Coolant Questions

chrisjcoe · Dec 11, 2012

I heard a slight gurgling liquid sound the other day, from behind the dash. I suspect I have a bit of air in my coolant, and I know that my coolant low and due a top-up anyway. So, my questions:-

Would you just top up the coolant, or would you completely drain the system and fill it up from scratch? If you think I should renew it, then I'll have a load more questions. If it's just a nice-to-do job, then I might top up for now and renew the coolant in the spring.

I understand that phosphate free coolant is required, is Prestone the right stuff to get?

I also understand that tap water is not ideal to use due to its content of minerals. I have a dehumidifier running most of the time at home which produces a few litres of water a day, could this be used as 'distilled water'?

bighead · Dec 11, 2012

if yr coolant is recent...I would just bleed the air out , run engine with heater on max position, open bleed valve (somewhere near the inlet maniflow depending on which 944 model to have ) and let the coolant run out till you cannot see any bubbles in the coolant comming out from the bleed valve/bolt, then tighten the bleed valve and top up the coolant tank.

chrisjcoe · Dec 12, 2012

Thanks. No idea how recent it is as I've only owned the car since about June. It was stored for a couple of years previously but was put back on the road before I bought it, although it needs a fair amount of TLC. So I would suspect it's not too recent, but also it could have been done when preparing for the MOT. I am not in contact with the previous seller or the guy who took it out of storage to ask unfortunately.

I think I'll take your advice as soon as I can spend more than 5 minutes outside without losing all feeling in my fingers. Then, in spring, will renew it. I can't see me driving it much in the meantime, my main car told me that it was a lovely -4 this morning, not ideal 944 weather.

pauljmcnulty · Dec 12, 2012

Try to park it facing uphill, helps a lot with bleeding.

chrisjcoe · Dec 12, 2012

Thanks Paul, i was going to put it on axle stands at the front. It won't be steep, but better than nothing!

bighead · Dec 12, 2012

ORIGINAL: chrisjcoe

Thanks. No idea how recent it is as I've only owned the car since about June. It was stored for a couple of years previously but was put back on the road before I bought it, although it needs a fair amount of TLC. So I would suspect it's not too recent, but also it could have been done when preparing for the MOT. I am not in contact with the previous seller or the guy who took it out of storage to ask unfortunately.

I think I'll take your advice as soon as I can spend more than 5 minutes outside without losing all feeling in my fingers. Then, in spring, will renew it. I can't see me driving it much in the meantime, my main car told me that it was a lovely -4 this morning, not ideal 944 weather.

well if thats the case ...I would change it now as it been in there a few years , really the same procedure, drain coolant , flush engine and raidator, fill up with fresh coolant and then bleed it (half-1 hour max ).

I was quoted by Hartech in bolton around £90 to do the change, so I though I can do it myself for the price of coolant

chrisjcoe · Dec 12, 2012

About an hour would be manageable in this weather! I've read the clarks guide. It's pretty comprehensive and recommends getting a new drain plug and seal. I'd have to follow the gravity method of filling/venting.

Also there is a brief guide here which describes another approach:-

This is the procedure I used. Run the motor for a few minutes and wait for the cooling fans to turn on, the second they turn off, turn OFF the car, get under the vehicle and loosen/open the lower radiator rubber pipe coming from the lower passenger side. The thermostat is open at this time, so ALL the coolant will flush out. After, tighten the hose, and u can poor water in the system and run the engine to flush out any dirty stuff (optional really), and do the same procedure again. Just be careful when running it with the water in, you just dont want to do it for too long, just long enough for the fan to turn ON then OFF, and then go and drain it at the same spot.

After you've done that, go ahead and fill the system back up with Coolant (the Porsche coolant I got, I mixed with 50/50 distilled water)

A lot different to Clarks, and also seems a lot easier, but in my experience easier is rarely better. Should I closely follow the Clarks instructions? Also, would this coolant be find with dehumidifier produced water?

robdimond · Dec 12, 2012

I've never had problems bleeding the cooling system on my S2... I think the difficulty bleeding only relates to the 2.5.

You certainly want to change your coolant as it's not worth the risk that the coolant of unknown age/composition will freeze and crack the head/block. An antifreeze tester will give you peace of mind if you don't want to do it right now.

I recommend getting a new drain plug, mine cracked on removal. Also worth making a little duct with 1/2 a coke bottle or similar otherwise the coolant drains onto the front bumper trim and will make a mess.

IMHO the best way to bleed any car is to have positive pressure on the header tank and then crack the bleeder valve. If you don't have a pressure tester then just seal a hose/funnel into the header tank so that you have a head of coolant well above the bleeder.