Engine temperature go up only in high speed in cold weather

[Andrepatry]

Villager 1998 - 105,000 km

I have a very strange problem with the engine temperature. The temperature of the engine is awfully slow to go up at low speed (city driving). However, once I hit the highway, the temperature goes up to normal after a few kilometers of driving. The heater however works well and I have normal hot air coming out once the normal temperature has been reached.

During extreme cold condition, it takes a lot more kilometers of driving before the temperature reach the normal level.

I have changed the thermostat. (I have checked the old thermostat in hot water with a thermometer and the test came out ok). But I put in a new one in the engine just in case.

I have also flushed the system with special fluid that I purchased for that purpose.

But still, I have this problem with the engine temperature. What I don't understand is why would the temperature of the engine go up only when the engine RPM increases??? As soon as I go back to idle, the temperature goes down again.

I have called a few radiator shops in Ottawa and no one was able to give me a reply to this problem. I would appreciate very much if anyone could. Thanks

[eltigre]

You have to look at a few things: If you replaced the thermostat and are SURE that you installed it correctly(with the jiggle valve up and long end toward the hose) ...then look at(not necessarily in this order):


1) Radiator fan operating correctly with no fins broken
2) Check the water pump and make sure that the belt tension is correct and that the pump is not leaking
3) or you may have a bad coolant temp sensor

good luck

[Andrepatry]

Originally Posted by eltigre

You have to look at a few things: If you replaced the thermostat and are SURE that you installed it correctly(with the jiggle valve up and long end toward the hose) ...then look at(not necessarily in this order):


1) Radiator fan operating correctly with no fins broken
2) Check the water pump and make sure that the belt tension is correct and that the pump is not leaking
3) or you may have a bad coolant temp sensor

good luck

Thanks for the suggestions. I will check suggestions 1 and 2. I doubt that the sensor is defective because when the temperature gage is low then the heat from the heater is not very hot, meaning that the gage is performing correctly.

I will check the thermostat again afterwards and let you know when I find the problem! Take care!

[eltigre]

Good Luck.......BTW, those are all signs of a thermostat stuck open.....Are you using Failsafe thermostats?

[Andrepatry]

Originally Posted by eltigre

Good Luck.......BTW, those are all signs of a thermostat stuck open.....Are you using Failsafe thermostats?

I don't think that I am using a Failsafe thermostat but I am not sure. I remember that I was hesitating at the time of buying because I had a bad experience with a failsafe thermostat who was getting stucked opened for no reason. But nevertheless, I think that I am going take it out and put in quality one from the dealer. The one that I put in was a cheap version.

I have to change the thermostat on a Villager. It is not well located and very hard to get at.

Thanks again!

[eltigre]

Originally Posted by Andrepatry

Thanks for the suggestions. I will check suggestions 1 and 2. I doubt that the sensor is defective because when the temperature gage is low then the heat from the heater is not very hot, meaning that the gage is performing correctly.

I will check the thermostat again afterwards and let you know when I find the problem! Take care!

BTW are you sure you checked the right coolant sensor...some models have TWO...one that's for the temp indication on the dash and the other is for the computer ECU

[Andrepatry]

Originally Posted by eltigre

BTW are you sure you checked the right coolant sensor...some models have TWO...one that's for the temp indication on the dash and the other is for the computer ECU

Assuming that the sensors are used to report/indicate the temperature only I do not see how they could interfere with the engine heating process. The problem that I am having is with the engine taking a long time to heat up and not keeping its temperature at idle speed. Can the sensors in any way impact the heating up process of the engine? If so, would you mind explaining me how that can happen.

I strongly suspect that the problem is with the thermostat as you mention previously. So I will start by that.

PS - May I ask you something else: During the refilling process of the antifreeze, there is a procedure to follow in order to bleed air from the system and avoid overheating the engine. I follow that procedure as described in the Haynes Repair Manual. In the procedure I need to loosen/remove the air relief plugs, one on the radiator and the other one near the back of the upper intake manifold (plenum) while refilling. That is no problem. However, I also have to find the the Air Relief Cap for the heater pipe, located behind the throttle body and attach a length of hose to its fitting and run the hose to the coolant reservoir. The problem is that I cannot find that Air Relief Cap. Can you help me with that? Thanks

[eltigre]

Originally Posted by Andrepatry

Assuming that the sensors are used to report/indicate the temperature only I do not see how they could interfere with the engine heating process. The problem that I am having is with the engine taking a long time to heat up and not keeping its temperature at idle speed. Can the sensors in any way impact the heating up process of the engine? If so, would you mind explaining me how that can happen.

I strongly suspect that the problem is with the thermostat as you mention previously. So I will start by that.

PS - May I ask you something else: During the refilling process of the antifreeze, there is a procedure to follow in order to bleed air from the system and avoid overheating the engine. I follow that procedure as described in the Haynes Repair Manual. In the procedure I need to loosen/remove the air relief plugs, one on the radiator and the other one near the back of the upper intake manifold (plenum) while refilling. That is no problem. However, I also have to find the the Air Relief Cap for the heater pipe, located behind the throttle body and attach a length of hose to its fitting and run the hose to the coolant reservoir. The problem is that I cannot find that Air Relief Cap. Can you help me with that? Thanks

You're right the sensor has nothing to do with the heating up process...it was just a "FYI".......as for the heater air relief ...it is located behind the TB between the TB and the EGR valve...it should be a small CAP...it's not connected to anything it is JUST a cap....good luck

[Andrepatry]

Originally Posted by eltigre

You're right the sensor has nothing to do with the heating up process...it was just a "FYI".......as for the heater air relief ...it is located behind the TB between the TB and the EGR valve...it should be a small CAP...it's not connected to anything it is JUST a cap....good luck

Thanks for the info. I will check it out tomorrow. I appreciate your help.

[NocturN]

When filling the cooling system, bleeding the air out of the system by opening these air valves is very important. It allows air to escape and the system fills with water not air. i just wish i knew that before i 86'd the head gasket from running too hot.