Well i posted a topic about overheating a while back and im sorta having the same issue again. Every so often it will loose about a gallon of antifreeze and suck in a bunch of air. There is no water in the oil i never see any on the ground and it only seems to do it the day after i drive it hard. Now i know the logical answer would be to stop driving it rough but thats just not gonna happen lol. whenever it happens i take the purge cap off after the water pump going to the heater core then i refill the radiator and make sure i get all the air out and then its fine. Im just at a loss and have no idea what else to do. also Whenever its going to happen i always lose heat in the car.Btw the pass. floor is not wet either so i know its not the heater core blowing it out. Any ideas? i know these cars are notorious for overheating so im sure someone has ran into this problem or something similar.
Thanks
Trevor
Its a 94 v6

 

You need to fill up your coolant and do a pressure test. You can borrow the Pressure tester from Autozone. You will just need to leave a deposit. Pump your system up and see where the coolant is going. If you keep dropping pressure and you do not see any Coolant puddles start it up if you get a bunch of steam its a blown head gasket.

 

Check the orings that are on the heater hose connections. The coolant will leak onto the motor and burn off without dripping on the gound. We replaced head gaskets, new rad hoses, cap, etc and we were still losing about a gallon of coolant a week. I just happened to move one of the heater hoses while car was still hot (normal temp) and seen the water start running out of the connection. Replaced the Orings and haven't added a drop since.

 

Sounds like the radi cap is not holding back 15 psi. Yeah, I am sure they have a radiator cap tester. I usually pump to the red 18 psi and hear it blow off and hold 15 is more you have that problem.

You said nothing is in the oil. That says no head gasket leak. No coolant on the floor all this time. So, count the radiator out. No leaks or puddles you can see on the intake manifold or you would say steam is coming out the exhaust. No puddle on the garage floor. No coolant smell at the heater core. Maybe vaporization out the recovery tank is the loss?

My guess is a radiator cap short of pressurizing the block/radiator for 10 minutes @18psi, see if it drops and then look under the car for the drop. Then look straight up from there.

 

No coolant in the oil means the headgasket is not blown between the oil return in the head and the coolant system. It very uncommen for a head gasket to blow there. Most of the time when a head gasket blows its the the ring around a the cyclinder that blows out into a coolant passage. This will not result in coolant in the oil. Most of the time when coolant gets into the oil the motor will need a complete rebuild.

The pressure tester comes with a cap tester, Funny part is I looked up his last post he made about this problem and I told him what to do in that post also. I even included the part about the checking that cap. As a GM and ASE certifed master tech who has repaired 100's of head gaskets I can say if he takes that car to any decent mechanic that mechanic will reach for a pressure tester. That is unless he has a exhaust analyzer in which case he could just check for hydrocarbon in the radiator. That would prove the headgasket but he would still want to pressure test the system to check for any additional external leaks.

 

As Gorn said, the easiest way to find a leak is with the pressure tester. If you get to know your AutoZone as well as I do, you can drive up and use their tools without even paying the deposit, LOL.

Since you're only losing coolant when you drive it hard, I would suspect the rad cap. It sounds like that's not holding high enough pressure. If you're driving fast enough (or fans on high speed), then coolant lost from there will be misted back towards the engine, where it will evaporate so fast you don't ever see a drip.

Another place that's notorious for dripping slowly and then gushing when you push it is the heater bypass pipe under the TB. Again, in this case the coolant drips straight onto the engine block and evaporates right away.

Get a pressure tester and look at those two places. Even if you do find one of those places leaking, check everything else too while you've got the tool, LOL. Better safe than sorry.

 

Gorn has told me a half a dozen times to go to autozone and get the pressure tester i just keep putting it off. Why is it only doing it randomly? also if it was a head gasket would'nt it leak out all the time not just randomly. It doesnt only do it whenever i drive hard it does it randomly like it has a mind of its own. If it turns out to be the head gasket what kind of trouble am i getting myself in there, how much time and beer should i allow for that. i know replacing the headgasket in my old jeep only took a few hours but it was a straight 6 with everything right on top

 

The pressure tester will help find where the leak is regardless of what it is. I used the headgasket only as the worse case. Try the tester and see where the leaks are before you start worrying how to do a head gasket. Maybe it just a water pump or the Cap.

Testing in autozones parking lot is not a real good idea because the motor is going to be hot. You don't want to try these tests on a hot motor.

 

Do what Gorn says. If the head gasket is leaking, or at least in our case, you have other issues besides just loosing water, like engine misfiring, getting hot, white smioke out the exhaust and then bogging down and surging.

 

osduck, The blown headgasket effecting the way the car runs in a sign of a real advanced blown gasket. When they first start the first thing you will see is pressure in the coolant system even before the car is hot. This is when there is a very minor leak, it may allow only a small amount of coolant into the cyclinder maybe a few drops during the intake stroke. I have even seen it where there was no sign of coolant in the cyclinder just compressed air pushing into the coolant system under extream pressure. Also if the head gasket is blown toward the top of the motor the motor is less likely to draw coolant in because the coolant level is almost alway low.

I was working on a car one time and I suspected a head gasket. I check it with a 4 gas analyzer and I found hydrocarbons in the Radiator. Hydrocarbons come from the burning of gas. So it has a leak, right. The guy did not believe me so he took it to another mechanic. That mechanic did a pressure test and could not find anything wrong. I got a nasty letter sent to the dealership saying we where trying to rip him off. 8 weeks later he was back. His mechanic now says he needs a head gasket. Even then the only issue he had was a slight idle issue but the car was starting to lose coolant and would no longer pass the pressure test. The point to the story is that unless a car overheats or is run super hard head gasket failure happens over time. You get to the point coolant is fouling a plug or you can see a pile of steam coming from the tailpipe your pretty far down the blown head gasket road.

Once you have a tester hook it up and start yur car cold. Noramlly it will take 3 to 5 minutes to start to build pressure. It can take 10-20 minutes to get to 15 PSI. If you start building pressure real quick, like a minute, you have an issue. I have seen cars that ran fine push 10 PSI into the coolant system in less then 30 seconds.