PHIL928

This is what happens when the weakest point in the cooling system is not the radiator cap.

SeanR

WTF?

Ducman82

what could that cap have been from?

PHIL928

I believe the 944 turbo runs a 150KPa cap.

This was done by the most well known and "prestigious" independent Porsche garage out here...

dr bob

For those playing at home, the factory cap is rated at 100 kPa, same as ~~ one atmosphere or ~~15 PSI. The 150 kPa cap is 50% higher or about 22 PSI.

Rob Edwards

22 psi will do _that_ to a radiator core? Pin hole leak that fails explosively?

The only radiator I've ever seen like that was after a 2 foot prybar was used to separate it from the crank pulley after an off-road excursion.

FredR

Phil,

What temp was indicated on the dash when this happened? I thought you chaps had cooling well sorted?

Let's hope the damage is limited to the radiator.

Best wishes

Fred

docmirror

Not that I know of. I think they are all 16PSI. My 968 is 16.

IcemanG17

WOW........my guess is there was significant clogging inside that radiator that caused the explosion....if I am seeing the pic correctly its the bottom that blew out...makes sense that all the minerals-gunk would end up there....

PHIL928

Fred I believe it did actually hit 100+ would have probably had to hit higher than that to get it to spew out of a 150KPa cap.

What other problems do you reckon such pressure may have caused?

We had not touched the cooling on this one until now. I think she's getting a brand new full aluminium high performance radiator. New thermostat+seals and radiator hoses on their way from Roger.

BTW this is from a 95 GTS, to give you an idea

PHIL928

I think you are absolutely right. However the top side blew out more than the bottom, probably because it has less force holding it flat.

I just took the thermostat out to see if there is any corrosion or blockage and this is what the thermostat elbow looks like. Coolant had not been changed in 5+ years, driven regularly but not for a far distance. So the inside of the radiator must be spectacular.
But this makes me wonder, what about all the coolant journals and jackets. If they are this packed up, then surely the car cannot be cooling effectively. Which explains alot.
Here's a pic:

SMTCapeCod

What's the gold material- any chance that's some kind of leak fixer? Any cylinder issues ie head gasket?

I"m tempted to look up an old thread on here that rationalized how smaht it was of Porsche to design a frail plastic heater valve that would blow off under excess pressure, in advance of other parts coming to harm.

PHIL928

I think that gold is just from a tiny leak over time with decade old coolant slowly leaking out.
No other symptoms so far! I hope it stays that way!

FredR

Phil,

If the radiator blew apart like this then one has to be concerned about the heater matrix [if that is connected]]. The heater valve stops circulatation but it does not stop pressurisation of the system. I presume you had the a/c on- not the heater! I doubt the increase in pressure would be enough to cause the head gasket/water jacket joints to blow or weaken but for sure it will not do them any good.

On a more positive note the heater matrix when static probably sits at a slightly lower pressure than the water jacket. Remember, the pump adds head to circulate the fluid but the system static pressure is largely controlled by the operating temperature, the header tank cap retains system pressure thus elevating the boiling point to keep the coolant in the liquid state. However, even in the static condition, the heater matrix will see the same back pressure as the radiator it is in equilibrium with.

When it went pop I bet it was quite an impressive site- big steam release coming out the sides/front of the bonnet? Must have looked like Thomas the Tank Engine for a minute of so!

As the radiator let go I presume the pressure cap held pressure?

One of the alleged reasons for using the short hose from the block to the heater valve is that this supposedly lets go before anything else. Whether correct or not I do not know.

It may also be be wise to replace all the water hoses if they have been over pressured- especially if they are oldish.

Regards

Fred

FredR

Phil,

Another point that many do not understand is that whereas the coolant will last more or less forever, the anti corrosion package in the coolant does not- in simple terms it gets used up irrespective or whether the motor is used or not. This is another good reason to use Redline water wetter in that it also contains an anti corrosion package. I have long theorised that motors that show corrosion at the top of the cylinder wall on the water side do so because the coolant has sat stagnant for too long in the spent condition and thus corrosion sets in. Engines that are run regularly and have the coolant changed regularly and or anti corrosion chemicals added every couple of years probably show no corrosion.

I also suspect that engines that run hotter may also consume the anti corrosion chemical package that bit quicker. Thus may the radiator failed due to a combination of higher pressure and general weight loss corrosion to some extent.

Regards

Fred