Porsche Repair: Cayenne S overheating, coolant loss, coolant system

Question
QUESTION: Hi Brad,

I have a cayenne S that has a over heating problem, I replaced the coolant pipes that run under the inlet manifold( the old ones were plastic and the replacement ones are aluminium) also sorted the thermostat and replaced the water pump.

I let the vehicle run for 2 hours then went on road test, when I came back i let the engine idle for about 20 mins and noticed the Water temp gauge started rising above te 1/2 mark. just when it almost got to the maximum level the coolant reservoir exploded in half!!! before this happened I checked the water pipes coming out of the radiator, going into the engine and both of them were equal hot temp, also when I touched the engine it didnt seem hot, although the gauge showed the temp was over the 3/4 mark. what could be causing the over heating?? will a replacement reservoir and coolant cap solve the problem?? (I suspect the cap wasnt releasing any pressure)

I also put the cabin temp to maximum hot but noticed that the blower was still blowing cold air, could this have anything to do with it??

also how do you bleed the cooling system??

any help would be greatly appriciated

thanx in advance

ANSWER: When did the overheating problem start? Before or after the work you did?
What do you mean sorted the thermostat out?
Why did you replace the water pump?

It sounds like you have air in you cooling system.
The proper way to fill the coolant per factory spec is when the system is empty, you connect the coolant vacuum pump to bring the coolant system to a vacuum, then when releasing the vacuum the special vacuum apparatus will replace the vacuum with coolant, eliminating any air pockets.

If you don't have this tool, you can risk damaging the engine due to overheating. The same tool is also used on Boxsters, and I believe the early water cooled vw vanagons.




---------- FOLLOW-UP ----------

QUESTION: the whole reason I changed all the parts was because of over heating, I noticed coolant loss around the water pump area,(rust colored  residue) so decided to change all the pipes while i had it opened.. its a 2003 model by the way.

As for the thermostat I removed it as it didnt open while testing it( I know thats a bad idea but I dont have access to a replacement yet and its an emergency measure)

Could this have affected the water system in some way?? and Why isnt the heater in the cabin blowing hot air? would this cause the reservoir to explode?? it split neatly in the middle along the seam,

also there has got to be another way to bleed the system, there are no porsche dealers in Kenya so I cant take it to them.  

Answer
Some thermostats assembly's do a couple of jobs, one being regulating water flow, but when closed they allow the water to bypass. If you have the t-stat out, it may be bypassing all of the time. This SUV has a complex cooling system.

The heater isn't working because there is no water flowing to the water pump like there is a big air bubble there, also the temp gauge my not read correctly too due to the lack of water. Then the engine gets super hot boiling what water is in the engine causing massive pressure and Pop, there goes the weakest part, the plastic expansion tank.

When the engine is cold, try disconnecting the upper radiator connection. Get a pressure water hose (garden hose) (hopefully you have pressurized water where you are) and try to force water throughout the engine eliminating air pockets. Once it seems there is no air, Seal the  coolant hoses, start the engine, turn on the heater, rev the engine to 25oo rpm, closely monitoring the water level and add if needed. Do this until the heater is blowing hot, and the water level is correct.
I still don't know if this will work without the t-stat.

Goodluck

BRad

www.btmmotorwerks.com