1995 Z28 Disappearing Coolant... - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

7Charlie · 07-07-2009, 09:29 PM

Alright guys, I've searched the forums on here, and can't find anything that sounds related.

I've got a 95 Z28, bone stock, 109,000 miles on it. From about 100k to 107k, the low coolant light had been occasionally coming on. I ended up replacing the radiator, H20 pump, heater core, thermostat, hoses, etc.

Over the past 2k, I've had to add about 3 gallon of coolant. Here's the kickers that make no sense to me...

A) I have no visible leaks under the vehicle, ever.
B) Once the engine is warm, I get no steam or water vapor out of the tailpipe.
C) No coolant contamination of the motor oil.
D) No oil contamination of the coolant.
E) Just recently pulled the valve covers to quiet down a loose rocker - the tops of both heads were spotless.
F) No coolant contamination of the auto trans fluid.

Before I start to spend mucho bucks... any advice? I'd think with a cracked block / head / blown gasket, I'd see some contamination somewhere.

Anybody ever had anything like this???

Thanks in advance for your responses.

//7C

**CKJ** · 07-07-2009, 09:36 PM

The one thing you could do but its a royal pain is to pull every plug in the motor to see one is being "steam cleaned"

alpine247 · 07-07-2009, 09:40 PM

had the same problem and came to find out it was the radiator cap was bad.

so give that a try ...

blk99ek · 07-07-2009, 10:12 PM

I would get a leak down tester and pump the system up and wait and see if you can't see anything. Look under the throttle body on the passanger side and see if their is any coolant down their

shoebox · 07-07-2009, 10:43 PM

Check the overflow pipe that runs under the battery to the remote reservoir. It can leak very slowly to where you will never see any coolant hit the ground. You will have to remove the battery.

96RedZ28 · 07-07-2009, 10:46 PM

I just got done with that problem today... Wondered where all my coolant was going when it wasnt on the ground... It got hot and turned into steam, found out radiator cap was bad.

7Charlie · 07-10-2009, 11:04 PM

Thanks for all the advice guys - found the following.

Got a leakdown tester. Tested the radiator cap - it would pop off around 16-17 psi, but would then quickly leak down to about 7-8 psi. From what I can understand, this indicated the cap is bad, correct? My understanding is that the cap should "pop" in the 17-18 range and then hold that pressure, right?

Put the tester on the radiator itself - Pumped it up to 18 psi. After about 2 minutes, I would say that I was down to about 17.75... very little to no loss. Is this enough to even worry about? Or should I just get a high quality "stop-leak" additive, run it for a few days, and then test again?

Thanks for your help in advance.

**CKJ** · 07-10-2009, 11:08 PM

Leave the tester on for much more than 2 minutes. I usually put them on and walk away for 15-20 minutes.

I've personally never tested a cap for I don't have that adapter for my pressure check setup. If in question, just buy a new one

Can't run no more than 5-7 bucks just a guess.

7Charlie · 07-10-2009, 11:12 PM

In reference to the tester - will do tomorrow.

Should I see any leak down in 20 minutes? Is there an "acceptable" figure?

Thanks.

**CKJ** · 07-10-2009, 11:21 PM

You shouldn't have any if you want to get 100% technical. But I would imagine if it sticks to that 1/4 PSI then you shouldn't have any real problems. I think 1/2 psi would bug me enough to where i'd start searching.

Dennis93TA · 07-11-2009, 09:01 PM

I have a question, Do you hear any "bubbling" in the radiator after you shut the car down after the car is hot?

Reason I ask is not many people could tell me why one of my cars would do this, it would lose coolant but I could not locate the leak. After buying a coolant test I found my headgasket was bad. I had no cross contamination of any fluids and nothing out the tail pipe. Just bubbles in the radiator. It's a wierd situation where the pistons will push air(exhaust) into the coolant passages but not the other way around.

Just a thought.

7Charlie · 07-11-2009, 09:16 PM

I'll check on the bubbling - I can't say that I have heard it, but I don't know if I have paid enough attention after a hot shutdown.

I redid the leakdown test, found about 1.5 psi loss after 20 minutes.

I'm going to try a combustion gas leak test on the cooling system next, just to verify that I'm getting contamination.

Thanks for the heads up. Next time I get her warm, I'll be sure to listen to the cooling system for a while.

**CKJ** · 07-11-2009, 11:28 PM

Quote:

Originally Posted by Dennis93TA

I have a question, Do you hear any "bubbling" in the radiator after you shut the car down after the car is hot?

Reason I ask is not many people could tell me why one of my cars would do this, it would lose coolant but I could not locate the leak. After buying a coolant test I found my headgasket was bad. I had no cross contamination of any fluids and nothing out the tail pipe. Just bubbles in the radiator. It's a wierd situation where the pistons will push air(exhaust) into the coolant passages but not the other way around.

Just a thought.

Hell Dennis, if thats the case almost every one of my cars would have a bad gasket. I know my 92 Cadi does it

I don't know...i'm just...lost, forgive me.

Dennis93TA · 07-13-2009, 11:00 AM

There is a tester they sell, I forget the name of it, you take off the radiator cap and push this thing into the radiator, fill it up with the special fluid and use the hand pump. If there is any exhaust gases in the coolant it will turn the special fluid a diff color, which either means you have a bad head gasket or a cracked head. I have the tester somewhere, I may have to dig it out and get the name of it, I think it is simply call a "Block Tester"

7Charlie · 07-13-2009, 11:11 AM

Yeah, that's next on the list. I've currently got an issue with my rocker nuts backing off, so I'm trying to get through 1 issue at a time. Thanks though.