When I drive at higher speeds, the temp. spikes up to 110 and coolant spews out of vent hole in my resevoir. When I turn on the heat and crank the fan, temp goes down. I'm thinking coolant flow issue??? I've changed the water pump, thermostate, head gasket, fan works, rad looks fine.....hoses look fine....Help!!!!
Check your hoses, especially on the suction side. A weak hose will collapse at high speed causing exacty what you describe.
Peter Wieck Wyncote, PA
Can you possibly explain the location of a hose on the suction side????
A radiator has two hoses. One gets water sucked from the radiator to the pump. The other puts water in that has passed thru the engine block.
Since the top of the radiator could have air, they suck from the bottom.
Also try a new radiator cap. Testing that new thermostat might be a good idea too. Does it overheat at lower speeds? Any debris blocking the cooling fins of the A/C Condensor or Radiator?
It doesn't do it at lower speeds, but if it is really warm out and I turn on the a/c (makes engine work harder) it will start to run hot....my next to cheap tests are the thermo switch or the resevoir cap.
Snipped thread so I lost track of what you did. Some water pumps are reputed to have plastic impellers. Is there a chance that your impeller is slipping?
My 2003 Jetta has two electric radiator fans. Is your one or both fans working? My 1984 Rabbit had rubber flaps close the the radiator fan. The theory was that at higher speeds the air would blow through the radiator, out those flapper ports and also past the fan. At slow speeds the fan would suck the rubber flaps closed and air would be drawn through the radiator and condensor.
On my gas powered 1987 Toytota it runs a little bit cooler when I replaced the air flow sensor. I need to replace the oxgen sensor as it is probably over a decade old. A lean running engine will/can run hotter than one running the proper mixture.
I've came across a problem similar yours, which was the result of a missing thermostat.
Verify (with the car running) that the coolant bleed line from the head to the reservoir tank is hot, and actually has coolant flow. That particular outlet on the head-side on your model vw is notorious for becoming corroded and keeping air pockets trapped in the engine.
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