OK, so i got the coolant pressure test system, and hooked it up to the car,
Pumped it up to 16psi, and could not find any leaks. I hooked it up to the radiator cap (rated 17) and the cap would lose pressure around 14.
Replaced it with a new cap, burped the radiator, and it worked fine for 150 miles. No low coolant lights, good temps all around, no leaking.

Then suddenly the other day, low coolant light comes on; on the freeway, and I get home... the coolant is very, very low. No signs of leakage.
It's almost like it works fine for a week, then "vomits" all the coolant up while driving.

Now it seems to me that if I've got a coolant leak, it should /always leak.

The water pump is dry as a bone, no moisture around any of the hoses, and the "oil cooler" is also dry.

Any more ideas on this?

 

Maybe a head gasket is failing? Any smoke coming out of exaust?

 

No smoke on start up.

 

you might not get smoke on startup... it more than likely would be a cloud whilst driving down the highway.... and I would expect you would see it.

now... check the radiator itself. you may have a bad seal on the side tanks. it is ok for a while, then pukes after it gets warm.

 

I tested the pressure with the car hot and cold, wouldn't it puke the coolant out all the time when it's hot?

The part which confuses me is that it works perfectly fine for a week, dumps the coolant, then works fine for another week.



[Modified by Kale, 12:32 PM 9/2/2002]

 

Had the same thing happen on a Dodge Daytona IROC. Took me awhile to see the seam was split at the side tank.

 

Check the car when it is hot by pulling a spark plug and turning the car over. Check each plug and coolant will shoot out of the plug hole if it is leaking thru the head into the piston chamber.

You may have already tried this.

 

Kale, if you have an internal head gasket leak, you should experience the following conditions:
1. Loss of vacuum. The coolant will not flow in reverse from the plastic bottle to your expansion tank, as the engine cools. Is your bottle full? Is your expansion tank empty?
2. Operating temperature will be very high, as the engine could be pumping exhaust gasses
into the coolant system.

Your process of elimination is commendable. Locating a leak should not be this difficult. Try this, if you haven't already: after parking your vette after operation, place newspapers under the whole front end to see if any drips are evident, unless your garage floor will show the same results.

You are correct about a leak being present as long as there is pressure on the coolant. Loss of fluid over a short period (150 miles) indicates an opening somewhere, destroying your closed system.

As you know, when you applied test pressure to your radiator, you were only testing that portion of the system, and not the engine.

It is recommended that any temporary measures such as, stop-leak, etc., NOT be poured into the radiatior.

 

Kale, one more suggestion relating to a possible head gasket leak: after each trip in the vette, let the engine cool, and then loosen the expansion tank cap. If you have a gasket leak, internal pressure will be increased, and you will hear air escaping from the expansion tank. And, as I mentioned previously, the tank will be low on coolant, due to the internal pressure preventing a vacuum from forming, and the overflow bottle will be full. As you are aware, after cooling, your expansion tank should be full after syphoning coolant back from the overflow bottle, confirming that your system is "closed".

 

So when the car is cold, lets say, the next morning, the overflow tank should be low/empty?

 

Let's make sure we have our "tanks" identified correctly. The EXPANSION TANK is the metal tank mounted high near the fire wall, passenger side; and the OVERFLOW BOTTLE is the plastic container located in front of the right wheel well. When the engine is cold, the EXPANSION TANK should be FULL, and the OVERFLOW BOTTLE should be at the FULL "level" (this level is marked on the bottle about mid-way on the bottle). We all know coolant expands when heated. That is why there is a recovery, or OVERFLOW BOTTLE. In the "old day", car radiators just had an overflow tube that flowed onto the ground. With a proper radiatior cap, a vacuum is formed when the engine cools, syphoning back the coolant that it expelled during operation. If you have a head gasket leak, you will not have a "closed system, which prevents a vacuum from forming. Consequently, coolant will not return to the expansion tank, and the overflow bottle will keep accumulating coolant.

INSPECT YOUR RADIATOR CAP AND MAKE SURE IT IS FOR A "CLOSED SYSTEM". AN INCORRECT CAP WILL NOT ALLOW COOLANT TO FLOW BACK TO THE EXPANSION TANK.

 

Intake gasket. :cheers:

 

Kale, I used the term "INSPECT THE RADIATOR CAP....... "in my prior response. It should be corrected to read: INSPECT THE EXPANSION TANK CAP.....

 

Kale, we have one tank, the plastic tank in front of the right felder well.

Check to see if the level in that tank is moving up/down according to the marks on it's dip stick.

I've had the "low coolant" light intermittently for some time now and finally pulled the rubber hose and tank. I found that the hose was split under the top clamp. This would let coolant flow into the plastic tank but would break vacuum and not pull it back up. I just cut the end off the hose and reattached it; I'll let you know how it behaves.

Check your coolant hose to that thank to be sure it's air tight at both ends and no splt in the plastic pickup at the bottom of the tank; then burp the system and check the coolant level in the tank to see if it's moving up/down properly.

Lets hope the problem is in that area.

 

I dont' think I have one... or If I do, I can't find it.

I replaced the line to the overflow tank a few times already.. even sealed it with gasket maker.

 

Hello Kale,
My 1990 would loose coolant in similar fashion. I didn't do the pressure test in my case but the cause of the leak was an aluminum hose on the passenger side of the engine bay. The hose was allowed to rub against the frame because it's bracket worked it's way loose. The hose (pipe) made contact with the frame causing a hole in the hose.

Take a good look on the passenger side of the car between the fuel filter and front wheel and trace along the frame. Hopefully this helps you.

 

sorry to hear! i figure you have enough help, so i'll crack a joke,
"how about driving the car every other week.?" :D :jester

hope you get this resolved, the guys are all on the right track! :cheers:

 

KALE, when 65ZO1 responded to you, he indicated that you only have one tank. You have a radiator and an overflow bottle. That being true, there is an "opening" somewhere in that system. I really don't think you have an exhaust head gasket leak. That kind of leak causes immediate problems, such as, overheating after a few minutes of operation. The engine, acting as an air pump, displaces your coolant and heats your water rapidly. A simple test to locate your problem is to fill your radiator completely, and fill your overflow bottle to the "full cold" mark (about mid-way on the bottle). Drive your car so that you reach operating temperature. Let it cool, and then remove the radiator cap. A working "closed system" will show the radiator full and the bottle at the "full cold" mark, where it started. An "open system" will result in a low water level in the radiator and a high level in the overflow bottle. This is caused by a leak in the system, preventing a vacuum to form, and not allowing coolant to return to the radiator during the cool down.
It doesn't take much of a hole to prevent a vacuum. If you are confident that the tube from the radiator to the bottle is solid and clamped, and the tube to the bottle end is solid and tight, you have resolved one piece of the puzzle. I mentioned the radiator cap. It must be a closed system cap, as the spring loaded mechanism retracts, allowing a vacuum to form, and the coolant to return to the radiator. Check your return hose INSIDE the bottle, to make sure it is connected to the interior fitting that connects to the radiator tube. That hose can come loose, breaking the vacuum. Then, bring the vette to operating temp, and using a drop-light, or flash light, carefully scan the entire coolant system for any sign of moisture. I have always found it beneficial to have a "cool one" while thinking about your dilemna. And lastly, with the engine cold, slowly LOOSEN the radiator cap, and listen for air escaping. That would signal an exhaust gasket leak in the engine. Let's hope you don't hear any air escaping.
:cheers:

 

Hey! guywade, your solution to Kale's coolant problem belongs in TECH TIPS! :cheers: :yesnod: :lol: :cheers:

 

That's explained well enough even /i/ can follow it . :lol:

I'll give it a shot, thanks :)