Cooling advice please

[Stuart Delahoy]

I have been putting a few miles on my 1966 R4 before going to Thenay, and all was well until today.
The coolant has started pressurising back into the expansion bottle, which got very hot. The oil is clear and no sign of any in the water.
Is this normal or a sign of head problems?
The water its self is a dirty rusty brown colour and I wonder if draining and flushing might help.
Any advise would be great as time is running short, over to you...
Thanks Stuart.

 

[malcolm]

We put a new waterpump on about 5 years ago, flushed the system and filled up the coolant with antifreeze. That's unlikely to be the problem.

After leaving the car overnight try removing the radiator cap and seeing if the system needs topping up from there. If so there is likely a leak. Before checking the radiator cap try removing the expansion bottle cap when the car is cold. If you get a hiss removing the cap it is a sign of head gasket trouble.

 

[André4Renaults]

I was going to suggest flushing and checking the pump, but that's already been taken into account. Is the thermostat sticking? Run the car with the heater fully on & check that it works O.K. If not, it's possible there's an air bubble or it's blocked. Worth a look.....

Flushing wouldn't do any harm anyway.

 

[Stuart Delahoy]

Thanks both, the heater runs hot so I dont think there is air in the system. Will check for the hiss tomorrow.
Would you advise a compression test Malcolm?

 

[malcolm]

I don't think a compression test would show you anything related to the cooling. Those checks I mentioned would give a better clue.

Is the water boiling and coming out of the expansion bottle? Or is the level just rising? It could be the thermostat is stuck closed as Andrew says.

 

[Stuart Delahoy]

Checked the expansion bottle, no hiss.Checked the level in the rad, its full, and after a drive today all appeared well.
When it had cooled down I opened the rad cap again and the bleed valve on the bulkhead, no air in the system at all.
So all looks good, but I might take the thermastat out anyway...
Malcolm I thought a compression test would show up any head gasket issues?

 

[malcolm]

Compression test will mostly show up leaky piston rings or valves that aren't sealing properly. Mostly it will show you are not using the car enough. If two cylinders beside eachother have low compression then the gasket has probably failed between those cylinders. The leak needed to push water out of the system is tiny and wouldn't be significant by comparison.

A head gasket problem would tend to introduce air (well, combustion gasses) into the coolant. The air causes hot spots which boil causing more air (well, steam) which quickly stop the waterpump from circulating causing more steam and much bubbling from the expansion bottle. Once everything has cooled down overnight if you get a hiss when removing the expansion bottle top it is a sign that there is more stuff in there than there was before it was last tightened and it can be air from a failed head gasket.

Don't forget the expansion bottle is called that for a reason - it does get a bit more full when the engine is hot. Pop down for a test run - I can do tea.

 

[malcolm]

Ought to update what we found in case anyone else has the same problem. There were tiny leaks from the top hose and radiator cap which were stopping the cooling system from pressurising. The early cars with the fan driven full time will run without pressurised coolant, but the water overheats when the engine is turned off and bubbles into the expansion bottle.

How did it perform going down to Thenay?

 

[Stuart Delahoy]

Well we got there and back...But she continued to overheat at every oppertunity!
The water level would rise in the bottle and if we continued to far bubble and nearly boil. We ran in short bursts of not much over an hour or so, when possible, and had to put the heater on to bring the temp down. Which when the outside temp is in the 30's is fun...
So the problem is still there.
I am thinking a re-cored rad next?
Any thoughts...

 

[JonathanT]

Hi Stuart I suspect you may have the earlier radiator sited close to the engine block. If not and its at the front I got a brand new rad for about £40 delivered from Germany I think ?