk would actually plug up the line, and the fluid couldn't get back to the radiator. So the overflow would continue to suck up fluid, but only leak it once the engine was turned off and temperature increased the pressure in the cooling system.

Odd situation, never heard of it happening to anyone since, but once the overflow tank was cleaned, the problem never returned.
 
The coolant overflow bottle relies on the expansion and contraction of the coolant, and a tightly sealed cooling system. As the engine heats up, the coolant expands. A pressure relief valve in the radiator allows the excess to go through the overflow hose and into the overflow bottle. As the engine cools down, the coolant contracts. That tiny silver disc on the inside of the radiator cap acts as a one-way valve and as a vacuum is created in the cooling system by the contracting coolant it draws coolant back from the overflow bottle. A leak anywhere in the cooling system can let air get sucked back into the radiator, instead of coolant.

BTW, I never rely on the level in the bottle to tell me how the radiator is doing. I pull the cap and look down inside the radiator. A well sealed, functional system should always be full right to the top of the neck of the radiator. /forums/images/graemlins/thumb.gif
 
I'm not familiar with deisels. you stated that no lines go to the manifold. I guess the heater hoses go to the radiator and the water pump then? I had this weird leek like your's. Turned out one of the heater hoses was splitting between the 2 layers. the inside layer had a leak and ran down the hose between the layer and burned off on the manifold. You couldn't see it happening, but new hoses fixed the problem and you could see the old hose had seperated once it was off.

Then again maybe your head is cracked. j/k
 
[ QUOTE ]
Turned out one of the heater hoses was splitting between the 2 layers. the inside layer had a leak and ran down the hose between the layer and burned off on the manifold. You couldn't see it happening, but new hoses fixed the problem and you could see the old hose had seperated once it was off.

[/ QUOTE ]

Wow!!! That's a wierd one!!! /forums/images/graemlins/shocked.gif I've never heard of that before.

I have another post going about the same issue, Rob. See if it gives you any more ideas....... /forums/images/graemlins/thinking.gif

PS. How's the little one doing?
 
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