I don't normally post in this section, but we have an FC problem so I figured this is the place to go.

The car is an '87 with silicone hoses, stock rad, FCD, and other non-pertinent mods. If driven at normal speeds, below 3000RPM, it will begin to overheat and blow coolant from the overflow tank. However, if driven harder, and the RPMs are kept higher, it doesn't overheat. No coolant leaks, and the water pump is in unknown condition.

I performed the coolant seal test today per the FAQ, and it doesn't push out large volumes of water, rather it seems to slowly build some pressure, possibly push a little coolant, and make a lot of bubbles.

Would this still be considered a coolant seal failure? I just want to be sure before we pull the motor and take it apart.

Any help is appreciated

Thanks,
Wyatt

 

Check exhaust for white sweet smelling smoke,
If so:
Check oil for water.
Check compression.

If good:
Change the water pump and thermostat.

Other than that you might have something clogging the radiator.

My guess is the water pump impeller is corroded to the point it's just cavitating coolant.

 

How is your stock fan clutch? If it is too weak, it will not flow enough air at low speeds but it'll be enough at high speeds.

How many belts are you running on the water pump? A single belt may be slipping.

Do you know if it is an OEM thermostat? Other brands have caused problems.

Bubbles during the champagne test are difficult to judge because the engine is vibrating and splashing fluid. Did you use a lisle funnel, a plastic bottle or just pop off the cap?

 

Rotor demon might be right follow his suggestions though. But to me it sounds like the coolant seals are done.trust me I've had tons of you motors go out due to coolant seals and everything you've described sounds like coolant seals to me.good luck

 

Just took the cap off, didn't think to use a funnel. Forgot to mention, I was told by the previous owner it has NO thermostat in it. I'm sure it isn't a fan or belt issue.

Thanks for the input.

 

You need a thermostat in it. Go get one and drill a small weep hole in the side of it if it doesn't have one.

 

Update, put a thermostat from a FB we had sitting around and it made the problem worse.

Its weird though, the gauge never got really hot, maybe a smidge over normal, but it started pushing steam out of the overflow. The really weird part is the upper rad hose was hot, as it should be, but the bottom rad hose was barely warm.

 

Can you even use a FB thermostat? Was it a gsl-se? I dont know, just get the right one...oem.

 

I checked on that and both cars have the same part #'s for the thermostat.

 

Update: we put on a new water pump, and it was deeper and had bigger impellers, and we got a smaller belt that actually fit properly. It totally changed the way the car behave. Even on just a test drive with no fan shroud, it never even thought about overheating. We also tested the radiator and it isn't clogged. Also, the FB thermostat worked fine.

None the less, the car still pushed water out of the overflow. So, at this point I'm pretty sure that it's coolant seals. However, we will try a known good rad on it to make sure that even though it isn't clogged, there isn't restriction causing the backup of water into the overflow.

 

If its not overheating but still shooting coolant into the overflow bottle, wouldn't that be the radiator cap? Old caps let water out at lower pressures than they need to.

It's cheap enough that you can afford to try it ether way.

 

Hmm, it claims to be 13lbs I think? It's brand new though

 

Never mind then.

Generally speaking, if you think something is wrong with a car, and have evidence, it often is.

If no smoke is coming out the exhaust at all, then the coolant seals themselves are probably fine. A clog somewhere might cause it to overflow.

BTW, did you inspect the cooling fan?

The primary diffence between low speed and high speed cooling is that the fan only spins at low speeds.

Get the car hot, then shut it off and make sure it's hard to spin. If it freewheels, you have a bad fan clutch.

Flushing and inspecting the coolant would be a good idea.

 

The smoke from the blown oil seal in the turbo makes it almost impossible to see any other smoke. It has to be coolant seals, thanks Valkyrie