Coolant problems
Discussion
My 4.5 Chimaera (2000) has started to blow coolant out of the expansion chamber. It started quite suddenly without pre-indications. The radiator was re-cored about 1000 miles ago and for the 1000 miles or so I had absolutely no problems. My first thoughts were that the problem was in some way related to the new radiator, but I cant find anything wrong with it, and the cooling system has been extensively and repeatedly bled. The car does not run hot, or at least the temperature gauge never goes above about 95 and the fans cut in. It has been suggested that it may be a blown head gasket, but no exhaust gases are detected in the coolant, and I am told that blown head gaskets are quite rare on the Chimaera. A cracked or porous block has also been suggested, but I don't appear to get hugely high pressure in the expansion chamber, and the engine does not appear to run hot. When I leave the car warming up and ticking over, the expansion chamber fills up and overflows. I wonder if anyone has come across this problem before ?! Any suggestions as to cause greatly received !
IBK said:
My 4.5 Chimaera (2000) has started to blow coolant out of the expansion chamber. It started quite suddenly without pre-indications. The radiator was re-cored about 1000 miles ago and for the 1000 miles or so I had absolutely no problems. My first thoughts were that the problem was in some way related to the new radiator, but I cant find anything wrong with it, and the cooling system has been extensively and repeatedly bled. The car does not run hot, or at least the temperature gauge never goes above about 95 and the fans cut in. It has been suggested that it may be a blown head gasket, but no exhaust gases are detected in the coolant, and I am told that blown head gaskets are quite rare on the Chimaera. A cracked or porous block has also been suggested, but I don't appear to get hugely high pressure in the expansion chamber, and the engine does not appear to run hot. When I leave the car warming up and ticking over, the expansion chamber fills up and overflows. I wonder if anyone has come across this problem before ?! Any suggestions as to cause greatly received !
Maybe replace the cap before you start worrying?
I had a problem a couple of years ago with the system not holding pressure. It would vent though the cap every time a came off the motorway after a run.
Replaced the cap (with a non-VW pattern part) and it still over flowed! Replaced again with a Genuine VW part – problem fixed.
Did you get a VW cap? Any idea what sort of pressure is being built up causing the cap to vent? Is the new cap still venting at too low a pressure?
Replaced the cap (with a non-VW pattern part) and it still over flowed! Replaced again with a Genuine VW part – problem fixed.
Did you get a VW cap? Any idea what sort of pressure is being built up causing the cap to vent? Is the new cap still venting at too low a pressure?
As PPTVR says, they usually find their own level. Mine runs about an inch from the bottom of the expansion tank. Are you caught in a loop where you are topping up evacuated coolant via the expansion tank to too high a level & it is simply dumping it again?
Also, to top up the system you must do it via the swirl pot & fill it to the brim. If you don't, you'll get trapped air in the system which can cause your problems, but I take it you know this as you mention bleeding the system?
Also, to top up the system you must do it via the swirl pot & fill it to the brim. If you don't, you'll get trapped air in the system which can cause your problems, but I take it you know this as you mention bleeding the system?
Many thanks for suggestions. I wonder whether the re-corded radiator has resulted in the expansion chamber taking less than it used to? Used to run half full. Will try running with less. Will check if cap genuine VW but pretty sure it is. Have had thermostat modified so is permanently slightly open; this was to help bleeding. Car runs cooler. Yes, thanks, I check swirl pot and fill from there. Will try taking car out again tomorrow.
Found that expansion chamber cap was not genuine VW/Audi and so replaced with a correct one. This improved things so that no loss of coolant when simply warming up. Fans cut in as expected. Went for drive and initially heard strange whistling noise for a while when accelerating ....no idea what that was...it stopped after a while. After about 4 miles pulled over and looked under bonnet and found no coolant lost. Drove for a little longer then came home where I found, as before, coolant had been blown out of expansion chamber! As car cooled lots of bubbling/gurgling sounds from both expansion chamber and from the engine! No idea what is going on! Any more ideas please ?!
IBK said:
Found that expansion chamber cap was not genuine VW/Audi and so replaced with a correct one. This improved things so that no loss of coolant when simply warming up. Fans cut in as expected. Went for drive and initially heard strange whistling noise for a while when accelerating ....no idea what that was...it stopped after a while. After about 4 miles pulled over and looked under bonnet and found no coolant lost. Drove for a little longer then came home where I found, as before, coolant had been blown out of expansion chamber! As car cooled lots of bubbling/gurgling sounds from both expansion chamber and from the engine! No idea what is going on! Any more ideas please ?!
The bubbling is the water boiling, are you sure the water is being pumped around the engine correctly? and i would double check there are no hc's in the water robHave you re-primed the system via the swirl pot? If the expansion pot is ever allowed to run dry you will end up with air in system. This cannot be corrected by refilling at the expansion pot; the purpose of the expansion pot is to manage the variable volume, not to prime the system. It is common under these circumstances for Chims & Griffs to throw water out of the expansion pot. That refills the pot hiding the fact that it had been dry. When this slug of air passes through the pump the coolant flow stalls resulting in boiling in the block. This will throw coolant out of the expansion pot cap and also jog the coolant so that the slug of air moves away from the pump allowing circulation to restart. Open the swirl pot, if there's an air space at the top then you must re-prime by filling at the swirl pot. Circulate the coolant and recheck the swirl pot level until it needs no fill. At this time it is worth setting the expansion pot to 1/3 full when cold.
My Griff 500 was spewing out round the cap for no apparent reason. I was topping it up on a regular basis. The cap was replaced and now it holds pressure. The old cap was only a year old. Once they've blown once they're never the same. Check with your parts suplier that you have the right cap because my local TVR dealer said there were issues with some caps. My expansion tank has only 10mm of water in the bottom when cold. It expels any more than this. The guys at Fernhurst say that this is not unusual and ok.
OK, many thanks for the suggestions.
I wonder if the water pump is failing.... the car heater appears to be working, but I wonder if the brief whistling noise I heard could have been the water pump ? Will check again for hc's and will look into pressure testing.
I have primed via the swirl pot and have checked that it was full each time before running, but maybe if there is an airlock this is deceptive. Will try priming again via swirl pot tomorrow.
Many thanks again.
I wonder if the water pump is failing.... the car heater appears to be working, but I wonder if the brief whistling noise I heard could have been the water pump ? Will check again for hc's and will look into pressure testing.
I have primed via the swirl pot and have checked that it was full each time before running, but maybe if there is an airlock this is deceptive. Will try priming again via swirl pot tomorrow.
Many thanks again.
If you take the brass screw plug off the top of the swirl pot when the engine is cold, it should be filled right to the brim with coolant.
With the plug still off the swirl pot, bleed the rad with the bleed screw until coolant comes out of it and then top the swirl pot up to the top if the level dropped at all.
Then replace the screw plug on the swirl pot and top the expansion tank up to whatever level you car seems to like. It varies from car to car.
With the plug still off the swirl pot, bleed the rad with the bleed screw until coolant comes out of it and then top the swirl pot up to the top if the level dropped at all.
Then replace the screw plug on the swirl pot and top the expansion tank up to whatever level you car seems to like. It varies from car to car.
Edited by JonRB on Thursday 16th July 09:04
Have replaced expansion chamber cap with another one and is better but still get overflow, and bubbling in engine when I turn off car.... so water boiling. Odd thing is that my expansion chamber has been happy at half full, and now is definitely not, and overflows, but this, as suggested, could be result of airlocks and boiling water. Certainly air is being generated from somewhere, either coming in, or from boiling coolant, or expanding from trapped air. Have bled system a a lot but will try again as suggested.
Very many thanks for all the comments!
Very many thanks for all the comments!
IBK said:
Have replaced expansion chamber cap with another one and is better but still get overflow, and bubbling in engine when I turn off car.... so water boiling. Odd thing is that my expansion chamber has been happy at half full, and now is definitely not, and overflows, but this, as suggested, could be result of airlocks and boiling water. Certainly air is being generated from somewhere, either coming in, or from boiling coolant, or expanding from trapped air. Have bled system a a lot but will try again as suggested.
Very many thanks for all the comments!
Go and get it pressure tested. Sounds like you're getting air in from somewhere. Very many thanks for all the comments!
I've got the same problem at the moment on my 98 Chimaera 400.
I prime the system with the heater controls set to hot as follows:
Open the expansion chamber and ensure there is about 2 inches of coolent present.
With the expansion chamber cap on, open the brass cap on the swirl pot.
Open the radiator bleed nut until the air has escaped and coolant comes out. The swirlpot levels drop.
Close the radiator bleed nut.
Top up the swirl pot to the brim, then replace the brass cap.
With the system primed, I take her for some spririted driving. The temp never excedes 90, the fans come on and off as expected, and there is no coolent loss.
When I switch the engine off, I hear gurgling from the expansion chamber and a faint hiss from the expansion cap.
Once the sytem is cool:
I open the swirl pot lid, the coolant is brimmed at the top.
Close the swirl pot cap.
Open the expansion chamber, the coolant has risen half / three quarters of the way up.
All the air is in the top of the radiator again. So I have to prime again! I just syphon the coolant from the expansion chamber into my Wife's pyrex jug for microwaving peas, then pour it into the swirl pot again. There's no coolant loss.
All extremly odd!! Any thoughts? I have a new filler cap on order:
http://www.ebay.co.uk/itm/COOLANT-TANK-CAP-NEW-GOL...
and will let you know how I get on with that.
I prime the system with the heater controls set to hot as follows:
Open the expansion chamber and ensure there is about 2 inches of coolent present.
With the expansion chamber cap on, open the brass cap on the swirl pot.
Open the radiator bleed nut until the air has escaped and coolant comes out. The swirlpot levels drop.
Close the radiator bleed nut.
Top up the swirl pot to the brim, then replace the brass cap.
With the system primed, I take her for some spririted driving. The temp never excedes 90, the fans come on and off as expected, and there is no coolent loss.
When I switch the engine off, I hear gurgling from the expansion chamber and a faint hiss from the expansion cap.
Once the sytem is cool:
I open the swirl pot lid, the coolant is brimmed at the top.
Close the swirl pot cap.
Open the expansion chamber, the coolant has risen half / three quarters of the way up.
All the air is in the top of the radiator again. So I have to prime again! I just syphon the coolant from the expansion chamber into my Wife's pyrex jug for microwaving peas, then pour it into the swirl pot again. There's no coolant loss.
All extremly odd!! Any thoughts? I have a new filler cap on order:
http://www.ebay.co.uk/itm/COOLANT-TANK-CAP-NEW-GOL...
and will let you know how I get on with that.
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