coolant refill the old fashion way... too much overflow

'04 C4S 6MT I looked at previous thread regarding this but could not find a good explanation. If you've seen the other thread i had recently replaced my thermo stat to a 160F and a new water pump. I purge the system with shop air at 10PSI to rid of the original 6 gallon in the system. Unfortunately i think i have a leak on my expansion tank therefore i could not use the vacuum fill system. I will have to save the tank replacement some other time. I currently have the car jacked on the rear. I have the bleeder valve on up position. I fill the tank as much as i can making sure it is just at the minimum line before i turned the engine on. Heater on max. Every time the coolant temp goes above 180F there is large amount of overflow from the expansion tank spilling quite a bit of coolant on the ground. Is this expected? I have to turn off the engine to stop the burping. I am thinking there is quite a bit of air in the system. Do i just turn engine off to cool down each time it goes above 180F and repeat filling process? Should I just maybe have the car on a flat level?

I've read that a guy here simply burped his system with out the vacuum process. I've got mine apart now and plan to use that method. What you describe is not that unusual on regular cars. I would keep filling until the radiator was full . However, these cars are different. How much coolant did you take out? all 6 gallons? That's a lot of burping to do. How much coolant can you get in between each burp?

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6 gallons out. I was only on the 3rd gallon before it started spewing things out. Yup a lot of burping. A month old baby. I did try the vacuum process using my brand new Maddox kit but it could not hold negative pressure. Likely a bad expansion tank as it is the original i believe. Have 103K+ on the odo.

If you have a leak, the vacuum fill tool will not work. You MUST fix the leak, ( whether you use the vacuum fill tool or not). Never drive with a known leak. Since you have the ability to pressurize the system, you can use pressure to find the leak and also partially fill the system. You can apply up to 19psi pressure on the system, if the leak is down low it should be evident and coolant will exit the leak if under 19psi. IF the leak is high up (coolant tank), the system will keep purging air and accepting coolant untill the coolant level reaches the level of the leak, then you will have visible evidence of where the leak is...

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I understand I have to fix the leak. Which i will. I returned the Maddox kit since I could not use it. I have the air compressor but now i don't have the adapter to seal the coolant tank. Will have to run out to autozone and get one of their loaner tool for pressure testing. If it is indeed the expansion tank then i have to order it first. In the mean time I want to try to fill the system manually. Just this constant spewing is annoying. My thermostat is a Wahler rated at 160F. During the filling process the temp stays at around two-three marks above 180 is this because I don't have enough coolant in the system? Or a defective thermostat? Seems obvious but asking anyway. I touched the hoses that go to pump and thermostat -- both warm so coolant is flowing there. I feel heat blowing through the fan now after I lowered the car on level ground. I have not noticed any obvious leak under the car. No obvious leak around the new pump and thermostat. I made sure the engine surface was clean prior to applying the new gaskets/pump/stat.

R u running the car with the cap off? If so its gonna dump fluid. To burp the system just pull the metal wire tab to the vertical position. This will keep the vent to the over flow tube open. I have filled the system several times this way. may take a dozen drive cycles. Also a few if use have had issue with the wahler t-stat and we all switched to the ln-e unit. Keep an eye on your temps

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got the cap off the whole time and the metal tab on up position.

Yea put the cap it will solve your issue.

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That is probably the problem. The cap should be on with the metal tab in the up position. That's what I'll be doing. The vent out the top will allow it to burp. Once it chugs with the thermostat opens up you can take the cap off and fill.

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aahhhh! i been looking at some burping DYI and they all say keep cap off. thank you.

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yup will try this.

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Most systems dont have a pressure release valve like ours or rads in the front. Lots of dips and vallies in the system for air to hide.

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well that helped also what it needed was a drive around town to get the fluids moving around and air to ride up to burp. No longer having issue w/ overflowing. I think i have about 4 gallons + in so far. Two more to go throughout the week. Again haven't noticed any drips at the bottom. So likely i have some leak on the expansion tank. Should had added that on my task to begin with. Oh well. Rented coolant pressure test kit from O'reilly but it didn't fit the tank opening. May have to rent the adapter kit tomorrow. This past week had been an ordeal but at least now I know how to remove broken bolts and much more confident in working with this car. So safe to have the burp valve up for a while? Since the new stat is rated for 160F should the coolant temp gauge show 160 instead of 180? Thank you for all that had been helpful and provided words of encouragement.

The thermostat just begins to open at 160, it still has the same operating temp. Yes, you can drive it around with the burp valve open.

No it will still equalize at the same temp but it wil take longer to get there. Your rads r only so efficient and the fans dont turn on till 208*. yes u can keep the valve open. Minus 2 gal is a lot so travel with the fluid in case it burps and drops quickly.

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Got it!

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Whoop, got it! yup will have two gallons on hand.

This is my baby after correcting the paint and polished w/ a DA polisher.

So tonight is 55F outside and with the heater off I decided to drive out to get something from the gas station. Come back to my idling car and noticed a bellow of steam coming from the engine bay and coolant smell in the air. Opened up the rear and noticed coolant had gurgled up around the coolant cap. The cap remained tight in its position. The metal vent wire remained in the up position as I had done so since beginning of this week. Odd thing is I had a spirited drive for two hours the other day and did not get any overflow. It is not overfill as I approximately have about 1.5 gallons left to put in. I have done minimal to no fill this past four days as the level in the expansion tank have remained between minimum and full even after the engine have completely cooled down. Is this to be expected as air in the system continues to be purge? I had expected that it would had escaped to the vent valve. �- So after reading an old post by Ahsai the vent valve actually releases line air into the reservoir as it has a one way valve. (Not into the environment). Once it reaches the reservoir then air is released from the pressure mediated blue cap. However there must be quite a bit of air in the system to cause coolant to also overflow from the cap. any thoughts?

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I appreciate the update. I'll be on the look out for this when I get mine going next week. And referring back to this thread. I would keep driving it and keep checking the level every time you drive it if possible. There are lots of pockets where air can get trapped. Even if you drove it spiritedly for a couple of hours. All the best,

I think i left my tab up for a week after water pump thermostat replacement. Didn't have the bubbling over quite like you but it did burp. Checked coolant before and after each drive. Added as appropriate. No issues since.

If you have 1.5 gallons left to put in the car, you should never have driven it more than around the block at very low engine loads. There is no way there is 1.5 gallons of air in your system and your car is not overheating. I would close the vent and see what happens. Drive it gingerly around your house to load it up, and remember it takes a long time to get all the coolant up to temp. Next time, get the vacuum fill tool, so necessary with these cars. I just used mine yesterday to fill my son's 2000 Audi S4 engine after we rebuilt it, sucked in two gallons into an empty block in 30 seconds.

As a follow up I got my car going yesterday. I drained a lot of coolant from the block and various hoses at the engine bay. The two big main hoses and several smaller ones. I put a new coolant tank in, and AOS. Any hose that came or went from the tank was replaced with new. I event dropped a smaller hose by oi filter. I got more than 2 gallons of coolant out. I put it all back together and filled the new coolant tank with fresh Porsche coolant. Then started the car with the pressure tab on tank in the up position. I did a traditional method and did not use vacuum. As the car came up to temperature the level in the tank dropped. I put another 3/4 of a gallon in. The level never completely dropped and I never felt a panic that there wasn't enough coolant in the system. The car was driven for a short trip and the temp held steady. After inspection in the driveway it did not need to be topped off. Overall the traditional method of filling the car was not a big deal. However, I think if one were to drop the radiators and do a bunch of work up front you would need the vacuum system to fill it. Way too much plumbing in these cars and I would not want to risk overheating. What I thought was odd was that with the coolant tank tab in the up position when I turned the cap off there was indeed pressure. The car was at temperature as it had just been driven. I figured I could unscrew the cap and take a look in. It did spray a bit, but not bad. I would have imagined that with the tab up there would not be any pressure.

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According to an old post by Ahsai the burp valve is meant to actually transfer air from the system Into the expansion tank. Then air is released around the blue cap that is pressure driven. At least that is how I understood it.