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Coolant air bubble?

bglz42

By bglz42
in 986 Series (Boxster, Boxster S)

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bglz42 Member

bglz42

Posted
Posted

Air bubble?

Several weeks ago, I incurred a self inflicted wound… after checking the fluid level in the coolant tank, I crossthreaded the cap (new 04 cap). Car did not overheat, but lost some coolant. After reading lots of posts on the subject, I added distilled water, (1/2 gallon), popped up the bleeder and performed the procedure outlined by Pelicanparts. Afterwards, started driving it around with bleeder open to release any air. So far so good. No overheat, no additional loss of coolant.

My question revolves around the behavior of the coolant tank afterwards. After driving, I can smell antifreeze. Nothing on garage floor. When I pop the trunk, the underside of the compartment is very wet from condensate. (There was always a little, now a lot…) The bleeder valve is fully extended. When I let it cool down the bleed valve retracts, but there is a ton of pressure in the tank. When I unscrew the cap, I loose about a cup of fluid to the drain.

The coolant is in good shape, looks good smells good. I plan on a full flush, along with trans service and plug change at my indie, but because of my schedule the appointment is a few weeks out. First: Is there an issue?

Second: Is there a DIY fix without a full drain if there is an air bubble?

I'd like to be able to use the car in the meanwhile...

Thanks!!!

Jim

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JFP in PA Member

JFP in PA

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The easiest way to get this under control is going to be lowering the coolant level in the tank to about midway when the car is cold and then using a vacuum filling tool to pull the air out. Once the system is at full vacuum, you can then use it ability to pull in any of the excess mix you removed to correct the coolant level.

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  • 7 months later...
bglz42 Member

bglz42

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I am still fighting this issue. Bought a UView. Vacuumed it and refilled it. Rebult the bleeder. 04 Cap. Never overheats but lots of condensation under the trunk lid. Drove it on the freeway for 100 miles in the heat yesterday. As I returned to my driveway the light started blinking. Temp normal. After cooled, I removed the cap. Lots of pressure and level came up a lot. Added about a quart of coolant. Not sure where to go from here...

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JFP in PA Member

JFP in PA

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I am still fighting this issue. Bought a UView. Vacuumed it and refilled it. Rebult the bleeder. 04 Cap. Never overheats but lots of condensation under the trunk lid. Drove it on the freeway for 100 miles in the heat yesterday. As I returned to my driveway the light started blinking. Temp normal. After cooled, I removed the cap. Lots of pressure and level came up a lot. Added about a quart of coolant. Not sure where to go from here...

 

Try pressure testing the system at the tank, we occasionally find tanks with small cracks that lead to condensation in the trunk area.  If the system is closed and tight, there should be no condensation.

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kbrandsma Member

kbrandsma

Posted
Posted (edited)

It is not uncommon to have a faulty bleeder valve.  Part number 996.106.347.02.   Fits 986, early Cayman and some Carrera's.  Cayman photo shown.  You would need the entire kit, comes with 8 hexagon-head bolts (part #3 in photo). 

 

Word of caution these bolts strip easily so don't over tighten. The bolts don't strip the plastic they screw in to does.  Priced recently at Sunset for about $75.  Easy DIY.

 

BleederValve_zps3c93454e.jpg

Edited by kbrandsma
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Hilux2400 Member

Hilux2400

Posted
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post-86549-0-34348300-1362506598_thumb.j
post-86549-0-80543500-1361289081_thumb.j

I was having coolant loss before replacing my header tank. It was leaking from the gasket between the relief valve housing and the tank as one of the screws had corroded. I did a temporary fix with a new screw from a second hand tank.  I replaced the tank with a new one and I was still having leaks until I put a new tank cap on.    

 

When the car is up to temp and the coolant level seems down it is because of the pressure in the header tank. If you remove the cap at this time the level will rise and possibly overflow.

 

You should only check levels and fill when the car is cold.  Try and do it with the front pointing downhill as you get a better chance of air bubbles rising to an outlet. Also when you check levels always do it with the car in the same position each time.        

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kbrandsma Member

kbrandsma

Posted
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Is it possible the cross threading of your coolant cap may have damaged the coolant cap or the threads of the tank?

 

If you have a UView AIrlift  tool you can check the system to see if it holds a vacuum over a period of time.

 

550000.jpg

Edited by kbrandsma
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bglz42 Member

bglz42

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It did not appear to.

 

I carefully inspected the cap. It looks good.

 

I just took for a test drive. Still some condensation and a little wispy steam. The bleeder valve is fully extended. Temp normal. I am beginning to suspect the cap.

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Ahsai Member

Ahsai

Posted
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There is a male to male adaptor you can buy to pressure test the cap but the cap is not expensive so you may as well buy a new cap. I also like kbrandsma's theory about damaged threads. I guess worst is to replace the whole tank and the cap.

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Hilux2400 Member

Hilux2400

Posted
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From memory, down when cold and up when hot and under pressure, or up when I lock it in position with the clip in a vertical plane.

 

I think the comments about the cap are correct as I was losing coolant before I replaced mine.  It looked OK, but wasn't sealing.  They are not expensive and I think they are VW Golf caps from about 1988. 

 

H

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  • 1 month later...
bglz42 Member

bglz42

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I am still struggling to understand how this cooling system is supposed to work... 

 

If you read my original post, the symptoms are still the same. Condensation under the lid, and the bleeder valve extended when hot. Never overheats.  Is this normal?

 

I have:

Bought another 04 cap, (Actually I am on my third cap, thought maybe I was getting bad ones...)

Evacuated the system using an Airlift, held pressure just fine.

Wrapped the filler neck in teflon tape.

 

Just yesterday, I lost some coolant when I removed the cap. Car was cold, and had been sitting for a week. About a halfcup of fluid came out under pressure. (Probably overfilled slightly.) I cleaned up the mess, applied teflon tape to the neck and re-installed the latest cap. Ran it for about 15 miles, and pulled back into the barn. I could hear a very slight hiss. I squirted soapy water onto and around the bleeder valve to see if there was a leak, and saw no bubbling. The hiss appears to come from the cap itself venting. Is it supposed to vent off the extra pressure? The bleeder valve WAS extended. Temp normal.

 

 

I am taking the car to Boxstoberfest in two weeks, and it will get wrung out pretty good. I am a little nervous about it...

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Ahsai Member

Ahsai

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The CAP is supposed to vent off extra pressure only when the pressure is very high at 27-29 PSI or so. Have you ever pressure test the tank with a proper tester that can pressurize the tank to something close to 19PSI? The vacuum tool is not an effetive leak tester. Some leaks only reveal themselves under positive pressure and not vacuum.

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JFP in PA Member

JFP in PA

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No I have not done that... are you thinking that it's leaking?

 

 

Just about anything can leak, even brand new parts just out of the box.  I would be pressure testing the system and the cap with something like a Stant pressure test unit:

 

SNN-12270_OH_xl.jpg

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