Viva OHC Overheating

[MattHC1600SL]

Hi evryone, have just used my 1971 1600 OHC HC properly for the first time this year tonight. Its got an overheating problem which seems to have got worse since last year. Its always run hot at speed, but now its overheating and pushing water out on a long run. Round town its fine, just on a long fast run it throws coolant out. Its had a thermostat and rad cap recently, no leaks that I can see and im sure the head gasket is ok. Im thinking new radiator? Any tips on where to get one - perhaps its worth getting an uprated core at the same time? Any comments? Cheers, Matt.

[doss]

New thermostats can sometimes be faulty as I have found out in the past. Try running it without the stat and see if the water is circulating in the system ok. Usually if its getting round fine then the Rad is ok. If the stat is sticking closed it will usually mean the coolant under pressure will be forced out the overflow pipe on the Rad.

[dann01]

The above is correct, but I have found that a good back flush with some pressure behind it can't do any harm either. You may be surprised at the amount of gunk and *Bleep* that can be pushed out.

[HC]

Are the thermostat temperature and radiator cap pressure within specifications?

[MattHC1600SL]

Rad cap is new and correct. Its on its third thermostat - this ones a 82c opening. The odd thing is, I noticed when the car started to overheat the heater blew cold??? Any ideas? Still suspecting the radiator. Cheers for the suggestions so far. Matt.

[Clara]

If the heater is only kicking out cold air it sounds like a block somewhere in the system.

Do all the water hoses (any kinks?) get hot? You might (ok tiny might) be able to find a blockage hunting for a cold spot. Have you taken the pipes off to check that the connections haven't crusted full of rubbish?

Drain the radiator and get the hose pipe out and blast some water around and try and shift the rubbish that has gathered, take each hose off one at a time and make sure the water is flowing freely (i.e. you can't see a lunp of rust floating and blowing the water flow.)

[griffonmark]

Hi Matt, my beast has a 2300 engine and limited airflow which overheated badly and shoved coolant out the cap. I suspect my car has a HC1256 radiator. The core, not including tanks is 16 inch wide and 11 inch tall. It was fitted with an aftermarket electric fan, siezed solid. So I went to my local scrapyard and for £15 bought a Rover 620 TD non aircon 1995 fan & cowl which fits great with slight cutting of cowl and runs continuously. The car got to temp quick and on tickover was fine. However, on driving it cooked bad, then cooled down in traffic. I took off the pressure cap and it was clear the water pump was shoving the water round. The rad was hot top and bottom. No thermostat was fittted. I had the radiator triple cored (not cheap at £96), it is now thicker, and used draught excluder to make the fan cowl seal to the inside of the radiator. Problem cured! Car now runs a bit cool so I am buying an adjustable thermoswitch. Good luck, Mark