No heat after radiator replacement

[Niels Svane]

Hi everybody

I replaced my old wornout radiator for a new one this weekend, and flushed the system before the change as prescribed. Afterwards I vented the system. The thermostat was also replaced.

There was no problems with overheating on my 120 km way home from where I fixed the car, with a steady 95 km/h, but when I overtook a lorry at 100 km/h, the water overheating light came on. Then I turned on the heater and realized that no heat came out at any point. Theres still no heat, after numerous vents of the system, and now I dont know what to try out I have massaged all hoses and cleaned out one blockage at the carburettor water channel.

Should I take the whole heater apart and look inthere for answers? I have checked that there is flow through the thermostat and the two large hoses, and also through the waterpump.

 

[André4Renaults]

In spite of all your efforts I reckon you have an air block in the system somewhere..... I'd suggest you wait until you have some time and then start the car and put the heater controls to full hot with the fan on. Eventually you should have hot coolant circulating through all the system, including the heater. By feeling along the hoses and massaging them you ought to be able to find where the heat is and where it isn't. Keep topping up the system and occasionally raising the revs to about 2,000 rpm may help move things about. You may still have some silt in the pipes.

I've spent AGES bleeding cooling systems on cars over the years! If you REALLY want a challenging system to bleed, try a late model Skoda Estelle with the engine in the back & the radiator in the front of the car..... Believe me, that one takes some time to get right!

More advice if you need it!

 

[Niels Svane]

When blowing softly in the hose running into the heater from the water pump, coolant flows from the corresponding hole in the pump, so I dont think theres any large blockages.

 

[Niels Svane]

Haha okay I'll try again tomorrow then! The hose running from the pump to the heater through the firewall did not get very hot btw, and the hose running to the pump from the firewall (with a T-junction to the carb) didnt get that hot either.

The two large hoses from the radiator went quite hot quite fast. And there is no hint of heat coming from the heater, not even a little change.

 

[JonathanT]

I'm sure you have but just in case.....you've seen the little air bleed pipe coming through the bulkhead above the heater within the engine bay? It has a screw closure on the end and the pipe is about 15mm diameter. Sometimes air locks come out on their own if you open such vent pipes

See in the middle section two big heater hoses and one little one tip centre right

 

[JonathanT]

It's probable the air lock is still in the heater matrix . You blowing just moved the bubble along causing it to come out of the corresponding pipe and appear ok but not if you see what I mean

 

[André4Renaults]

The hose running from the pump to the heater through the firewall did not get very hot btw, and the hose running to the pump from the firewall (with a T-junction to the carb) didnt get that hot either.
The two large hoses from the radiator went quite hot quite fast. And there is no hint of heat coming from the heater, not even a little change.

The hoses to & from the radiator warming up quickly proves that the coolant is circulating through the engine and the radiator as it should. The hoses to & from the heater and the matrix contained therein NOT warming, even when the heater controls are set to "hot" means coolant is NOT getting through to & from the matrix. Try raising the height of the header tank so that it is higher than any other part of the cooling system, which will help move the air lock out of the heater matrix and will allow it to bubble out of the header tank.

 

[Niels Svane]

I have used the small vent-hose coming through the firewall extensively, dont worry I am beginning to suspect an airlock in heater matrix as the only possible culprit, as I dont know where any dirt should have come from. As with sudden pump failure. But standing by the car with the engine running, and the expansion bottle raised for more than half an hour is becoming a tedious task ;D I gather that its not harmful to drive with air in the system? As long as I dont drive too fast.

 

[André4Renaults]

If the warning light is coming on the engine IS too hot! Somehow this airlock needs to be shifted. Have you tried supporting the expansion bottle higher than the rest of the system by using a wire coat hanger passed through the bonnet struts? You could then rev up the engine from the carburettor & this should bleed the system.

Just a thought: are the heater controls working properly? Maybe they're not and THIS is the problem because they're not allowing the coolant to pass along the pipes. Worth checking!

 

[Niels Svane]

I have tried raising the expansion bottle while venting the system. I think the heater controls should be working as I havent touched them at all while changing the radiator. And they worked really well before.
I was going to dismantle the heatermatrix, but I would really like not having to bleed the whole system again. I'll try some more massaging, and venting tomorrow and see if it helps

 

[Niels Svane]

Hooraa! The solution was to drive until the car was warm, then raise the expansion bottle a lot, open the vent-hose, aaand revving the car to 2-3000 rpm's This was then repeated 4-5 times.
Presto: a lot of bubbles in the coolant, and warm hoses all around + a nice warm air in the cabin

So now I will enjoy the autumn, and then attach wheel arch liners and a tow bar, and then look for a classic combi-camp ("tent-wagon") and trailer, and buy 4 new tires next year

Thanks for the help and suggestions!

 

[JonathanT]

Marvellous!

Interested in your wheel arch liners....made any progress yet?
This is my next job. I have the idea that I might try pre made ABS plastic trailer mudguards cut and adapted to fit. Thinking they have a curved edge and are already near the right shape

 

[Niels Svane]

They are on the shelf ready to collect Made from aluminium with small flaps for drilling mounting holes. As I recall they should be lined up with existing bolts on the car.
They cost around 600-800 kr per end (69-92 £), and some 20-30 £ in shipping I gather.

 

[JonathanT]

Interested to see what they look like

 

[Paul Narramore]

I was interested to read about the lack of heat from the heater as over the past few days, I've had the heater on for the first time. It takes for ever for any heat to emerge from the inside grills and then only really with the noisy fan blasting away. I know the bleed whatsit has been bled so there should be no air in the system, but I intend to drain the coolant, flush through then add fresh antifreeze and water plus follow some of the advice written above to see if that improves matters.

 

[André4Renaults]

If there's some ("not a lot!") heat and the engine takes ages to warm up then it might be a themostatic problem. Although you'll have to bleed everything again it might be worth taking a look.

Sorry, but I was a great fan of the late Paul Daniels!

 

[benchseat]

"Lot of bubbles in the coolant" (post 21st September). I had that once. In fact looking into the coolant bottle and seeing the bubbles was the only visible sign of the problem.

Which was a blown head gasket. Might be worth pressure-checking the system to make sure that this is not an additional complication.

I had had a radiator hose rupture about a month previously but it took me that month to make the deduction.

 

[Paul Narramore]

Well the other day I raised the expansion bottle on my R4GTL then 'massaged' the top hose, and a great big glug of an air bubble appeared in the bottle. I slackened off the bleed screw and some air came out. The result is that the heater now heats!

However the coolant is still rusty orange so I shall drain the radiator, flush things through and add fresh antifreeze and water. Any tips on flushing the engine? I shall undo the bottom hose and the radiator cap then flush the radiator though. There is a tiny drain screw in the side of the engine block which looks damned difficult to get to so perhaps I will leave that well alone.

Up to my local Halfords today and searched through their antifreeze guide. Naturally the R4GTL is no longer listed but all Renaults listed are recommended OAT Ready Mixed or Concentrate. The alternative is Silicate Ready Mixed or Concentrate. I arrived home, looked on here and found zilch. I went to Halford's website and they recommend Silicate for pre-1998 cars and OAT for post-1998 cars. I have however bought the OAT stuff and cannot be bothered to take it back. I imagine that most pre-1998 cars had cast iron engines and post-1998 cars aluminium engines, hence the difference - I may be wrong - but hey ho, she getting some OAT and rainwater from one of my butts.

 

[reidalpine]

Hi Paul.if you can be bothered -I always boil the water to rid it of most possible oxygen, that way you will have much
less chance of Hot-spots due to air-bubbles afterwards.. -Reid

 

[Paul Narramore]

Reid, Call me sceptical but boiling water would convert H2O to H2 - hydrogen surely? My heater now works fine after massaging the rubber hoses, thanks