martydonna

I am having great difficulty in sorting out my Overheating on my 1993 1.8 Passat.
I have replaced the thermostat and the problem is still there.
When the engine is run for about 5 minutes it boils over without even operating the fan.
Also the air blows cold even when selected hot with one hose getting hot and the other staying cold ( the inlet and outlet hoses that pass through the bulkhead)
Could it be the head gasket or does anyone know what could be causing the problem?

Many thanks,

Martin

boschmann

Does the hose coming from the thermostat to the radiator ever get hot? Did you recently have the coling system drained (before the overheating)?

martydonna

Yes a hose burst, was replaced, got it running now but gets to temp rather quickly, water stays in the expansion tank unless the liod is of then it bubbles out everywhere, heater gets hot, then goes warm, sometimes cold.

My mechanic suggests the head gasket is blown leaking air into cooling system, unfortunatley the poor beast of a car is going into early reitrement if thats the case or maybe a hibernation until such times as I am a millionaire and can send her up to the garage to be fixed!

boschmann

The best case would be that you have an air bubble stuck in the engine. You can try removing the upper hose & fill the engine directly from there. With the cap on does the lower hose & radiator get hot? Does the cooling fan come on?

martydonna

with the cap on everything works except it gets hot really fast, with the cap off it spills out the water, lower hose gets hot and yes the fan cuts in at about 90, but the engine wont even cool down when cruising on a cold day at 80mph!

boschmann

If you feel around different spots on the radiator is it uniformly hot or are there any cold spots? Did you see if it builds pressure in the system after it warms up? Do you have tools to do a compression test?

bunman67

Boschman, I too am having similiar problem ,I tried filling system from the top of block and the top radiator hose but no luck ....my top rad. hose is hot but the bottom hose is cold while the rest of the system is hot and under pressure ohh yeah and the new resevoir i installed is spewwing the coolant out....(the other i broke the small return hose nipple off)any advice would be helpful....thanks, JAMES

martydonna

Unfortunatley when I tried to start the car this morning there was evidence that she was firing only on 3 cylinders, the other one was full of water, The coolant system had been filling with pressure from the cylinder when the engine was fired up and this was also evident when the cap was taken off the resevoir as I could smell petrol etc in the water/coolant!
Best I get saving up for a costly job as I will not scrap the car as its otherwise mechanically and structuraly sound!

boschmann

Martydonna, you are indeed in for some work, classic blown head gasket (at least).

Bunmann, the coolant evidentally isn't circulating. Easiest thing to do is replace the thermostat. How did the coolant look, any chance of a clogged radiator? Last possibility is the water pump impeller, but that is not common.

bunman67

SORRY TO HEAR THAT MARTY!!.....BOSCHMAN,I will put a new thermostat in thursday and try again....will let ya know what it looks like from there...thanks, JAMES

bunman67

Ok Boschman...not so good!! Installed new thermostat, i now have a radiator that is hot uniformly and my bottom hose is now hot, but i kept belching it and sqeezing it until it filled and got hot coolant in it. noticed the new thermostat opened as needed.but i am still having an overheating problem!! I have been using the "mix with any color Prestone" to top off and refill and i am wondering if i need to go to my dealer and get some G-11...thinking that after i lost a minimum of 50% mix that it just wont cool correctly....just guessing now ,,,and oh yeah it appears to be circulating correctly(water pump working) and i checked the spark plugs and there is no evidence there is is coolant entering the combuistion chambers.....james

boschmann

If you're sure there were no air bubbles & it now gets hot at the lower hose then I'd start worrying about the radiator. The coolant mix won't make any difference at this point. If the fan runs & coolant circulates (you should see it spraying out the small hose into the reservoir) then I'd say the radiator is a bit old & not cooling efficiently, 15 years is a good run.

bunman67

The fans are only running after shut down i have noticed.Where is the thermo switch for them? Am not sure there are no air bubbles but i am gonna try to belch the system some more today.

boschmann

There is an afterrun cooling fan thermoswitch in the cylinder head cooling flange, ground the wire coming from it & the fan should run. The regular cooling fan switch is in the radiator, jumping red to red/black with the key on should run the fan on high. Jumping red to red/white should run the fan on low. See which works.