overheating

[mathiszig]

help
my lovely R4 dolores is playing up. her temperuture light is coming on after about 15 minutes driving, goes out once in a while, then comes on again. fan is working and kicks in fine when i checked it. had connections to thermostat cleaned and changed but still no good. worse in heavy traffic and as i live in central london not ideal. can i ignore this????lucie

 

[Steve Hennessey]

Did you have a new thermostat fitted (in the top hose) and did they bleed the air out of the system properly? Is the fan belt tight? Check these first. If the light still comes on you also need to check if the water is boiling - you can tell by looking at the overflow bottle - if there are loads of bubbles accompanied by noises then it may be a head gasket. If there is no boiling then it's likely to be the temperature sensor.

You don't say what model R4 you have.

Steve

 

[mathiszig]

thanks steve
its a 1984 GTL. had it serviced and some work done to get it through the MOT but don't think they touched radiator etc. fan belts checked and tight. will look out for bubbles in expansion bottle when next too hot. ( is that bootle on right side of wing?) what if thermostat faulty. could i take that out until i can get back to garage to stop overheating?

 

[Steve Hennessey]

Yes, it's the bottle that's held on by a big rubber band and a thin pipe goes from the radiator to it. I would not recommend that you remove the thermostat just yet. One way to see if it's working is to start the engine from cold, pull the choke out a little just enough to get a fast idle and after 5 mins hold the heater hoses (make sure the tap is set to HOT) to see if they are getting warm. Then hold the top hose to see if that's getting warm - try every few minutes. If it does get warm and then hot after a while, the thermostat is working OK. If the warning light comes on and the hose is still coldish, it may be the thermostat is faulty. Do give the above test 20 mins max. Get a new thermostat, fit it and bleed the cooling system (don't forget to anti freeze) and repeat the test but leave the engine running long enough to check the fan is working. If the engine boils after that you're looking at a head gasket job, but please get someone knowledgable to do the job as this engine has wet liners.

Steve

 

[angel]

I would guess the thermostat,too.It is very easy to remoe and you can then immerse it in a container with boiling water an see if it opens (better still to have a thermometer so you can see the exact point of opening).The thermostat should be installet with the wax container ("pointed" side) towards engine, I once had a R4 owner complaining about rapid overheating and the thermostat had been installed the wrong way round by a "brillant" mechanic!!! Some time ago, I blew a head gasket on my '75 R1123 because the impeller came loose on the water pump spindle, so anything seemed to work fine from the outside,except that the pump didn't pump at all!...

 

[malcolm]

The electric fan is controlled by a thermal switch on the outlet of the radiator. If the fan is coming on then surely it would suggest that the water in the radiator is getting hot and therefore that the thermostat is working?

Is the car loosing water and does the heater work correctly?

There should be a red (I think) wire going to the temperature sensor that is bolted on to the top corner of the engine on the rear left side (when looking forward). Check that wire hasn't burned away on the exhaust manifold and isn't shorting anywhere.

If it is a real cooling problem it needs looking at quickly as the head gaskets can go on the R4 and that's a pain. I'd also want to make sure the system was bled correctly (there is a bleed screw sticking out of the bulkhead that comes from the heater).

 

[mathiszig]

hi
i am getting confused and refusing to even contemplate head gasket as this sounds like a big problem. have tried and checked all i can. heater seems to be working and coming on fine, no leaks anywhere, no bubbling in expansion bottle...... however,detected that fan sometimes not on when red light indicating overheating. i am hoping now that it is the temperature sensore, as problem intermitant. yes??

 

[malcolm]

The temperature sensor is a possibility - but normally they fail in a random way rather than light up just when the engine is hot so it's not the first thing I'd replace.

I'd be worried that there might be some air in the system, as that would fit the symptoms. It's well worth having the system bled just to be on the safe side.

It might be worth changing the thermostat too. If it was sticking sometimes but working sometimes then that might cause the same set of problems, although it wouldn't explain the light coming on while the fan was running.

If the engine doesn't lose water then the head gasket is OK (but it's worth getting to the bottom of these cooling system issues as the gasket can fail due to overheating.)

 

[Simon.AU]

What sort of radiator is it? An aluminium one or a brass one? The alloy radiators seem subject to furring up internally if coolant changes are delayed or hard water is used. The alloy ones generally have to be replaced if corroded internally.

If it is a brass radiator it could be blocked, what is the condition of the coolant?