Technical Brava 1.6 sx overheating

[Big_Al]

Hi,

I bought my car about a month and a half ago and it all seemed fine. I was sitting in traffic the other day and noticed the engine was running a bit hot so i stuck the heaters on full which cooled it down fine. then the heating system cut out so i pulled over and let everything cool down. Got it back home and had a look around under the bonnet, couldn't see any leaks so i tryed bleeding the system. I got nothing from the radiator bleed valve and only steam from the heater valve. I drained the whole system and took the thermostat off for testing. The valve seemed to be opening fine, letting plenty of water through, then closing firmly when cooled down. I flushed the radiator and blew through the heater return pipe to check for blocks but they both seemed fine. I then put the thermostat back on and refilled the system. I couldn't seem to bleed the system properly and was again only getting steam from the heater bleed valve. I tested the pipes for heat and found the heater return pipe was not getting hot so i took both pipes off and connected them together to bi-passed the heating matrix. I tryed bleeding the system again but was still only getting steam. I don't think i've got a problem with the coolant pump as i'm getting plenty of pressure in the system. i've also checked for a head gasket faliure and dont think thats the problem.
I also noticed quite a loud knocking coming from the header tank, not sure whether it is bubbles or somthing in the system (i can't see anything in the tank). The fan seems to flick on and then go straight back off agian when the engine is warm. i put a short across the teminals of the radiator thermister and the fan works fine so possibly a dodgy part there. i also noticed that the bottom header tank hose was not getting hot, even though the radiator is??!! Anybody got any ideas for what i can try next?

 

[Deckchair5]

Nice descriptions by the way but what a load orf headaches!
Taking it one bit at a time

"the engine was running a bit hot so i stuck the heaters on full which cooled it down fine. then the heating system cut out"
How hot did it get? In the red? Then "the heating system cut out" you mean blowing cold? OK air lock,blockage or loss of coolant. Where did the coolant go? Was it low already? Too late anyway now as you have an air lock in the heater circuit if it's blowing cold

The rest sounds like it could all be caused by a system failing to bleed properly on refill

"I got nothing from the radiator bleed valve and only steam from the heater valve". The system refill isn't right. There's either air or a blockage

"I also noticed quite a loud knocking coming from the header tank"
That's steaming hot water hitting stone cold water in the pipes

I'd drain the whole ot down and refill EXACTLY as it says in the Haynes manual

Good luck. I know air locks can be a bitch sometimes and it's no fun messing with scolding water but the Bravo is usually OK to refill if you do it as per Haynes

 

[Big_Al]

Cheers for the helpful reply,

well, i drained the system again and refilled it following the haynes manual but i'm still having problems. as the engine is warming up the pipes are still getting hot but i'm still only getting steam out of the heating blead valve. as the engine was running i removed the header tank cap and watched what was happening to the coolant level. after a few mins of running i noticed that the coolant started to rise to the top of the tank, the fan then came on and the coolant level droped down to around the min level on the tank. after about only a second the fan switched off and the coolant started to rise again. there were also bubbles coming up thought the tank. this process repeated itself every min or so for about 10 mins until i turned the engine off. if you can offer any ideas then i would be greatful.

cheers

 

[Deckchair5]

Well that's classic air lock/blockage or head gasket symptoms

Which pipes are getting hot? Radiator input/output AND heater input/output?

When you're bleeding the system do you get water coming out of the heater circuit bleed screw? Are you sure the heater is in the HOT position when you're refilling?

When you fill the header tank to the very top then you've just got to get water coming out the heater bleed screw. If not, "why not?" I'd be asking

If you then get just steam out of the heater bleed screw then the heater circuit isn't filled properly or has developed an air lock or blockage

Are the heater inlet and outlet pipes both getting hot like they should?
Are you getting steam out the exhaust?
Do you have misfire on start up?
Does the water gush out of the header tank if you have the top off?

 

[chuck]

On my old car, I had one incident where the radiator bleed screw broke. Loss of pressure, so car heated up very very quickly (like only a couple streets).

I notice on my Brava that after a long drive, then following slow traffic, the engine does get hot (a notch above the centre mark). The heater trick does help.

Am I right in saying that you can drive without overheating, but just get no heat from the heat blower ?

My problem was an overheating problem with my brava, it was all due to air locks when I refilled the system. I never got any heat out of the blowers.

Mind you, I know my cooling fan works, but it very rarely comes on unless the engine is getting closer the red temp mark.

Some of the guys on this site gave me some good tips.

This is how I do mine now:
1) Check all pipes are tightened up. With radiator bleed screw and heater bleed loose, fill coolant (very slowly) to the maximum level. The manual says keep filling until coolant comes out of the bleed screws then tighten the bleed screw, but I never see any coolant coming out of them even filling to the brim.
2) Put the rad cap on and tighten the bleed screws.
3) Run the engine idle with heater on full and maximum heat. When the temp is rising (1st quarter - not too hot at this stage), I go round and squeeze the radiator pipes to help release any air locks [don't do this if the pipes are too hot]. When the engine gets past the middle, stop the engine.
4) At this point, I go round to the heater bleed screw and undo it just enough to hear hissing. Wait for hissing to stop, then tighten it again.
5) Repeat step 4 with the radiator bleed screw [just becareful where you lean and put your hands, as hoses, rad may be hot]
6) Let the car cool down for a good 10 mins.
7) Now undo the radiator cap very slowly [let the pressure escape first before undoing it completely].
8) Top the coolant up to slightly above the maximum (for the 1st time round, I just fill it upto a couple of inches below the brim), and screw the radiator cap back on.
9) Repeat step 3...Now just forget about the car and let it cool down for a good couple of hours.
10) When you return, re-check coolant level, and top up to the maximum if needed.
11) Now basically, I just kept repeating steps 3-10, except now on step 8, only topped up to the maximum limit. After a couple of goes, instead of just idling the car, I gave the car a short spin and see if the temp is maintained at the centre mark.

At some point, you should not need to add any more coolant as it would settle to somewhere around the MAX mark. With a bit of luck you should get heat coming out of the heater blowers. Coolant should start coming out of the heater screw if you unscrew (very slowly again). There should bit a lot less hissing. The same should happen for the radiator bleed screw.

I know the method is very long winded. I'm sure there is a better, quicker way...but this worked for me. I hear that some guys fill the coolant up with the car at an angle (not sure if with engine end up - facing uphill for example) to help reduce the chance of air locks.

Hope this works for you too.

If you are still getting steam out of the heater screw, does look like a blockage or perhaps there is a leak somewhere which stops the coolant from being circulated in the heater circuit (e.g. loose pipe connections, bad/cracked hoses, maybe the heater bleed screw has gone)...just like my knackered bleed radiator bleed screw.

Good luck

 

[Helz]

You'll never hear the fan kick in unless you turn the engine off and get out of the car anyway.