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Coolant Condensation Problems


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I had some coolant problems so brought it in and got a new coolant tank. After multiple trips to the shop it was still having some condensation issues. So after trying many things I messed up the first tank (learning experience) and had to get a new one. Well the same problem occurs. It is fine for short drives, but longer ones and the condensation builds up and is on the trunk lid. The shop claims they can never find anything but everytime I drive more than 10-15 miles it will happen. Coolant temp stays pretty even, but I think I found the problem tonight. Pictures are below - looks like some coolant is leaking from a small hole near the bleeder valve.

Anyone have any ideas on what the problem could be? This coolant tank is only 2 days old and this will be my 7 trip back to the shop in less than a month.

dsc00577smallgm0.jpg

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Has anyone check the tank cap?

Yes, the shop put on a brand new black cap with the tank. They said it was tested at 15 psi (i think that was it) while my old caps were only getting 8 and 15. I guess I could just buy another new cap from the dealer since that would be cheap.

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That hole is a drain so that can't be cause of the condensation.

Tighten the 8 screws for the bleed valve. Snug them up by hand. Do not crank on them or they will snap as they are so small.

haha yeah I learned that lesson last time when I did that and snapped a few of them. That is why I needed to get a new tank as I couldn't get them drilled out. But now that I have that tank I was able to take them out since my drill worked better with tank out. so now i have a almost brand new tank just in case it cracks again :-)

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That hole is a drain so that can't be cause of the condensation.

Tighten the 8 screws for the bleed valve. Snug them up by hand. Do not crank on them or they will snap as they are so small.

haha yeah I learned that lesson last time when I did that and snapped a few of them. That is why I needed to get a new tank as I couldn't get them drilled out. But now that I have that tank I was able to take them out since my drill worked better with tank out. so now i have a almost brand new tank just in case it cracks again :-)

Ok the bleeder valve bolts are on tight, but I still think the coolant is somehow leaking. I guess a trip to the dealer is in order since the shop that I went too seems to be pretty incompetent and has no idea (after 7 trips and 2 tanks on what to do and I dunno if they are even doing anything).

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There is a black cap on the market.

A local 996 owner ordered one from a dealer and he got a black cap. I thought it was aftermarket, but he said it came from a dealership.

My local dealer still has blue caps on the shelf. I had the parts guy look up the part number and it still ends in 01. Then I looked at the new cars in the showroom and they had the 01 blue cap. Don't know what is going on with the black cap. Maybe VW recently switched to black....

post-4-1183959537_thumb.jpg

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There is a black cap on the market.

Yep that is the exact cap I have.

What kind of lubricant should I use if I decide to try to replace the O-rings again? I am thinking the shop just installed the tank as they got it from the supplier without even bothering the lube them up.

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I guess a silicon grease. If you do it take pictures as I have not seen these O-rings. I have a January 1997 tank that I replaced. When I removed the bleed valve from the old tank there were no O-rings. But my car is so old I must have the first generation tank.

Strange that you still have condensation. I would ask a mechanic at the dealer but last time I did he said to tighten the screws as that was the most common cause of condensation.

You have a new cap that has been tested, You tightened the screws. I'm out of ideas.

post-4-1183965076_thumb.jpg

post-4-1183965092_thumb.jpg

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I guess a silicon grease. If you do it take pictures as I have not seen these O-rings. I have a January 1997 tank that I replaced. When I removed the bleed valve from the old tank there were no O-rings. But my car is so old I must have the first generation tank.

Strange that you still have condensation. I would ask a mechanic at the dealer but last time I did he said to tighten the screws as that was the most common cause of condensation.

You have a new cap that has been tested, You tightened the screws. I'm out of ideas.

Hm... that is the bleeder valve I have. But here are the instructions I was going from: http://www.ppbb.com/scgi-bin/boards/986/mu...es;read=1092331

Also the parts diagram over at pelican parts shows two o-rings in the bleeder valve cap.

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The black cap is not a Porsche cap, there is a possibility that the opening pressure of this cap a different value

has than the original Porsche cap ( lower )

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The black cap is not a Porsche cap, there is a possibility that the opening pressure of this cap a different value

has than the original Porsche cap ( lower )

What are the Porsche caps suppose to test at? The black cap was what the shop said they got from the dealership for their 996s and it tested at 15psi.

I guess it can't hurt to buy another blue cap at the dealership. More caps the better.

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Hm... now it seems that I can see vapor rising from the drain hole even after short drives. I felt a bit of fluid near the back of the bleeder valve, but couldnt see any anywhere else. Strange since it looks like there was a lot in the drain hole.

Its definitely time for a trip to the dealer. Now I just wonder how much this is going to cost. :o

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Some images and new information. Any and all help is great appreciated as always.

The drain whole steams when I stop after a 10 minute drive and it looks like there is fluid coming from the bottom of the bleeder valve area. Not sure if it was leaking down from the bleeder valve or just somewhere from there. Is it even possible for a tank to lank from there?

Also are all coolant reservoirs OEM? I am beginning to think the shop I went to used some aftermarket one since it has no Porsche markings or numbers on it anywhere and is from WorldPac (in San Jose, CA).

I think I will be taking it back to the same shop I have been going to since the problem is getting worse and worse after only 3 days and maybe 6 short trips of less than 10 minutes each on a new tank.

dsc00597kp5.jpg

dsc00596pc9.jpg

dsc00595yc4.jpg

Also strange. The coolant tank was made in April 2007, but has this bleeder valve on it:

imageupload58770888he2.jpg

Edited by olouie
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I've used only OEM coolant tanks on Porsche and never had a problem BUT have used WorldPack/Metrix coolant tanks on VW's and they turned out to be rubbish forcing me to buy the tanks from the VW dealer. I would return to the shop that did the work and get them to install a OEM style tank.

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After have 2 new coolant tanks installed by an incompetent shop I finally emailed Porsche_Joe over on PPBB about the write up he did a while back since I was confused. He was super nice and gave me some useful tips. So I did the procedure with his new information and took some pictures so everyone can share in how to solve the quite common coolant condensation on the inside of the trunk lid problem. ENJOY!

COOLANT BLEEDER VALVE O-RING REPLACEMENT PROCEDURE (from Porsche Joe)

Parts:

1 999-707-370-40 Rubber o-ring

1 999-707-371-40 Rubber o-ring

Tools:

Ratchet 1/4" Sears No. 43187

7mm socket 1/4" Sears No. 43503

3" extension 1/4" Sears No. 43539

Regular blade screwdriver

1. With the engine cold, remove the oil and coolant caps. IMPORTANT: The engine MUST BE COLD to prevent the possibility of scalding when removing the coolant cap.

2. Remove the plastic cover to access the bleeder valve. You can carefully pry up the cover using a regular screwdriver. You should see condensation on the underside of the cover and/or dried coolant around the bleeder valve. The bleeder valve is not the problem unless you have one or both of these symptoms.

3. Put the oil and coolant caps back in place. This is IMPORTANT because it prevents you from dropping a bolt or o-ring into one of the openings. That would be a bad thing!

4. Lift the metal ring of the bleeder valve from the horizontal position (closed) to the vertical position (opened).

bleedervalvebt0.png

5. Remove the 8 bolts that secure the bleeder valve to the bleeder valve housing and coolant tank. Lift the bleeder valve from the housing.

dsc00609jf1.jpg

6. Remove the bleeder valve housing by pulling straight up. This is a very tight fit. I had to use a regular screwdriver to carefully pry up the housing before I could remove it. Once you “break it loose” it lifts out easily.

dsc00603pk6.jpg

7. With the housing removed you will see the two o-rings on the top of the coolant tank. I sprayed some silicone lubricant on the new rings before installing them (yea, yea, yea, I know, silicone lubricant accelerates the deterioration of rubber but that’s what I had available at the time). The lubricant will help keep the rubber o-rings from sticking during assembly. Instead of silicone lubricant you could coat the new o-rings with a thin coat of liquid soap or even use something like Vinlyex. Remove the old o-rings and install the new ones.

Small O-Ring:

dsc00607im7.jpg

Large O-Ring (old one from “brand new tank” on left, real new OEM Porsche right)

dsc00605dz2.jpg

Both O-rings on the bleeder valve top

dsc00612yr2.jpg

8. Install the housing making sure the bolt holes line up properly.

9. With the bleeder valve still in the open position, install it on the housing.

10. Install the eight bolts (Hint: when starting a screw or bolt, use your fingers to turn it counterclockwise while gently pressing on it until you feel it “pop” into place then turn it clockwise to tighten it. If you do this each time you will never miss thread a screw or bolt again.) Be careful not to over tighten the bolts. I could not find torque specifications in the shop manual. If your problem continues then you may have to come back later and apply a little more torque.

dsc00613vn7.jpg

Be very careful here or this could happen to you and you will need a whole new tank if you break the bolts.

dsc00550ke8.jpg

11. Close the bleeder valve (move the ring from the vertical position to the horizontal position.)

dsc00614qx2.jpg

12. Remove the oil and coolant caps.

13. Install the plastic cover.

14. Install the oil and coolant caps being careful not to miss thread the coolant cap.

15. Go for a nice long test drive.

Random Pictures of Parts

Difference in ring size

dsc00608zo2.jpg

Top cap

dsc00548an9.jpg

Cap + valve base

dsc00601uf4.jpg

Dirty parts

dsc00606du6.jpg

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  • 1 year later...

Thanks for the write up. This is really helpful.

Two observations. Most likely the shop did use a non OEM coolant tank, but it probably didn't come with a bleeder valve. They used the bleeder valve from your old tank and tried to do the right thing by replacing the o-rings. Most likely, they pulled some generic o-rings out, which seemed to be the right size and used those. I think this was ultimately the cause of the problem. By switching back to the OEM o-rings, you solved it.

Another observation about this thread, in Tool Pant's earlier photo where he seems to have a simpler bleeder valve assy, I think he may have stopped one layer short of where you did, and thus, didn't encounter the o-rings.

I'm going to pull my bleeder valve apart this afternoon to see if I can find the source of a faint hissing/seeping air sound that happens when my 2003 Boxster S is hot. (also have a little condensation)

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Thanks for the write up. This is really helpful.

Two observations. Most likely the shop did use a non OEM coolant tank, but it probably didn't come with a bleeder valve. They used the bleeder valve from your old tank and tried to do the right thing by replacing the o-rings. Most likely, they pulled some generic o-rings out, which seemed to be the right size and used those. I think this was ultimately the cause of the problem. By switching back to the OEM o-rings, you solved it.

Another observation about this thread, in Tool Pant's earlier photo where he seems to have a simpler bleeder valve assy, I think he may have stopped one layer short of where you did, and thus, didn't encounter the o-rings.

I'm going to pull my bleeder valve apart this afternoon to see if I can find the source of a faint hissing/seeping air sound that happens when my 2003 Boxster S is hot. (also have a little condensation)

Roadracer:

When you pull the bleeder valve apart, be sure to check the large rubber diaphragm on the underside of the bleeder valve cap. It that diaphragm has a pinhole or if the diapragm rubber has "expanded" from constant exposure to the coolant over the years, it will leak or it will not seat and seal properly.

If that is the case, you can buy a completer bleeder valve assembly without having to replace the entire tank.

The most common cause of this condensation is the O-rings.

Regards, Maurice.

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  • 2 years later...

I had this condensation issue as well and late last year after buying a new coolant reservoir cap (didn't help) I swapped out the O-rings as well. This year I finally pulled the car out and I'm still getting some condensation, I took the bleeder apart again and realized I'd messed up a couple of the holes in the tank the 7mm bolts thread into and couldn't completely snug up two of the tiny bolts.. Would these bolts not able to be completely tight cause condensation to form? Should I just replace the coolant tank or should I try replacing the bleeder assembly first?

Thanks!

Edited by tawheed
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  • 2 months later...

I recently purchased a 2005 Boxster S that exhibits similar coolant condensation issue. Porsche dealer/service conducted a series of pressure tests against the cooling system with and without engine running, and could not find any presure loss. It replaced the coolant cap, but the problem persists. I am sending the car back to the dealer for 2nd round of diagnose. I will mention the bleeder o-ring to them. I will report back when the problem is fixed.

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I changed caps twice, current cap model# ends with "04." Still had condensation. So I bought bleeder valve assembly from PELICAN PARTS. Comes with 2 O-rings. Original valve only had 1 O-ring. Easy remove and replace. Be sure to follow instructions esp. putting a-freeze and oil caps back on before proceeding (they are removed at first step to allow removal of simple plastic plate that sits right below filler caps and oil dip stick) and be careful not to over tighten bleeder valve fasteners. A previous poster very helpfully posted the instructions, but these simple precautions bear repeating. Viola! No more condensation!

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  • 5 years later...

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