radian1983

Hello, I have Porsche 928 S, year 1983, and I have problem with engine overheating, Temperature goes after 15-20 km to the red. The electric fan starts at the red, the sensor is 85/80 °C. Engine fan is going. I changed the thermostat, want also put the seal behind the termostat, but the new seal ring is not going inside (too big), probably it is older model which does not have it. The cooler was cleaned by cleaning liquit. Cap of water reservoir is changed. I checked the water pump function and after pulling out the upper water tube and start heated engine (termostat opened) then the water is coming from the tube, so I suppose it is working. Nevethless the cooler is heated at the top and on the sides (etc.90°C), but in front of the coole is about 30-40°C. The head gasket I think is OK, no pressure to the tubes or reservoir. no oil in water. I think it can problem with cooler or with the termostat (no back sealing). Can anybody advise me?

Darklands

Is the visco blower broken?

radian1983

The visco blower is function.

Darklands

300, 310 or 240 hp?

Mrmerlin

based on this report replace the fan clutch.
if that doesnt fix it then replace the water pump,
dont use a rebuilt pump.

soontobered84

Does this mean that you did not put the seal in place behind the thermostat?

If you did not put that seal in place, that is why your engine is overheating

Speedtoys

http://www.autoatlanta.com/porsche-p...section=105-05

#33

Tom. M

Sometimes the sealing ring behind the thermostat looks like it's part of the housing and a new seal won't fit inside the old one obviously. Pry the edge of the raised area in behind the thermostat and you'd probably be surprised that there is a seal there.

Mrmerlin

FWIW the rear T stat seal may not be a part of this engine water bridge
IIRC This seal started in late 83 But all that means is carful scrutiny must be made to determine if in fact this WB doesn’t have this seal

radian1983

The engine is 310 HP. The hole behind the termostat is 36 mm and the rubber ring is 41 mm wide. There is not visible, that there was originaly. Why Porsche started to give the rubber ring at the end of 1983, they found that without the rubber ring it is not perfect. Have cars, which does not have it originaly problems with overheating? What about to glue some rubber directly to the termostat? Is there any possibility to avoid the termostat (make some bleeding and let the big water cyrcle opened)? How can I check the good function of waterpump without demontage? I checked it by taking out water tube and start engine, the water then leaked out. The termometer shows good temperature. Leakage is not visible. Is it possible to be some water buble in the system?

Mrmerlin

From the picture you have an early WB so no rear seal will fit

follow my other suggestion

try another T stat

fan clutch replacement unless yours is new

if no change then water pump replacement

if no change then head gasket replacement.

Note in order of cost

Petza914

Before installing the new thermostat, put it into water that you're heating up and see at what water temp it starts opening and at what temp it's fully open. Do the same rith the one that was installed to see if it's actually working.

Get yourself and AirLift vacuum fill tool. This lets you not only pull a vacuum on the system once reassembled that will show you if you have any leaks before filling the system with coolant, but will also let you fill the system without any air pockets.


If the system has integrity, the vacuum will remain indefinitely. If the needle starts dropping, you'll have a leak once you have coolant in the system. This allows you to find any leaks without having to drain the system and clean up leaked coolant.

Darklands

310 hp is modelyear 84. O ring behind thermostat not for this car tells me rose passion.

mkhargrove

you're absolutely 100 percent certain that you don't have air in the system? the only way i've been able to make sure i get the air out is to fill it up with coolant, leave the cap off and let it run until very warm. bouncing the car seems to bring a few bubbles to the top. shut it off, still with the cap off and let it cool, and the air seems to mysteriously bubble out. i've done it on a flat driveway....i don't know if tilting the car in any particular direction would help. but, air in the system allows for expansion/boiling of the coolant, which makes the water pump cavitate. the car will warm up until the coolant gets hot then when it can boil, the temp moves up quickly.

Mrmerlin

FWIW the 928 cooling system is a self bleeding system,
it bleeds air from the top of the radiator and the top of the WB,
both of these lines return to the top of the cooling bottle.
So no tools are needed to fill it and have all the air come out.

To fill a 928 cooling system ,
Open the heater control to hot,
fill from the cooling bottle,
once the bottle maintains a half seam fill , this will be close to 4 gallons of liquid.
then start the engine and let it warm up till cooling fans come on.
If no cooling fans then monitor the gauge till the engine reaches normal temp,
then fit the cap. Make sure you have a good cap replace it if over 10 YO

Take the car for a 5 mile drive with the heater on.
Park the car and let it cool off ,
top off the system once the engine is cool.