hello

i had one of engine heads replaced 2 months ago - when i get my car back i spot immediately overheating - get it back to the garage, mechanic who done the job said that thermostat must be gone. We remove it put in to the glass and flooded with boiling water - did not open. we cut it off and fitted just gasket - car runs ok, but because of winter i want to fit thermostat, so i purchased new one and same story again it doesn't open in boiling water and is rated 91 °C 195.8 °F...

*Does thermostat need pressure to work?
*If hot water is coming from bottom of the engine to thermostat - does thermostat open against water flow?
*where is located coolant temperature sensor
* how to test new thermostat

thnx for help

 

I have always heard to test them, just put them in near boiling water (or whatever the rated temp is) and they should open. Once the wax pellet inside warms up and melts, the spring is able to expand and open the valve.
What name brand t-stats are you using? It's very weird that you had two defective ones.
Hopefully someone else can chime in for your other questions.

 

Thnx for info

i put the "faulty" thermostat in to a glass and flooded it with boiling water - did not open so i get replacement and new one open within 1 min is same conditions.

One more question:

above radiator is small coolant reservoir. On the right hand side of it is small hose (top) and is connected to right top corner of radiator - as long as i remember before i give car to the garage water was always running from radiator to reservoir when engine was running now is not.
Can someone who got same engine check it for me please as im getting crazy now

Thank You

 

This is from the service manual for 2002.

"5.9L engines utilize an ambient overflow bottle for
coolant recovery / reserve. The 3.7L and 4.7L engines
utilize a pressurized degas bottle for coolant deaeration
and reserve. This degas bottle has coolant flowing
through it continuously, supplied by a vent in the
hot side radiator tank and returning to the heater
return hose.
The 3.7L/4.7L engine coolant degas system provides
a quick method for determining the coolant
level with out removing the radiator pressure cap.
With a cold engine, observe the level of coolant in the
degas bottle. The level should be in the COLD FILL
RANGE. DO NOT OVERFILL the bottle by adding
fluid above the COLD FILL RANGE. This may cause
coolant to spill onto the ground during subsequent
vehicle operation."

Doesn't mention too much more about the degas tank, but it sounds like it should be flowing. Is the small hose kinked or plugged with debris?

 

hey

hose is clean i can blow air true it... i think tmrw i connect garden hose to the return pipe and blow clean water

 

My 03 4.7 was set up that way. It should be flowing when the engine is running. Onside came from the rad, the other was hooked into the heater hose. Have you tried to flush the cooling system? Might want try to check the rad for blockages.