Disappearing coolant

SPANISHVETTS · 10-17-04, 04:48 AM

Last night the LOW COOANT light came. The beast has never been close to overheating and the entire cooling system was installed new last year when we did the engine swap.

I topped up the system (it took about ½ gallon) and we searched for leaks. NOTHING! Not a drop of coolant anywhere. We checked the heater core as well…DRY. The oil is perfect, no signs of any coolant in the oil. I drove about 90 miles and the light came on again and again it took about half a gallon. Even with the low coolant light on the temp never went over 190.

All I can think of now is a head gasket or cracked head but there is no excess pressure in the cooling system. Is it possible that it could be sucking coolant into a cylinder but not pushing any air back into water jackets? Thunder is running 10.5:1 compression, I would think that a gasket or a cracked head would result in pressure buildup in the cooling system. We will run a compression check next week.

I am open to all ideas.

bill81vette · 10-17-04, 06:29 AM

Do you have a pressure tester for the radiator??? pressurize the system and watch to see if it looses pressure...

If the there is a crack in the head or the gasket that goes into the cooling system then you should be seeing bubbles in the coolant while it is running...
IF by chance the crack is in the exhaust side of the head or gasket it may just be going out the tail pipe!
good luck!!
bill

jpanek · 10-17-04, 08:59 AM

My bad gasket didn't appear to pressurize the system. What finally confirmed the problem was a combustion gas detector kit from NAPA, $40. You pull air from above the surge tank (on the LT-1) through a check valve and liquid column. The liquid changes color if any CO gas is present.

Vettefan87 · 10-17-04, 09:29 PM

Are you getting a white smoke out of the exhaust? Like say if you would start it up when its colder out and have moisture in the system. Anything like this happening to your car?

Justin

bossvette · 10-17-04, 10:18 PM

I had "dissapearing coolant" on my 96 truck and it was the intake gaskets, don't know if it is your problem or not, but it drove me nuts for a while.

NevadaJim · 10-17-04, 11:51 PM

Just tracked down a similar problem on my mom's Camaro. Her husband told me that for the last week or so, his coolant has been 'disappearing'. Same symptoms as you discribed, no overheating, no signs of coolant on the ground, etc. So, during my visit this weekend I figured I check it out. After searching high and low, I started the engine and let run for while and, after about 2 minutes, I found the problem, the intake gasket had sprung a very small leak that only showed itself after the car was running for awhile. Don't know if this your problem, but if you're not seeing any smoke, it might be a place to look.

Ken · 10-18-04, 12:23 AM

Yep, intake exhibited same symptoms with me.

SPANISHVETTS · 10-22-04, 04:08 AM

Quote:

Originally Posted by Ken

Yep, intake exhibited same symptoms with me.

Ken and bossvette Where was the coolant going when the intake gasket leaked, out the exhaust or on the motor?

Here is another weird bit. Turning off the heater appeared to stop the leak. How could this be? On the 90 water always circulates through heater core so as far as the cooling system is concerned turning the heat off makes no difference.

Now the coolant has stopped disappearing. Did any of you have a symptom like this? I guess that a gasket or head could expand and contract enough to allow a leak to come and go but I have never seen it happen. I have run the crap out of it since the coolant stopped disappearing heating the motor up and letting it cool off several times and the coolant lever has not changed.

What is going on here? I am the guy who never has stupid problems. Now even with a garage full of Snap-On tools and a swarm of mechanics hovering around I have a ghost in the radiator that refuses to be exorcised.

Frankie is sending the manuals down. Maybe they will shed some light on the subject.

bossvette · 10-22-04, 07:37 AM

Mine apperently went out the exhaust, when I tore the intake off it was obvious by the condition of the gasket.

jpanek · 10-22-04, 01:24 PM

My compression test didn't show anything until plug #8 (the hardest one to get out). The color was white from burning coolant, but I never saw any white smoke because the leak was small, and the compression pressure was the same in all of them. I did have a lazy O2 sensor on that side. It took twice as long as the other one to start oscillating in closed loop.

Don't bother with the compression test - it's a PITA to remove and replace all the plugs compared to the CO test I describe above.

Is there any chance it was just an air bubble in the system from before? Hopefully maybe you just refilled it and there is no real leak since the problem hasn't reoccured. Does turning on the heater cause the leak to reappear?

Did you retighten the hose clamps since the initial install a year ago? They can work loose over time. Maybe a tiny leak onto a hot surface is just evaporating away.

Good luck, you'll get it!

Ken · 10-22-04, 03:03 PM

My intake leaked around the sealing area at the rear of the block (lifter valley) and at the heads. I saw puddles on the intake.

As for the hot water shut-off, there should be one right at the point the hoses enter the blower case under the hood. There will also be a bypass from one line (inlet to the heater core) to the other (the return line) at that same point. It's a vacuum-operated valve that closes off when you shut the heater off.

SPANISHVETTS · 10-24-04, 04:43 AM

Quote:

Originally Posted by jpanek

My bad gasket didn't appear to pressurize the system. What finally confirmed the problem was a combustion gas detector kit from NAPA, $40. You pull air from above the surge tank (on the LT-1) through a check valve and liquid column. The liquid changes color if any CO gas is present.

NAPA´s website will not accept my Euro Credit Cards.

I finally found a distributor, Midway Auto Supply, who would sell me one. It should be here Monday night. (Not 1 Auto parts distributor in Spain knew that a tool like this existed…business as usual.

)

I will wait until we know the results of this test before I start pulling things apart.

Thanks to everybody so far. I am sure that this is not over and that I shall be seeking more help, info and support.

Chetzki · 10-25-04, 01:11 PM

If it wasn't filled properly, it could have finally pushed through a vapor pocket. Also, my car has overflowed the lower reservoir several times while parked nose down on an incline.

Chetzki

SPANISHVETTS · 12-30-04, 08:31 AM

It was the intake gasket... A tube of The Right Stuff solved the problem. Thanks Ken and bossvette.

Thanks to jpanek for the tip on the exhaust gas detector.

Justardnck · 12-30-04, 01:14 PM

Well this is not the proper way to use a presure tester but if you want to make a small leak show its face pump it up to the danger zone and any small leak will become big ones... but you will find it. Just be prepared to fix it right then because you will render the car undrivable.

Some say this will cause you to blow hoses... well if a hose can't handle the danger zone then it needed replacement anyway and would have left you on the side of the road.