How can air get into the cooling system?
Discussion
Approx 170 mile run completed 2 weeks ago, and the following day when engine was stone cold had water coming out the top of the expansion tank when I released the cap to check the level.
AA came and suspected airlock, however he did also conduct a sniffer test for exhaust gases which was negative (head gaskets were fully repaired 2 years ago when diagnosed as faulty).
Airlock released last week and no more obvious signs or issues, however few miles completed since then and when checked tonight water was back to approx 3/4 up the expansion tank.
Any ideas where to start looking now? Appreciate any thoughts.
AA came and suspected airlock, however he did also conduct a sniffer test for exhaust gases which was negative (head gaskets were fully repaired 2 years ago when diagnosed as faulty).
Airlock released last week and no more obvious signs or issues, however few miles completed since then and when checked tonight water was back to approx 3/4 up the expansion tank.
Any ideas where to start looking now? Appreciate any thoughts.
Thanks for all the replies.
As mentioned system professionally bled and set up last week so I have no doubt it was done correctly.
Hoses must be at least 6 years (and probably a few years more) so could be a good place to start.
Rad also showing slight signs of breaking down / wear but as mentioned no signs of obvious leaks. Am reluctant to start changing bits in the hope of sorting it and would rather have a clear steer first.
As mentioned system professionally bled and set up last week so I have no doubt it was done correctly.
Hoses must be at least 6 years (and probably a few years more) so could be a good place to start.
Rad also showing slight signs of breaking down / wear but as mentioned no signs of obvious leaks. Am reluctant to start changing bits in the hope of sorting it and would rather have a clear steer first.
As an update on this -
New rad was installed approx 6 weeks ago, and all seemed ok. Having monitored the water level in the expansion tank for the next couple of weeks it seemed to settle at about 0.5 inches below halfway - all seemed good, car was running cooler (approx 80 degrees), fans kicking in at around 83 degrees.
However, after a run of approx 90 miles the weekend before last which involved higher speed and higher average revs, water level in the expansion tank had risen back up to approx 1.5 inches from the top of the expansion tank when checked on a cold engine. Small release of pressure / bubbling as well when the cap was released.
Now having consulted mechanic, and before he starts taking the engine apart, are there any other areas to perhaps focus on?
To summarise -
Head gaskets repaired 2 years ago.
New rad just fitted, system bled and checked.
Higher miles / higher speeds / higher revs appear to cause rising water in the expansion tank.
I'm trying to stay positive and realise that this is very basic info given here - just have the feeling that this is not going to be easy or a quick fix.
Appreciate any possible ideas.
Thanks
New rad was installed approx 6 weeks ago, and all seemed ok. Having monitored the water level in the expansion tank for the next couple of weeks it seemed to settle at about 0.5 inches below halfway - all seemed good, car was running cooler (approx 80 degrees), fans kicking in at around 83 degrees.
However, after a run of approx 90 miles the weekend before last which involved higher speed and higher average revs, water level in the expansion tank had risen back up to approx 1.5 inches from the top of the expansion tank when checked on a cold engine. Small release of pressure / bubbling as well when the cap was released.
Now having consulted mechanic, and before he starts taking the engine apart, are there any other areas to perhaps focus on?
To summarise -
Head gaskets repaired 2 years ago.
New rad just fitted, system bled and checked.
Higher miles / higher speeds / higher revs appear to cause rising water in the expansion tank.
I'm trying to stay positive and realise that this is very basic info given here - just have the feeling that this is not going to be easy or a quick fix.
Appreciate any possible ideas.
Thanks
V8 GRF said:
Has the heater been open during this process?
If the system is filled and bled with the heater off then when you switch the heater on there is often air trapped in the heater pipes that then needs to be removed.
It has unfortunately - system was filled on hot. Has been set to hot and cold since the issue started again with no difference, ie water risen in the expansion tank.If the system is filled and bled with the heater off then when you switch the heater on there is often air trapped in the heater pipes that then needs to be removed.
Seemed to be fine for a few weeks on journeys to work and back that are A and B roads with a total of approx 40 miles, but does seem to be the higher mileage journeys with higher speeds and engine revs that highlight this problem. Reluctant to take engine apart due to likely final cost but looking increasingly likely that it may have to be done.
hififreak said:
i had, let's say so, the same Problem after my small accident....
no CO was measured in the swirlpot...but nevertheless -> head gaskets caused it!!
solution: surface grinding of the heads, new gaskets....done!
it was MINIMAL leakage and just hairline crack from combustion chamber to coolant ...
and the best way to fill swirlpot to about max was always mentioned -> take off the hose on the top of the left cylinder head..that is the TOP of the coolant System!!
Heads machined flat and gaskets done 2 years ago - so possible I guess, but unlikely? I'm assumimng something else and, thinking negatively, something major!!no CO was measured in the swirlpot...but nevertheless -> head gaskets caused it!!
solution: surface grinding of the heads, new gaskets....done!
it was MINIMAL leakage and just hairline crack from combustion chamber to coolant ...
and the best way to fill swirlpot to about max was always mentioned -> take off the hose on the top of the left cylinder head..that is the TOP of the coolant System!!
ETA Just reading the details of this thread closely. Why do you suspect air in the system,is the car overheating? Filling up the expansion tank without leaking can just be simple overfilling?
Edited by V8 GRF on Tuesday 24th June 15:08
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No signs of overheating, car behaving normally. Just that water level in the expansion tank is rising when engine is stone cold so assuming that it's being pressured somehow forcing the water to rise.
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