Coolant Tank Bleeder Valve

Good afternoon afternoon everybody this is my first post as this is my first Porsche. I got a bit of a fixer upper, but it runs, I�m having some issues with coolant tank. Place that I bought it from said they replaced water pump and coolant tank, the coolant tank keeps overflowing through the bleeder valve. Today I took the time and dumped all, but about a gallon of coolant out of the car And replaced. I followed the guideline that I found on this forum For purging the coolant system of air. Everything was going good until the thermostat opened and then coolant started squirting out of the purge valve continuously until I shut the engine off. Am I missing something here or is this �supposedly�new tanks leader valve faulty? Thanks in advance. I�m sure they�ll be many more questions to come. I am handy with tools and have worked on other vehicles, but never a 911. 2001 911 Carrera 84,000 on body, 13,000 miles on a replaced motor, unfortunately I don�t have any information on the engine i.e. how many miles I had on it or if it was refurbished.

Did you buy this car from a place that specializes in selling used cars? Those guys are notorious for using the cheapest parts possible to maximize their ROI. The aftermarket coolant tanks are crap compared to the Porsche branded ones. You can bring the car back to them and see if they take a look at the malfunctioning coolant tank, or you can replace it yourself on your own dime. But this scenario leads me to wonder about the rest of the car... maybe there are other surprises lurking within and it could get expensive really fast.

What "bleeder valve" are you referring to? Maybe a picture would help. Are you talking about the black valve on top of the coolant tank? Or the cap where you add coolant to the expansion tank? Like all modern cooling systems, it is a closed pressurized system.

Black screwed on cap with the triangular tab, and yes, I’m sure there will be plenty more surprises. This vehicle was on consignment. but I got it cheap knowing I’d have to fix stuff. I know the coolant system can be finicky on these cars due to air pockets. I bought an air VAC tool, but I couldn’t get it to bring up the pressure because I believe there was too much residual coolant in the system. So I decided to use the method that I found on here instead. Which I’ve used similar methods in other vehicles, and it worked fine. I’m sure the tank is an Amazon special, and I was going to buy an OEM tank but decided to try this first thinking maybe there was just too much air in the system but now I’m not sure. Thank you for your replies

Looks like the bleeder valve is old, but you have the newer cap ending in 04. Perhaps they just replaced the expansion tank and cap, but used the old bleeder valve. Here is a parts diagram. I see the bleeder valve has a part number, but I don't know about availability of getting just that. Hold onto your wallet. Sounds like you have a lot coming up $$$. https://www.autoatlanta.com/porsche-...section=105-20

Did you fill the reservoir, leaving the cap off, start the car, turn up the heat, let it get it hot filling it as the level drops?

Since most cars don�t have a �bleeder valve� and this is your first exposure to one, I can see where the confusion is coming from. Where the coolant is in your photo, near the wire bit on the black coolant valve, I can tell you the valve is faulty. No coolant should come out of the bleeder at any time. The bleeder has a diaphragm that opens when the system pressurizes and allows communication/bypass between the reservoir tank and circulating portion of the coolant system, so it can burp any air back into the reservoir. Would guess the diaphragm is bad since coolant would have to get around it to come out of the top. The two parts of the valves seal to the tank with a set of o-rings, one radial and one face, and are held on with all those screws. You can get a cheap URO bleeder valve from RockAuto, and it may be possible to get an OE one from the dealer. I have a Uro one as mine was leaking from the lower o-ring after what was probably a small leak corroded the screws out. The URO part is working ok, although I can�t speak to the longevity of the diaphragm vs OE, but it looks and functions fine. In my case it will be replaced sooner than later as the old screws made a mess of the reservoir, but I�m glad to be back on the road for a few bucks to find out what else I needed. I�m also rehabbing a well enjoyed car.

FYI I did swap the bleeder cap with the tank in the car. With the 10mm nut that also holds the SAI pump off (and maybe another mount screw? Can�t recall, Pelican has a guide) I slid the tank from its bracket and maneuvered it forward enough to pull all the screws that hold that valve on with the tank in the car and still connected. I used a 1/4� ratchet and driver. Wasn�t terrible.

Yes, I followed the write up I found on this forum

Thanks for the info, I think I’m gonna start with putting a new bleeder valve assembly and see what happens. Last thing I want to do is drain all the coolant again nd replace the tank.

I think that’s my plan for now

Another pic in action

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This is what I'd do.... Highest points in the cooling system where air gets trapped, is vented thru vent lines from the radiators top vent hoses and the oil cooler vent hose. These vent lines are connected to reservoir 2 chambers surrounding and directly below the vent valve. These chambers are closed off to tank till the vent valve senses 8psi , then it opens internally to vent from these inner chambers air back into the reservoir. Then the reservoir cap vents excess air to atmosphere at 18psi. With vent valve bail open/up, valve is always venting internally at a low psi any air back into the reservoir tank leaving the bottom chambers below vent valve open to the tank. At no time should any coolant leak out of the top of vent valve, as you know. Vent valve operates all internal in the tank, no air vents out the top of valve ever. If it is leaking coolant then either an o-ring is pinched, not seated correcly or busted , or diaphragm is ripped or not seated correctly and allowing coolant to escape the top of valve. Or the plastic body of valve is cracked. If it were me, I'd leave all the coolant in system and pressure test system to 15psi or so. Then using dish soap suds on top of valve I'd see exactly where its leaking. If the plastic is cracked/leaking, new valve is needed. If the leak is coming out where valve seats on tank, then its time to take it apart, clean everything up good, check all orings carefully, lube orings with little grease and reassemble carefully/evenly tightening all bolts a little at a time in a cross star pattern. If leak is coming from top of tank valve/bail plunger, then the diaphragm is the problem. Could be ripped or not seated correctly. Same exercise, take apart, inspect, clean carefully, seat all o-rings/diaphragm correctly after being lube'd and reassemble, pressure test. Don't over tighten bolts, they just need to be snug, sealing is done by keeping o-rings & diaphragm seated in the correct place. jmho

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Awesome information, I can already tell I’m in the right place. Thanks a lot, I may try taking it apart and see if I can see something wrong with it from when it was assembled. It’s supposed to be new, but I’m having my doubts now. Thanks again

Here’s the valve, no way that coolant tank was replaced.

Pelican parts came in clutch, new valve will be here tomorrow.

I replaced the valve with a new one. There is no more coolant escaping once the engine reaches normal operating temperature. So I let it idle a bit longer and decided to take it for a drive but I didn�t get very far before the engine started heating up quickly. By the time I got back to my house probably less than two minutes, the temperature was already almost maxed, and the coolant had dropped about two or 3 inches in the tank. So I think I still have Air trapped somewhere. Or at least I hope that�s what it is.

Did you change the thermostat? The water pump? Sorry I don't remember and I am too lazy to go back to read everything...

I was told the water pump was replaced from a ppi. And that�s what the dealer told me as well. But the dealer also told me they replaced the coolant tank, which I have my doubts about that, unless they ordered a new tank and transferred the pressure valve and cap over from the old tank? I can only assume the t stat was replaced at that time as well with the water pump. Also the backstory is the dealer was selling the car for somebody on consignment. Their mechanics told the seller they thought it had a bad head gasket, which allowed me to get it at a much lower price than other 911s. But I don�t think it�s a bad head gasket. I don�t think they burped the system properly on top of having a bad pressure cap that made it look like a bad head gasket. I talked to a tech at A Porsche shop here where I live and he said out of the hundreds of 996�s he�s seen in the past, he�s never seen a blown head gasket. So I took the chance.

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Take a photo of the water pump and thermostat. If new, then they should have a different colour. Let us see. The elephant in the room is the head gasket. There are tests that test the coolant from the blue cap and can tell you if you have fumes/gases in the coolant. Find such a test and test your car, since you have this indication. https://www.ebay.com/itm/358271591271

I�ll do that, and I have an exhaust fume test kit that I can do. I just haven�t done it yet.

At what times should have the metal ring in the up (open) position? While driving or just while I�m trying to purge the air in the garage.

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Open bail (up) and run through several heating/cooling cycles, keep a jug of coolant mix with you in the car in case it needs topping up.

The ring will rise when pressurized� someone in here said 8 psi. That sounds reasonable from playing with pressure testing. I didn�t want to hurt my car or make a mess test driving to find leaks so I bought a coolant pressure test kit. It was only $60 on Amazon, with a few caps and a pump. The bail on the overpressure did lift, and was insightful in how the system is intended to function. Don�t exceed about 18psi pressure testing, it�s not necessary. I set mine to 20 based on the 21psi cap, and both rads leaked a bit overnight. Now I have new CSF rads in the garage I haven�t installed but the old rads haven�t leaked at all in 300 miles of driving. Surely the replacements will be nice, but the leak was the result of my hamfistedness and not an immediate need. Maybe it will see 20 psi hot and on track, but it�s a poor cold test point. The manual says not to exceed the lower value 16 or 18psi iirc. There is a lot of info on here about vacuum bleeding to fill coolant, you can get a kit to help do both. Without vacuum bleeding, you could precharge the pressure cold so the valve opens, then start the car to burp air without having to get it full hot, then shut it down as the coolant level drops and before the car overheats. While head gaskets are uncommon, head cracks do occur, and would have the same air/exhaust in coolant result. A coolant pressure gauge would show you that too. In the near term, refilling and another lap around the block, rinse and repeat, is probably reasonable. If you have a lot of white smoke, that could be where the coolant is going. The wise guys at Porsche also put the coolant reservoir drip line on the drivers exhaust, so you may not find coolant on the ground if it�s evaporating. My drivers exhaust is notably rustier than the passenger side, the long slow leak may have been the culprit (or just 190k miles and a bit of salt).

Ok, thanks. That’s pretty much what I’ve been doing

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1) lets start from scratch and make sure whats really going on here. First, Check your oil for a milkshake on the dipstick, if oil is pure, continue on from here. Warm engine to full normal operating temp. Immediately Park car on level surface preferably in garage over night without taking off the coolant cap. You can let it warm up without driving it if you want, if you do drive don't go far. Car must be level. If engine was already cold/cool before you started it, fill reservoir first, to half way between full and low marks, do not over fill. You can leave cap off when its warming up and check if any combustion bubbles/pressure is forming in the tank as it warms up. Once its warm and t-stat opens there will be some flow/expansion in the tank so get cap back on before its fully hot. You can use distilled water, as depending how this all turns out, might have to dump all the coolant for a repair. That will be determined once we get all air out and the coolant to the correct level and see how it does... As the engine cools it pulls in needed coolant from reservoir into the engine, if you take off the cap when hot/warm you'll break the needed vacuum/pressure for cooling system to do this. Engine must get too stone cold to finish suking in all the coolant it needs. Can't rush this procedure. Might have to do this operation a couple of times to get all the air out and correct level of half way between full and low. Keep the vent valve bail in the up position, do not put it down till this whole thing is done. I run my car with it up all the time. Once you get all air out and coolant at the correct level when cold in the morning, run car easy and close to home till up to temp. See how it does. If it still overheats/starts spiting out coolant, obviously thats a problem. If gauge goes over line between 180 and 250 thats to high. Then its time to start checking the rest of cooling system. I'd do the simplest things first, like check radiators for being plugged with leaves/debris. Then move on to the T-stat /water pump... Head gaskets are 1 of the very few things that don''t seem to ever be a m96 problem, so it would be rare to see yours blown, very rare. Water pumps on the other hand frequently bust off their plastic impeller blades and then don't pump/flow/cool good. On the 996.1 the broken blades clog up the heads coolant systems passage ways causing head hot spots/head cracks. T-stat could be stuck closed, but thats a long shot... Anyhow, thats what I'd do at this point... jmo

Thank you for the thorough reply. The oil looks normal and there are no visual leaks anywhere now that I�ve replaced the valve on top of the coolant tank. There is no smoke coming out of the exhaust on startup or while idling. But I I believe I�ve been doing this cycle wrong. so basically last night would�ve been the first night. I did it right I guess. I drove it to it got hot. I left the cap on it and parked it, but it was not on a level spot so tonight I�ll make sure I do that. So I will try this method starting tonight. I will also check to see if the water pump is actually new like I was told. I have left the valve open for the last two days. I don�t know if it tells you one thing or another but last night I let it I�ll read it a revving a few times to get it up to temperature until the fan kicked on and decided to drive it. Literally within 1-2 minutes of that the temperature rose to almost 250 I immediately turned around and parked. There was no steam or any indication that the engine had overheated at that point, thank goodness. But there was a lot of noise in the coolant tank. Thanks again. also, I forgot to mention that I did clean all the debris in front of the radiators when I removed the front bumper

I don't know if you have done the procedure of warming the car up with the cap off and waiting to see the level drop and refilling but this is a key part of all this.

I did do that initially, but don’t know if I did it right

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Well, if you're sure the coolant level was correct and no trapped air and still run up to 250�, obviously you've got a problem. My question before diving in further, make sure system is half way between full and low in the morning before cold start after a proper heat/cool cycle. Did you have to add coolant before last cold start..?

Thank you for the reply, the funny thing is I did buy a vacuum bleeding kit, but when I tried to use it I found the pressure valve was leaking assuming I was doing it wrong, I went ahead and filled the coolant system up with coolant and decided to do it the other way, and then, of course, I realized the pressure bill was still leaking nd was faulty all the help I received so far in this post. So now that’s changed out. I’ve got no coolant leaking anywhere. Just the overheating issue.

I’m not sure that all the air is out, actually I’m pretty sure it’s not at this point. I will just keep cycling it and see what happens and I will pay more attention to the level i.e. between max and minimum marks before cold start. Thank you

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Sorry the posts are getting all jumbled up. I’m still learning how to post on here lol.

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You mentioned you warm it up till the fans come on. If you mean fans on high speed, thats very hot. Keep a/c on cool, on slowest fan setting, and radiator fans should always be on low speed as soon as car is started. No need to get it so hot (220�F+) the high speed fans come on, at least till you've got your overheat fixed...

With the leak fixed you should try the vacuum bleeder again, with the bail up.

Update, I pressure tested before I drove it, I was able to get just about 10 pounds of pressure on it before it started squirting out of the bleeder hose on my vacuum, that held the pressure until I pulled up the tab on the valve. I topped off the tank in between minimum and maximum drove it for 15 minutes around my neighborhood staying in second gear trying to keep the RPMs high and low and the temp never exceeded 190, I pulled back in the garage and tank was empty. When I woke up this morning. Some coolant had floated back into the coolant reservoir so I topped it off again and will give it another longer drive tonight. It looks like maybe I’ve got this figured out finally. Thanks for all the help. I’m sure I’ll have more questions in different areas as this journey continues.