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YOUR RESEARCHCoolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Leading reported evidence
Replace coolant tank this winter along
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Performed · outcome unconfirmed · Original poster
So I was proactive and replaced the coolant tank this winter along with water pump and low temp thermostat.
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'Replace coolant tank this winter along' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check coolant level religiously and watch' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
I replaced the el cheapo tank with a genuine Porsche tank from Pelican and guess what - it now holds a vacuum.
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Test tank
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Performed · outcome unconfirmed · Original poster
I admit I vacuum tested the new tank before installing it and it was good.
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Use airlift
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Performed · outcome unconfirmed · Original poster
I use the airlift today to make sure there is not air in the coolant system and it will not hold a vacuum.
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Check coolant level religiously and watch
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Suggestion
In the meantime, check coolant level religiously and watch that temp gauge!
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Use airlift and creating a vacuum
No successful repair reported for this finding.
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Suggestion · Original poster
I can now trace the leak to the point where the pressure relief valve mates to the tank - you can hear the hissing after using the Airlift and creating a vacuum.
Coolant tank not holding vacuum - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
13 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
986Forum: 1 discussions
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1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
Unfortunately, since it is still not airtight, the coolant expands when hot and overflows.
So I was proactive and replaced the coolant tank this winter along with water pump and low temp thermostat. I use the airlift today to make sure there is not air in the coolant system and it will not hold a vacuum. I can get it to 25 psi vacuum but it drops to 0 in about 10 - 15 seconds.
My guess is the new tank has a leak - yes, I know, I went with a cheapo and not factory and am probably paying the price now.
What is the downside or risk with a tank that is not airtight? Does it need to be replaced immediately or can it wait? Is it just the nuisance coolant drip on the garage floor or something more drastic?
Thanks-
First, check to make sure that the tank is the cause - could easily be something else.
Whatever the cause, it should be repaired as soon as you can. In the meantime, check coolant level religiously and watch that temp gauge!
If the coolant light starts to slowly blink (even if the temp is ok), it means that the coolant level is low and needs to be topped up before bad things happen.
if you need to drive the car and the tank is the culprit, replace immediately. Don't mess around with the cooling system on these engines, it can cost you dearly.
The new tank may be perfectly fine. Check all the hose connections at the tank and make sure they are secure.
I know, stating the obvious but sometimes the obvoius is missed.
I understand the risk is low coolant introducing an air bubble that then creates a hot spot in the head that can result in cracking.
Are you sure the Airview system is sealing well at the tank neck? I had a small learning curve to getting the guage sealed at the neck. If so - put it under pressure and then check for leaks.
Put some UV dye in the coolant and pressurise the system. You should readily see where the coolant is leaking.
If you don't see an external leak, take out the spark plugs and and pressirise the system, then put a piece of hose in each spark plug hole and listen for a hiss. If you hear a hiss, my condolences, you have a serious problem with a cracked head.
I would check the o rings in the pressure release valve especially with the cheapo tanks they seem to always leak. I had the same problem on two after market tanks.
I checked the o rings in the pressure relief valve and the larger ring was bad - replaced it and the relief valve holds better than before but still leaks.
I can now trace the leak to the point where the pressure relief valve mates to the tank - you can hear the hissing after using the Airlift and creating a vacuum.
Unfortunately, since it is still not airtight, the coolant expands when hot and overflows. I have ordered a genuine Porsche OEM tank and learned a lesson to not cheap out on that part!
Whay a pain!
If you are sure its the bleed valve, I would try goobering the mating surfaces with something, silicone or JB weld to see if it will hold presuure. A lot easier than changing out the tank!
I replaced the el cheapo tank with a genuine Porsche tank from Pelican and guess what - it now holds a vacuum. I admit I vacuum tested the new tank before installing it and it was good.
The bad tank had aflaw in it by the overflow relief that kept it from ever sealing, the injection molded plastic did not travel to the far ends of the mold.
Lesson learned!
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