Im trying to stay cooler then my car!!

[Jimmy P]

OK Gentlemen around the world,

Two issues: Simple one first. Any special type of radiator cap sold / used /recommended by owners of the GT40? I have a 16lb cap with the red pressure release clip on it. Bought it at NAPA and I think its pretty good. Am I wrong? Your thoughts on better quality caps if any?

Tough issue: Why am I asking about caps? Becaue I live in the hottest place on the planet (or so it seems to me right now) and I've been chasing a cooling problem which continues. The cap is good but my good mate thinks its cheap and shouldn't be used on a car like the 40 so for peace of mind for him I said I'd ask you guys.

This is what I've done so far: I've pulled the thermostat twice tested it both times, they worked, but for the sake of eliminating that has a potential issue I put the car back together without one. So no sticking thermostat. Pressure tested the system to 16lbs and it held steady no leaks. I tightened down every screw I could get to and even eliminated the heater hoses so that should not be the cause of air in the system. Filled the system to where coolant was coming out of the upper rad. bleed valve and the bleed valve on top of the engine. BTW its a CAV pre 100 car should you need that. We removed a wee bit of solder found inside the rad cap neck which was not allowing the cap to seat correctly and then garage tested the car. The car got up to temp and then got hot the fans came on and water began coming out of the expansion overflow tank. We shut the car down and considered the fluid was excess from my over fill of he system. We also thought it got hot because there was no air flowing through the rad. except for the fans.

I waited for a cooler night and after a heavy rain got that last night to road test the system. Got about 3 miles saw the temp starting to rise and rise so I manually turned the fans on but still rising (120+celcius) and pulled over. I had water coming from the left side pontoon area where the lower rad hose runs back to the engine and coolent from the lower expansion tank, and a very small amount of steam from the expansion tank attached to the firewall. Heres a good piece of info that I think is most telling. My cars cooling system runs counter clockwise and as such the top radiator pipe should be bloody hot while the lower one cool. I felt the top pipe and it was luke warm at best. The lower cool to the touch. The expansion tank of course boiling.

I hate to think this but its got to be the water pump.....but its literally new. What else could it be? Your thoughts please and thanks.

[Eric]

Jimmy

Regarding the radiator cap, a 16 lb cap is a 16 lb cap. Doesn't matter where you bought it, if it tests to hold 16 psi, then it's fine. When you pressure-tested the system, did you pressure-test the cap, too?

A bad head gasket will cause an over-temperature condition, but your pressure test would have shown pressure leakage. On some engines, installing a head gasket backward will block off certain coolant passages, which causes an over-temperature condition.

If the cap wasn't holding pressure, you'd be getting boil-over at a lower temperature, in which case it might not be a true over-temperature situation. But, you said your temperature gauge showed temperature rising, so it would seem the boil-over is occuring due to an actual over-temperature condition.

I'm not exactly sure what you meant by your cooling system running counterclockwise. Do you mean your pump runs counterclockwise? If so, my first question is to ensure the pump is designed to run in that direction (I'm sure you've already verified this).

I agree with you regarding the temperature of the radiator hoses. If you are seeing boil-over, at least one of the hoses should be very hot (an probably both). If you can grab on to the hose for more than a few seconds, then you have some sort of issue preventing flow through the hose. That could be a bad water pump (or reversed), air pocket in a coolant passage someplace, bad thermostat, collapsed hose, clogged radiator, etc.

I guess I really haven't given you any solutions. I'm just trying to think this through with you.

Eric

[Randy V]

Let's talk about the events leading up to this...

What engine is this?

Was it just fine for a long period of time and then just suddenly it started misbehaving?