So I'm back! With a overheating question

[Niels Svane]

So the R4 has been standing for 3 weeks, with no overheating issues before. It emptied the expansion bottle at one occation though, and it has had some problems getting enough heat from the heater.

Today was it's first run and after 1 hour on the highway at 85-95 km/h the overheating light came on. I then slowed down and at a rest site I bled air from the system, and got home without further incidents.

- The head gasket seems to be fine
- It doesn't leak
- The heater now works better
- The radiator is not overly gunked up in dead insects and what-not
- The radiator and thermostat is a bit over one year old, and should work fine (it's a 75 C thermo I think).

So: Would you think I just should keep on driving, or pull of the heater matrix to look it over? Or maybe do something else?
I've heard that the waterpump 'wheel' might turn with a cold engine but loosen at speed with a warm engine.

 

[benchseat]

I should try and find out why the expansion bottle emptied.

If, after you had refilled the expansion bottle, there was an airlock in the system, that would explain the overheating, the heater not working properly and why you needed to bleed air out. But it doesn't explain why the loss of coolant occurred in the first place.

The heater matrix is connected "in parallel" with the radiator and so it wouldn't cause overheating simply by being blocked. After all, you presumably turn off the heater valve in hot weather and then no water flows through it anyway.

On 845ccs the alternator is also driven from the water-pump shaft. So if the water-pump belt were slipping you'd see the alternator warning light come on as well.

Initially I'd be inclined to keep driving and see if the problem has been sorted. If overheating or coolant loss persists I'd suspect a failed head gasket. You can easily detect this : take the cap off the expansion bottle, run the engine and see if you can see any little air bubbles coming up through the coolant. Quite often this is the only symptom. But it would be enough to cause coolant loss over an extended period. Other possibilities : defective water-pump (but that is unlikely if you managed to bleed the air out : there must be positive pump pressure in the system), defective thermostat (remedy : remove it and see if overheating still occurs). Or a leaking hose or radiator cap (sorry if this seems like a bit of a no-brainer).

 

[Niels Svane]

The radiator cap is bone dry, all visible hoses are in fine condition, and it seems that no bubbles are to be seen in the exp bottle. It's a bit strange overall Before I suddenly saw that the exp bottle had emptied, the level had been stable for a year.

 

[malcolm]

The expansion bottle cap seal can cause problems - most of the overheating problems I have found are due to the seal failing and the system not being able to pressurise so the boiling point it too low. Boiling makes bubbles and causes overheating.

The check I use for head gasket is remove and replace the expansion bottle cap first thing in the morning when the car is cold. Go for a run, then next morning check again. If you get a hiss when you remove the cap it means more stuff is in there than last time - normally head gasket.

 

[Niels Svane]

Regarding the head gasket; the exp bottle doesn't smell the least of petrol.

 

[Niels Svane]

Btw I found a hose/pipe going from low in the firewall down to the bottom of the engine bay with nothing in it's end. What is this for? I gather it's some kind of breather pipe.

 

[André4Renaults]

Regarding the head gasket; the exp bottle doesn't smell the least of petrol.

This suggests (only suggests!) the head gasket is in good order and the problem is elsewhere. There have been a number of threads on the forum along these lines and it seems the Renault 4 is not the easiest of cars to bleed the air from. The heater needs to be on full HOT while this operation is being carried out and the expansion tank should be supported significantly higher then the engine (perhaps tied to the bonnet, to keep it high up) and the bleeding points opened to allow the air to escape. The car should be parked on level ground, too. It's a case of filling the expansion tank, starting the engine and allowing it to warm up and allowing air to escape from the bleed nipples until coolant runs freely. Keep the revs at tick-over until the engine has warmed and then watch for bubbles escaping through the water in the expansion tank. This means the thermostat has opened and confirm this by checking both top & bottom hoses to & from the radiator are hot. Also check the hoses to and from the heater matrix are hot; if they're not, there's a blockage there, either of air or crud & it needs investigating. If all the pipes are warm, continue watching for bubbles and when you're satisfied the air is out, put the expansion bottle cap on (check the seal and that it's the right cap!) and switch off the engine. Let everything cool down, put the expansion tank back where it should be, note the level and later go for a drive with the heater full on, noting how hot the output is. Listen for noises and on your return let everything cool down again & check the level. It should be more or less the same if you've done everything properly and there are no problems with the cooling system.

 

[angel]

Btw I found a hose/pipe going from low in the firewall down to the bottom of the engine bay with nothing in it's end. What is this for? I gather it's some kind of breather pipe.

It's a drain pipe for rain water that eventually gets in the heater locating compartment through the fresh air inlet. It has nothing to do with the cooling circuit so don't worry.

The original water pump had its impeller held on the shaft by means of a pressed-on brass ring. It can work loose and the impeller will turn freely on the shaft - happened to me once and I blew the head gasket. It's worthwhile checking this if everything else is OK.

 

[Niels Svane]

I'll have to test if it keeps overheating and then throw it at a trip to Sweden full of guys and beer in October.
Right now I'm focusing more on an ES2 and Model 18, that might find their way into my garage next week!

 

[Niels Svane]

It seems like it now really delivers some heat in the cabin, and the overheating problem looks to be gone for now. The water level is stable and the exp. bottle smells like coolant, not petrol after a long run.

 

[SJC400]

Hi, this problem screems "THERMOSTAT" to me.
Seen this problem many, many times, people changing all kinds of bits including head gaskets, when it's a simple Thermostat fault.
If you have'nt already changed it, it's cheap, easy and worth changing before it happens again.
Hope that helps?

 

[Niels Svane]

The thermostat is brand new (ish) i.e. 10 months old.

 

[Niels Svane]

I got some distraction from the car. A 1956 Norton ES2 to be washed, polished, have a new amal 376, a recon. magneto, new tires and tubes, new oils and a bit here and there.
I already love it.

 

[SJC400]

Well, it's the cheapest option to throw in another thermostat, before anything else!
Love the bike, a real 'cracker'

 

[Niels Svane]

I found the culprit. While driving 400 km into Sweden with friends in a 2CV and a modern Volvo, the car overheated again. The when we reached our destination (a small cottage), I found that one of the pipes was cracked. No mechanic would help and had no interest what so ever, so I fixed in with an old bicycle tube put into the pipe and also around the hole on the outside. Then we drove home some days later with no overheating, lots of heat in the cabin, and a steady 95 km/h.
The day after I took the car to a large old-vehicle fair here in Denmark, where it was displayed along my norton and some other bikes, and the I drove it back in the rain at a 100 km/h with no troubles.

Got a new (one more) Norton now btw. Had to buy it at 3700 pounds
I'll drive this one while I get the ES2 going.

 

[SJC400]

Excellent improvisation, I like it!

 

[Niels Svane]

It has worked flawlessly. The inner tube I've put in goes around 12-15 cm into the cracked tube, thus all water is delivered at a lower point than the crack. The rubber of the bicycle tube really seals everything up but in a while I'll look into how it handles the hot coolant.

Luckily the crack wasn't at a low lying pipe, where all water had to come off to fix it.