Hot coolant going out from the radiator

[joseG]

Hi all,

I have a problem of coolant going off the radiator cap for a little while now

It happens when the car is at running temperature. (4.2 2+2 1969)

There is no overheating (at least the gauge stays were it should) and the fans work as well so even with the 35 degrees we had in Paris lately the car does not seem overheat.

I've changed the caps (both on the radiator (normal cap) and the radiator header tank (7lb cap) )

I've changed the all the rubber pipes (kit from SCparts)

I removed the heater box and short circuited it by putting 2 rubber pipes to eliminate a pb ... but the issue it still there.

As soon as the engine to up to temperature I can see water coolant coming out from the radiator

Anyone has a tip or a suggestion ?

Thanks in advance !

[mgcjag]

Hi Jose.....what type of cap do you have on the radiator..you say normal....does it have a spring or no spring and have you checked ghe thermostat

[chrisfell]

A '69 car should have an expansion tank with the pressure cap on the bulkhead and NO pressure cap on the radiator. What have you got?

Sorry, re-read the original post.

[politeperson]

Sorry to state the obvious but if you can see water coming out of the radiator, you need a new radiator.

Boston Motor Cool rebuilt mine with a new core for £230.

There is a cap on the radiator, it is not a pressure cap, just a seal. Well I have one on my 69' and a pressure cap on the expansion bottle. Works a treat.

[christopher storey]

I am puzzled by this. From where do you see water coming out ? If it is coming from some part of the metal, then clearly you have a leak . Or do you mean that you have transparent pipes between the radiator and the bulkhead tank ? If that is the case, then seeing a coolant flow to the tank is absolutely normal

[joseG]

Thanks to all,

I will try to answer to everyone at once -)

1- The water is going out of the radiator CAP. The cap has no spring and I "doubled" the rubber on this cap just to be sure that is closes well and fair but still the water gets out from the cap

2- The fans are working so I concluded that the thermostat is working ? Maybe I am wrong?

3- The radiator has no leak, its when the car is at temperature that the pressure seems to build up so much that the coolant needs to find a way out and so goes out from the cap

Thanks again in advance for your wise remarks and advices

JOSE

[mgcjag]

Hi Jose......on the side by the radiator fill cap should be a small tube going to the expansion tank .....do you have this and is it blocked? You should be able to blow through it all the way to the expansion tank.. any expanding water from the rad should go up this tube to the expansion tank, if the pressure gets to high the relief cap on this tank opens and alows water out through the small pipe....the fans work from the otter switch, an electrical switch on the front top of the radiator....the thermostat is in a housing on the front of the inlet manifold. the top large hose from the rad connects to it....the thermostat stays closed till the engine warms up and then allows full flow through the radiator..on top of this is a temperatute transmiter for the temp gauge

[drcarrera]

I had this exact problem and it was the first cause mentioned by mgc above - the tube to the expansion tank was blocked (I'd just replaced my temp sender and guess I dislodged some crud which blocked the pipe). Replaced the pipe and all was fine.

[politeperson]

I had this problem too. The water was not circulating because the water pump impellor had disintegrated.

When the engine is hot, the top hose and the bottom hose should be hot. That is how you check the circulation.

If the top hose is hot and the bottom hose is cold, water is not circulating and you had better turn it off quick.

It is relatively easy to change the pump if the bolts will come out.

The fans will still come on even if you have no water pump. I found this out.

Is the temperature gauge indicating the car is getting too hot?

Good luck.

James

[christopher storey]

I cannot agree that the bottom hose should be hot. There should be a perceptible difference in temperature between the top hose, which has uncooled water exiting the engine, and the bottom hose which should be returning water cooled by the radiator back to the engine. If both are hot to the same degree , then the radiator is not working .

Nonetheless, the suggestion that water pump flow should be checked is a good one. The method slightly depends on exactly which manifold and thermostat system you have . In general terms it can be checked when the engine is cold, and the thermostat therefore closed , by disconnecting the small by pass hose at the radiator end and seeing that water is pumped out ( into a bucket of course ) with the engine started

[politeperson]

All right Christopher, not hot-warm.

Or even better, the bottom hose should be perceptibly warmer than the ambient temperature, yet cooler than the top hose.