Overheating

[nickharman]

My 1987 R4 is overheating, light comes on. The electric fan is not coming on, but I have verified it works by bypassing the switch. It runs fine

So my first thought was it was that.

But perhaps not. The upper hose is very hot, the lower hose merely warm.

Would that perhaps suggest the water is not flowing around the radiator and the fan switch is not coming on because it’s not getting warm?

Would that simply be the thermostat at fault? Although the upper hose is hot so water is surely being released to flow into that pipe?

Could it therefore be an almightily blocked radiator? The car gets very little use, it's been barned for a year in France while I was trapped in UK

Thx

 

[jjad]

When you say the top hose is very hot, is it hot all the way along to the radiator?

I would expect the lower hose to be cooler, but if it were a lot cooler, then your radiator might well be (partially) blocked.

You could try removing the radiator and flushing it out, but it might be better to replace it if it's old and potentially damaged.

 

[nickharman]

Well it seems to be, too hot to hold. Whereas I can hold the lower hose comfortably.

The rad is almost certainly 1987 vintage, I just replaced the 1968 rad on my sunbeam as it was blocked so these things do happen! The fact the electric fan sensor is not triggering does suggest poor flow

70 euros for new one, im not back until january earliest. I may try a flush first!

n

 

[nickharman]

actually I have just bypassed the fan thermo and forced it on, the car is now not overheating at rest
So it is I think just a new thermo switch needed

 

[jcarruthers2]

Hi Nick

I have been following your thread with interest. If your R4 has been standing for a long time unused but was not overheating last time you used it, there are a number of common culprits.

You have ruled out the radiator fan which you have tested by bypassing the switch. One of the culprits due to longstanding non-use could be the thermostat. However, as you have mentioned the top radiator hose is getting hot (this suggests the thermostat is doing its job). I would therefore place the thermostat fourth in line to check. My rule of thumb is to start with the easiest/cheapest to change culprits first.

1) Check the radiator fan switch spades/connectors have not become corroded/loose. Abrade with emery/crimp up/change loose connectors.

2) Check for an air lock in the cooling system by bleeding the cooling system. Disconnect the expansion bottle (when engine cold) from the retaining strap. Tie the expansion bottle (with the cap off) to the bonnet catch at the top of the inside of the bonnet (with the bonnet propped open). Ensure the bottle is filled to max. The aim is to force the air out of the system as the expansion bottle is now in an elevated position. Locate the bleed nipple protruding from the bulkhead carburettor side. Unscrew the bleed nipple cap. Check for air/air bubbles in the coolant. Screw the cap back on for now. Make sure the interior heating is in the on position. Run the engine. Check for air locks again by partially unscrewing the bleed nipple cap. When there are no more air bubbles, tighten the bleed nipple screw cap again. Wait for the engine to reach temperature. Do a visual check for any leaks. It might be worth tapping the metal side of the radiator fan switch gently with the end of a weighty implement to try and spring it into life. Keep an eye on the expansion bottle for boiling over and the coming on of the temp warning light. If so the engine is overheating, switch off the engine immediately.

If you notice the interior heating starting to warm up/blow hot whilst waiting for the engine to reach temperature, this is a good sign. If the heating blows cold it suggests there is still air in the system/or another problem. If the fan kicks in once the engine has reached temperature without the red light coming on or the water in the expansion bottle boiling over, this is a sign that everything is ok.

3) If the car is still overheating. Wait for the engine to cool down. Change the radiator fan switch and carry out the procedure in 2) again. If the car is still overheating......

4) Wait for the engine to cool down. Remove the thermostat. Check/change the thermostat. Repeat the procedure in 2). Hopefully, all is ok by now. If not....

5) Further investigation is required.

Hopefully you will be able to resolve the issue with minimal intervention.

 

[orsome]

take out the thermostat completely as i have done after a full motor resto to avoid overheating and damages, but i only drive during warm wheathers

 

[nickharman]

Hi Nick

I have been following your thread with interest. If your R4 has been standing for a long time unused but was not overheating last time you used it, there are a number of common culprits.

You have ruled out the radiator fan which you have tested by bypassing the switch. One of the culprits due to longstanding non-use could be the thermostat. However, as you have mentioned the top radiator hose is getting hot (this suggests the thermostat is doing its job). I would therefore place the thermostat fourth in line to check. My rule of thumb is to start with the easiest/cheapest to change culprits first.

1) Check the radiator fan switch spades/connectors have not become corroded/loose. Abrade with emery/crimp up/change loose connectors.

2) Check for an air lock in the cooling system by bleeding the cooling system. Disconnect the expansion bottle (when engine cold) from the retaining strap. Tie the expansion bottle (with the cap off) to the bonnet catch at the top of the inside of the bonnet (with the bonnet propped open). Ensure the bottle is filled to max. The aim is to force the air out of the system as the expansion bottle is now in an elevated position. Locate the bleed nipple protruding from the bulkhead carburettor side. Unscrew the bleed nipple cap. Check for air/air bubbles in the coolant. Screw the cap back on for now. Make sure the interior heating is in the on position. Run the engine. Check for air locks again by partially unscrewing the bleed nipple cap. When there are no more air bubbles, tighten the bleed nipple screw cap again. Wait for the engine to reach temperature. Do a visual check for any leaks. It might be worth tapping the metal side of the radiator fan switch gently with the end of a weighty implement to try and spring it into life. Keep an eye on the expansion bottle for boiling over and the coming on of the temp warning light. If so the engine is overheating, switch off the engine immediately.

If you notice the interior heating starting to warm up/blow hot whilst waiting for the engine to reach temperature, this is a good sign. If the heating blows cold it suggests there is still air in the system/or another problem. If the fan kicks in once the engine has reached temperature without the red light coming on or the water in the expansion bottle boiling over, this is a sign that everything is ok.

3) If the car is still overheating. Wait for the engine to cool down. Change the radiator fan switch and carry out the procedure in 2) again. If the car is still overheating......

4) Wait for the engine to cool down. Remove the thermostat. Check/change the thermostat. Repeat the procedure in 2). Hopefully, all is ok by now. If not....

5) Further investigation is required.

Hopefully you will be able to resolve the issue with minimal intervention.

Thanks, I shall keep your very useful notes,

With the cooling fan forced on by bypass, the overheat when standing has stopped. So I think I need a new fan switch

I can't go too far test driving as I have no CT and no CG, and I can't get a new CG without a CT. The wonders of French bureaucracy!

So looks like its back into the barn until I can return after Xmas, assuming we dont all get locked down again!

 

[jcarruthers2]

Hi Nick

I would say in your case the most likely culprit is the radiator fan switch. However, Renault 4s are known to throw you a curve ball on occasions!

 

[nickharman]

Hi Nick

I would say in your case the most likely culprit is the radiator fan switch. However, Renault 4s are known to throw you a curve ball on occasions!

Indeed, although with the fan running the warning light does not come on.
I shall order up a new switch to install january.