ryanbeezle

1996 ES300

I've started some other threads about issues related to my overheating situation, but I think this is worthy of a new one.

Background info:

I've had overheating for months now. Replaced t-stat, rad cap, upper hose and hydraulic fan motor. They've all helped to some degree but I never nailed the root problem. When I turn the engine off, there's air coming out of the radiator cap neck into the reservoir causing bubbles in the reservoir. I'm not sure if it's supposed to blow air, but I assume not.

Whenever I park and cut the engine off, I immediately notice a puddle under the overflow reservoir area, but it doesn't continue noticeably leaking afterwards. After some hours, I notice fluid around the passenger side tire. The fluid may be leaking down the tire now that I think about it. The aforementioned bubbling isn't enough to force all the fluid out of the cap and the cap always remains securely attached.

My real question is: What would make the overflow reservoir leak when the car isn't even running? Every morning it's empty, or after a couple hours sitting.

KawiLex

Take you car to a local shop and have them test the coolant system. They can pressure check it and find the leak quickly, otherwise you will need to do some troubleshooting yourself. I'd pay to have it done if you haven't figured it out by now. Likely a bad reservoir or connection there.

LeX2K

You need to go back and do basic troubleshooting steps. Coolant puking out the reservoir is a sign of a bad rad cap (did you use an OEM part here?) or excessive pressure due to overheating OR exhaust gasses being forced into the cooling system.

The check valve on the reservoir cap installed backwards can also cause coolant to leak out but it won't cause the bubbling of coolant like you're getting. As the engine warms up coolant expands and is pushed into the reservoir that's why it is there. At a certain temperature the rad cap no longer allows this and the system pressurizes. From that point as long as the engine is at operating temperature coolant should never be pushed out the cap.

ryanbeezle

Thanks for the responses. Lexus2000, your comments have helped tremendously with my understanding of the cooling system.

The reservoir had a hole in it near the top and a large crack on the side. One step closer to solving this overheating problem. Now I can look for REAL leaks.

KawiLex

Real leaks? I only diagnose the fake ones, so you're outta luck there.

ES300NZ

Hey, that's a classic symptom of combustion mixing with the water system. The usual cause is a cracked head or a blown head gasket.

sorry, .. that engine's probably stuffed mate.

ES300NZ

thats because the water in the plastic container has been superheated by the combustion gases mixing with it.

I used to buy $50 -100 cars with friends as a kid. We'd trash them senseless for a week or two, take them out to street races, race them, lose of course, and generally have a blast with them. So, I can with some certainty that if combustion has been mixing with the water system then overheating issues like this are usually the death of a car.

ES300NZ

excessive pressure (excessive expansion into steam): my money is on that. {I bet the caps operating fine, but it's so hard to diagnose stuff like this without being over the car and seeing all the little things that tell you so much about what's happening.

INNOUTFAN

Head gasket failure will cause combustion gases to pressurize and superheat the coolant - usually you will blow into the overflow tank and it won't necessarily happen right a way. How does your oil look? Chocolate milk looking means you are mixing coolant/oil - stop driving immediately before you spin your bearings.
Intake manifold gasket failure can cause the engine to overheat, and you will notice a loss of coolant, but it won't necessarily pressurize the entire cooling system. The coolant will become part of combustion and you might get a sweet smell at the tail pipe.

ES300NZ

A+ reply. couldn't have said it better myself