It seems that when I am standing still the heat gets cold. If i rev the engine a bit it seems to wam up and sometimes stays hot or gets cool again. Is this a normal porsche quirk? If not what should i do.

 

Sounds like an air pocket in the system, time to bleed it out. Plenty of posts do a search.

My heat is constant no matter what RPM.

 

Not to sound stupid but you mean bleed the radiator system?

 

yup

 

read something about this the other day somewhere Maybe the Parragon site
The thermostat on the 944 doesn't have a little bleed hole as most cars have so whenever you fill the coolant system, or you have an airlock ,you need to disconnect the hose from the block and fill it up from there then re-connect the hose and top up the header tank otherwise you get an airlock because the air cannot get past the thermostat until its hot enough to open. phew
jeeper sounds like your thermostat might be packing up or getting stuck

 

Thanks peanut. How much and how hard to change?

 

oh real easy to do (not that I have changed one on a 944 yet)
Cost I guess about about $20-35.00 aftermarket part from an auto accessory store

It sits inside the hose which enters the water pump housing Just undo one jubilee clamp pull off hose, remove snap retaining ring, pull out and replace thermostat.Watch out for a detachable rubber ring gasket

Dont forget to top up coolant to top of hose before inserting new thermostat and retaining ring. on the thermostat and make sure you put the thermostat round the right way.

Check out the pictures on page 93 of Haynes manual

You can check the thermostat works by heating it in a pan of water on the stove with a cooking thermometer. It should open fully at the temperature stamped on the thermostat and close fully about 10 degrees below that temperature. Check you have correct thermostat temperature rating for the part of the world you operate the car in. Good luck