Fizzing coming from expansion tank
Discussion
Gents,
I've just finished swapping out the coolant hoses and refilled the coolant with no dramas, but after running the engine up to hot and checking the fans and levels etc I noticed there was a faint fizzing wining sound coming from what I can only think is the pressure cap on my expansion tank.
The pressure cap was done up as tight as I could get it by hand and I replaced it last year as I was worried I was losing coolant through the old one at the time, so does anyone else think this isn't normal?
Has anyone else noticed this on their motors?
Could this just be the excess pressure slowly venting out after the engines been hot?
Ta
I've just finished swapping out the coolant hoses and refilled the coolant with no dramas, but after running the engine up to hot and checking the fans and levels etc I noticed there was a faint fizzing wining sound coming from what I can only think is the pressure cap on my expansion tank.
The pressure cap was done up as tight as I could get it by hand and I replaced it last year as I was worried I was losing coolant through the old one at the time, so does anyone else think this isn't normal?
Has anyone else noticed this on their motors?
Could this just be the excess pressure slowly venting out after the engines been hot?
Ta
Sounds like the cap is not sealing.
Remove it and clean both the rubber seal surface and the rim inside the tank neck.
Also many are not aware there is another seal in the cap which also needs to be cleaned/inspected.
Take the cap and turn it upside down. On the end of the spring is the main pressure seal about an inch in diameter. This needs to be cleaned and inspected for splits or perishing.
The second seal is under a steel or brass disc in the middle of the main seal. Lift the disc which is spring loaded and again clean/inspect. This second seal is there to let air back into the tank when the engine cools.
Steve
Remove it and clean both the rubber seal surface and the rim inside the tank neck.
Also many are not aware there is another seal in the cap which also needs to be cleaned/inspected.
Take the cap and turn it upside down. On the end of the spring is the main pressure seal about an inch in diameter. This needs to be cleaned and inspected for splits or perishing.
The second seal is under a steel or brass disc in the middle of the main seal. Lift the disc which is spring loaded and again clean/inspect. This second seal is there to let air back into the tank when the engine cools.
Steve
ClassicChimaera said:
The best way to expel air is using a container screwed into the top of the swirl pot and over filled slightly so when your running it up air can burp out. Have you done that. You can use a funnel if you can get it to seal.
I assume you have a hot Heater etc.
Top tip that Al, just done that when refilled the system, works a treat...I assume you have a hot Heater etc.
Pete
ClassicChimaera said:
The best way to expel air is using a container screwed into the top of the swirl pot and over filled slightly so when your running it up air can burp out. Have you done that. You can use a funnel if you can get it to seal.
I assume you have a hot Heater etc.
No I haven't done that yet, would you mind explaining that a tad more?I assume you have a hot Heater etc.
Chimaera27 said:
ClassicChimaera said:
The best way to expel air is using a container screwed into the top of the swirl pot and over filled slightly so when your running it up air can burp out. Have you done that. You can use a funnel if you can get it to seal.
I assume you have a hot Heater etc.
No I haven't done that yet, would you mind explaining that a tad more?I assume you have a hot Heater etc.
If you have a cold heater, make sure you have it on "hot", else it may mean you have an airlock in the heater (or a dodgy valve). I haven't had a problem with the heater, but you could release one of the heater hoses to try and bleed air out of it.
No doubt some other good ideas will be along shortly...
Pete
Chimaera27 said:
No I haven't done that yet, would you mind explaining that a tad more?
once you've replaced hoses you need to fill system.1 jack front of car up off the ground so helping the natural flow of water to the rear of the engine and heater matrix.
2 undo bleed screw in radiator
3 undo hose on the l/h side of the engine near the fuel rail.
4 set heater to fully hot
5 fill system via swirl pot. Keeping cap off the expansion tank.
Air should be expelled via the rad and the hose on the fuel rail, when water appears nip up.
The swirl pot should now be full.
You are now ready to start the engine.
Keep a container screwed or shoved into the swirl pot with 2 litre of coolant in it.
Start engine and as it warms squeeze rad hoses etc to assist burping, if more air comes out the coolant level will drop in the container slightly but not allow air back in. Keep the coolant level above the top of the swirl pot.
This last bit just gets rid of the last pockets of air filling the system can fail to do.
If I've missed anything I'm sure someone will be along to correct but that's basically it. Couple of years ago since I've done it so google it to be sure. Should be plenty of old threads on this.
Blue cap only!
Just read Toolbox200 post, don't run the engine to long as it will get hot quick.
Better to do as he says and run it for short periods and stop.
Edited by ClassicChimaera on Wednesday 1st March 18:43
ETA once you've done all this, run the car about (local)
When fully cooled release the bung in swirl pot and check water level.
It should stay full, on some cars it can settle about an inch from the top as mine sometimes does, I've topped it up via swirl pot before then noticed it pushed out into the expansion tank as the next time I've checked it cold, open swirl pot and it's say 10-15 mm from the top, fill it again and the same thing happens,, Once it's happy your coolant level should remain the same level in the expansion tank, about a quarter full.
The blue cap releases pressure etc so you need the correct one.
I've got a VAG replacement (blue) one. It works well.
For the life of me I can't find the link.
Edited by ClassicChimaera on Thursday 2nd March 09:45
Edited by ClassicChimaera on Thursday 2nd March 09:46
The only thing I'd add to the above process is....
Once you've satisfied yourself all the air pockets have been expelled make sure you've still got roughly a litre of coolant in your funnel. Gently raise the engine speed from idle to roughly 2,500rpm, you will see the litre of coolant in your funnel disappear down into the swirl pot as the now faster spinning water pump pulls the coolant around the system.
With an assistant holding the revs up you can now remove your now empty funnel and quickly screw in the brass plug, finger tight is fine at this stage.
Now let the engine slowly return to idle and properly tighten the brass plug.
The above final rev raising method ensures a solid column of coolant is circulating around the entire system and allows you to squeeze/trap in that vital last litre of coolant the system needs and is almost impossible to introduce without using the raised revs method.
Admittedly some of this disappearing extra litre of coolant will be filling your expansion tank, but I have found the rev raising method definitely helps the final bleeding process and gives better results than just screwing the swirl pot plug in at idle.
I have found using this method gives a much more effective heater in the winter and better management of engine temps in the summer, its also helped to give fewer 'fan on' periods and reduces the time the rad fans actually stay on, all of which indicates to me it's a worthwhile procedure.
NB: Once you've raised the revs, seen your funnel go empty, and removed the funnel.. you absolutely must get the swirl pot plug in before allowing the revs to return to idle.
If you don't get the plug back in and accidentally let the engine return to idle, you will have a massive steam cloud on your hands, this being that last litre of coolant you're trying to trap in the system puking straight back out and covering the hot exhaust manifolds.
An assistant holding the revs up for you definitely makes the procedure a lot easier
Once you've satisfied yourself all the air pockets have been expelled make sure you've still got roughly a litre of coolant in your funnel. Gently raise the engine speed from idle to roughly 2,500rpm, you will see the litre of coolant in your funnel disappear down into the swirl pot as the now faster spinning water pump pulls the coolant around the system.
With an assistant holding the revs up you can now remove your now empty funnel and quickly screw in the brass plug, finger tight is fine at this stage.
Now let the engine slowly return to idle and properly tighten the brass plug.
The above final rev raising method ensures a solid column of coolant is circulating around the entire system and allows you to squeeze/trap in that vital last litre of coolant the system needs and is almost impossible to introduce without using the raised revs method.
Admittedly some of this disappearing extra litre of coolant will be filling your expansion tank, but I have found the rev raising method definitely helps the final bleeding process and gives better results than just screwing the swirl pot plug in at idle.
I have found using this method gives a much more effective heater in the winter and better management of engine temps in the summer, its also helped to give fewer 'fan on' periods and reduces the time the rad fans actually stay on, all of which indicates to me it's a worthwhile procedure.
NB: Once you've raised the revs, seen your funnel go empty, and removed the funnel.. you absolutely must get the swirl pot plug in before allowing the revs to return to idle.
If you don't get the plug back in and accidentally let the engine return to idle, you will have a massive steam cloud on your hands, this being that last litre of coolant you're trying to trap in the system puking straight back out and covering the hot exhaust manifolds.
An assistant holding the revs up for you definitely makes the procedure a lot easier
Thank you all very much for the input, some really interesting advice there for next time I change the coolant.
It seems I may have been suckered by a cheap price tag when I went for a replacement pressure cap and bought a black one from ebay, looks as though it may be a fake hence it not working properly! I shall buy a new one from TVR Parts, unless anyone has a better suggestion for where to find one?
It seems I may have been suckered by a cheap price tag when I went for a replacement pressure cap and bought a black one from ebay, looks as though it may be a fake hence it not working properly! I shall buy a new one from TVR Parts, unless anyone has a better suggestion for where to find one?
Chimaera27 said:
Thank you all very much for the input, some really interesting advice there for next time I change the coolant.
It seems I may have been suckered by a cheap price tag when I went for a replacement pressure cap and bought a black one from ebay, looks as though it may be a fake hence it not working properly! I shall buy a new one from TVR Parts, unless anyone has a better suggestion for where to find one?
VW?It seems I may have been suckered by a cheap price tag when I went for a replacement pressure cap and bought a black one from ebay, looks as though it may be a fake hence it not working properly! I shall buy a new one from TVR Parts, unless anyone has a better suggestion for where to find one?
ChimpOnGas said:
The only thing I'd add to the above process is....
Once you've satisfied yourself all the air pockets have been expelled make sure you've still got roughly a litre of coolant in your funnel. Gently raise the engine speed from idle to roughly 2,500rpm, you will see the litre of coolant in your funnel disappear down into the swirl pot as the now faster spinning water pump pulls the coolant around the system.
With an assistant holding the revs up you can now remove your now empty funnel and quickly screw in the brass plug, finger tight is fine at this stage.
Now let the engine slowly return to idle and properly tighten the brass plug.
The above final rev raising method ensures a solid column of coolant is circulating around the entire system and allows you to squeeze/trap in that vital last litre of coolant the system needs and is almost impossible to introduce without using the raised revs method.
Admittedly some of this disappearing extra litre of coolant will be filling your expansion tank, but I have found the rev raising method definitely helps the final bleeding process and gives better results than just screwing the swirl pot plug in at idle.
I have found using this method gives a much more effective heater in the winter and better management of engine temps in the summer, its also helped to give fewer 'fan on' periods and reduces the time the rad fans actually stay on, all of which indicates to me it's a worthwhile procedure.
NB: Once you've raised the revs, seen your funnel go empty, and removed the funnel.. you absolutely must get the swirl pot plug in before allowing the revs to return to idle.
If you don't get the plug back in and accidentally let the engine return to idle, you will have a massive steam cloud on your hands, this being that last litre of coolant you're trying to trap in the system puking straight back out and covering the hot exhaust manifolds.
An assistant holding the revs up for you definitely makes the procedure a lot easier
Thanks for that. I have often wondered how you avoided the top hose draining when you removed the funnel/bottle from the swirl pot. As it is the highest point in the system it will naturally empty, always thought this was a duff piece of design and there must be a technique to keeping it full.Once you've satisfied yourself all the air pockets have been expelled make sure you've still got roughly a litre of coolant in your funnel. Gently raise the engine speed from idle to roughly 2,500rpm, you will see the litre of coolant in your funnel disappear down into the swirl pot as the now faster spinning water pump pulls the coolant around the system.
With an assistant holding the revs up you can now remove your now empty funnel and quickly screw in the brass plug, finger tight is fine at this stage.
Now let the engine slowly return to idle and properly tighten the brass plug.
The above final rev raising method ensures a solid column of coolant is circulating around the entire system and allows you to squeeze/trap in that vital last litre of coolant the system needs and is almost impossible to introduce without using the raised revs method.
Admittedly some of this disappearing extra litre of coolant will be filling your expansion tank, but I have found the rev raising method definitely helps the final bleeding process and gives better results than just screwing the swirl pot plug in at idle.
I have found using this method gives a much more effective heater in the winter and better management of engine temps in the summer, its also helped to give fewer 'fan on' periods and reduces the time the rad fans actually stay on, all of which indicates to me it's a worthwhile procedure.
NB: Once you've raised the revs, seen your funnel go empty, and removed the funnel.. you absolutely must get the swirl pot plug in before allowing the revs to return to idle.
If you don't get the plug back in and accidentally let the engine return to idle, you will have a massive steam cloud on your hands, this being that last litre of coolant you're trying to trap in the system puking straight back out and covering the hot exhaust manifolds.
An assistant holding the revs up for you definitely makes the procedure a lot easier
Genuine is about 20 squids form your local VAG dealer dont f
k about with cheap pattern ones be warned that the part number as been superseded many times 443121321 but this is one, there is also nothing wrong with the quality of these cap I have seen many fully functioning after 20 years +
k about with cheap pattern ones be warned that the part number as been superseded many times 443121321 but this is one, there is also nothing wrong with the quality of these cap I have seen many fully functioning after 20 years +Message Board | Chimaera | Top of Page | What's New | My Stuff