Advice: do not have your coolant flushed before replacing your expansion tank
 

last year I decided to be a good Porsche boy and flush my coolant even though they say to never do this. That just didn't make sense to me after 10 years. The coolant was cheap($30) but the labor was a bit more than I was expeciting since I've never done such a job or have the tools for it. All in it was about $300.

Well less than 12 months later the expansion tank crumbled under the pressure of my merciless driving and a tiny hairline crack dumped all the coolant over the course of a day. So you guessed it...time to do it all over again plus a new tank (about $350 on Ebay).

Save yourself $300 by doing it once.

With respect, two events are probably unrelated. If your coolant has never been flushed, I'd say it's a good idea to do it ASAP regardless of whether you have a new or old expansion tank. They don't all split. My '97 still has its original tank. I replaced my coolant when I fitted new rads and pump a while back.

you know you just jinxed yourself right? :D

I disagree on both counts...
 

... first, I believe both events are related.
I have always said that the coolant reservoirs tend to crack when there is air in the system.
By having flushed the coolant it is very likely that some air was left in, causing the crack some time later.
Most of the coolant reservoirs (not to say all) that I've replaced had has the coolant replaced within the last year or so.
My coolant reservoir is still OEM. It is 13.5 years old and has 208,000+ miles.

Second, don't flush if you don't have to.
Porsche says it's a lifetime coolant and it is.
When I installed my 3rd radiator at 125,000 I saved the coolant and reused it.
It was clear and looked new.
At 203,000 miles the engine broke a piston rod and the coolant again was crystal clear.

The cooling system is a closed system. Nothing should enter to contaminate it unless you either put it in yourself or oil penetrates because of a bad oil radiator cracked cylinder or bad head gasket.

Happy Boxstering,
Pedro

Got to agree with Pedro on this one; I have often suspected that if these systems get air bound, they develop a pressure surge not unlike the water "hammer" you get in home heating systems or water lines when they have air in them, which the tanks apparently do not like. Systems that have been refilled under vacuum do not seem to have anywhere near the number of tank failures that systems that have been "burped" after refilling under atmospheric pressure, and systems that have experienced problems with air trapped in them seem even higher.

Pedro is spot on. After the coolant was flushed last year I noticed there was an air bubble in there becase I was getting a false half empty measure on the indicator. Wasn't running hot and neither did the dashboard light start blinking. Not sure where the airbubble went but the indicator rose back to normal level. Well on second thought I guess I do know where the air bubble went, it made its own exit.

So yeah, don't flush and if you do get ready to spend $300 on a new unit. Luckily I was at home when I noticed all the coolant was gone.

You should've posted this thread a year ago..

I changed my coolant last summer and followed instructions on Pedros Garage to burp the system..

My coolant tank is still OK.. I think it's still alive because o-rings on my bleeder valve were toasted and condenstation was getting out.
But now I wonder if I should open the bleeder valve and drive it for the rest of the summer to avoid coolant tank change...

Sasha

post hoc ergo propter hoc

Heh, yeah, you may have a point.

Still, I followed the multi-step burping process with forensic care and a thousand miles or so later, appears to be OK. I managed to fit all but a couple of litres at most of my 20 litres of freshly mixed coolant, so hopefully, there's little or no air stuck in the system.

I think my coolant had a mix of coolant types in it due to a slow leak from one rad. I was always going to loose a lot of coolant changing the rads and pump, so for me I maintain it made sense to totally flush the system.

I also think that over time any coolant is likely to get a little contaminated and see its electrical insulating properties degrade leading to damaging electrolysis.