coolant tank not holding pressure...
Thread Starter
Audiworld Junior Member
Joined: Mar 2009
Posts: 40
Likes: 1
coolant tank not holding pressure...
'01 A6 2.7T
Been suffering coolant loss for some time. Recently it has been getting severe.
Still trying to rule out the need to replace the secondary water pump. How can I be sure that I need to replace it? What else should I consider? Would the need to replace the secondary pump cause my vehicle to run hot..which it never does..go figure?
I usually got a good amount of pressure when I loosened the coolant cap when it was sufficient warmed up, now not at all. Could this contribute to my recently extreme coolant loss? What could cause the coolant tank to not hold pressure anymore? Other than the danger of not having any coolant, are they any other risks?
Thanks to everybody that has helped me on this board before and in the future!!!
Been suffering coolant loss for some time. Recently it has been getting severe.
Still trying to rule out the need to replace the secondary water pump. How can I be sure that I need to replace it? What else should I consider? Would the need to replace the secondary pump cause my vehicle to run hot..which it never does..go figure?
I usually got a good amount of pressure when I loosened the coolant cap when it was sufficient warmed up, now not at all. Could this contribute to my recently extreme coolant loss? What could cause the coolant tank to not hold pressure anymore? Other than the danger of not having any coolant, are they any other risks?
Thanks to everybody that has helped me on this board before and in the future!!!
AudiWorld Super User
Joined: Dec 2003
Posts: 2,244
Likes: 3
From: Gardnerville, NV
The cap establishes the max coolant pressure, contains an over pressure relief valve. Any fluid exhausted thru this valve exits thru a hole in the bottom of the reservoir. Feel the underside below the cap, two square projections,fluid will drip from hole between them.
This lost fluid will run down thru the maze right, PS, of the engine. Coolant loss from a failing after run pump will run out the rear of the engine’s V and down onto the bell housing. Should be easy to determine from which area the fluid is coming.
This lost fluid will run down thru the maze right, PS, of the engine. Coolant loss from a failing after run pump will run out the rear of the engine’s V and down onto the bell housing. Should be easy to determine from which area the fluid is coming.
Thread Starter
Audiworld Junior Member
Joined: Mar 2009
Posts: 40
Likes: 1
Thank you for the response. Would a bad coolant cap ever cause the coolant to be purged completely from the tank? Prior to this past week, the coolant would sometimes stay at the same level and sometimes it purges completely. Being that the cap doesn't hold its pressure anymore, it seems as though it is happening much more frequently. Is there a connection, or am I just crazy.
Tech Guru
Joined: Oct 2002
Posts: 34,430
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Don't get too excited, the pump is much more likely to fail than the cap. A prolonged slow leaks leaves pink residue. If no residue near the cap, look elsewhere.
My money is on the pump. Better find that leak before something ruptures.
My money is on the pump. Better find that leak before something ruptures.
AudiWorld Super User
Joined: Dec 2003
Posts: 2,244
Likes: 3
From: Gardnerville, NV
Coolant residue would not be evident around a failed cap, inasmuch as it would leak out the bottom of the reservoir. But agree, pump seal, main or after run, more likely than cap.
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Tech Guru
Joined: Oct 2002
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Ideally, there should be very little pressure in the cooling system, but pressure does tend to accumulate. It's not the tank that "holds pressure", it's the system. If your system does not "hold pressure", there is a leak somewhere. A leak tester can pressurize the system and help locate the leak, but usually the pink coolant leaves a pink, chalky residue, even under the coolant bottle and on the frame rail if the cap is leaking.
The weak points of the system are the secondary coolant pump, which rarely runs, but it used to circulate coolant to the turbos in extreme heat shut off conditions, and the coolant tank. Look for the pink.
The weak points of the system are the secondary coolant pump, which rarely runs, but it used to circulate coolant to the turbos in extreme heat shut off conditions, and the coolant tank. Look for the pink.
No Bozos!
Joined: Mar 2002
Posts: 7,899
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From: Cowlesville, NY.... Pop 1,067
A bad pump or pump seal wouldn't cause the tank not to hold pressure, it would cause the system not to hold pressure.
On the topic of caps though. When I first bought my pressure tester I of course had to try it on a bunch of cars at the shop. I found MOST of the caps wouldn't hold full pressure. Nearly all of them held around 6-7lbs, but few held over 10lbs.
On the topic of caps though. When I first bought my pressure tester I of course had to try it on a bunch of cars at the shop. I found MOST of the caps wouldn't hold full pressure. Nearly all of them held around 6-7lbs, but few held over 10lbs.