Coolant woes - 986 Forum - The Community for Porsche Boxster & Cayman Owners

antny · 04-10-2015, 01:44 PM

So this past week I did a water pump and a 160 thermostat swap. After the swap I was able to pull vacuum with a uview and filled the system back using Porsche coolant. Car seemed fine and took it around the block to see if there was any air pockets. About a block away from the house the temp started to rise and I was able to make it home within a minute later. I look in my driveway and there is a puddle of coolant and trail of coolant down my street. The leaking is coming from the right rear tire area. That I would assume is my yellowish expansion tank took a dump on me. I was able to fill the system back up at 22 PSI of vacuum. I started the car back up t see if it was going to get hotter than 180. It did not climb but the temperature light started to flash. I turned the car off immediately and checked to see if there were anymore leaks from the expansion tank area which there were not.

I already ordered a new expansion tank but with it not leaking again and the temp light flashing what else could it be???

Thanks all.

Steve Tinker · 04-10-2015, 02:04 PM

Ant.... assuming that you installed the water pump & T'stat correctly, there could still be an air pocket in the system.
As a quick check that there is no trapped air , flip up the expansion tank release valve - its a chrome half ring mounted on top of the tank. Move the ring into the vertical position and leave it there for at least 2 -3 heat cycles. After each run, let the car cool completely and then check the volume of coolant in the tank - if it drops then there is a good chance you had an air pocket.
After the 2 - 3 heat cycles the level should stabilise. You can then return the valve to its normal position.
Note: A heat cycle is not driving round the block, its driving for at least 5 miles or so to get the T'stat fully open.

antny · 04-10-2015, 03:15 PM

Thanks Steve. I did drive it about 6 miles when it decided to puke coolant down my street. Sorry for the lack of description. When I refilled the system I started it let it get to temp and then the light started blinking wth the temp gauge only being right above 180 F with the bleeder flipped up. If it had air in the system would it pour that much coolant out the over flow? When I say a lot it was over two gallons of coolant that went back in.

antny · 04-10-2015, 06:37 PM

You were right. There was a lot of air still in there. She is staying rock steady now. Thanks for the advice. I as just scared from when it lost so much coolant earlier and the light flashing.

Steve Tinker · 04-10-2015, 06:47 PM

Damn - you posted as I was (slowly) typing, but this is what I said - hope it helps. Pleased you have got it fixed....

That doesn't sound right.....if you already had the bleeder valve in the open position.

When I replaced my coolant (a couple of times now) I did it manually. If you have the Bentley manual there is a better description but in a nutshell here's what I do:

1) Have the rear of the car up so any air in the rads can migrate back up.
2) Heater turned to max (ignition must be on to operate) & bleeder valve open.
3) Start pouring in coolant until tank is @ max.
4) Start engine and leave running until T/stat starts to open and level drops.
5) Top up tank & give engine with a few blips of the throttle to 4-5000 rpm and wait for front rad fans to kick in and out a couple of times.
6) Let engine cool for an hour & check coolant level - add as required.

I then lower the rear of car, screw on filler cap, keeping the purge valve open and take for a drive watching the coolant temp gauge. I usually leave the purge valve open for 2-3 days as you still may have to top up the coolant level.

antny · 04-10-2015, 08:57 PM

Thanks again Steve. I was hoping the uview was going to alleviate all air in the system problems. It did not and gave me a oh crap moment when I the car purged a ton of coolant from I am guessing it boiling over. I was sure I had the expansion go on me but when I refilled it with coolant it stayed bone dry. Then after having the car run after refilling the red light was blinking at me. I drove around tonight with it blinking just watching the gauge and it went away. I just had bad luck with a BMW motor popping a head gasket from overheating. This is not a motor I want to shell out money to replace so it gave me the not so good feelings. Car ran great all night when I took it out for about a 50 mile drive. Thanks again!