98 Voyager Engine is not hot

[Amechanic]

Hi all, I have a strange situation where the engine of my 98 Voyager is not hot no matter how long I drive. On freeway, it even gets colder. My hand can touch the engine. The temperatuer gauge is low. Hot air is not hot. I also get lower mpg - about 15-20%. Appreciate any help.

[aldovera]

It could be a thermostat stuck open. Is your coolant at proper level?

[Amechanic]

Originally Posted by aldovera

It could be a thermostat stuck open. Is your coolant at proper level?

The coolant level is normal. If thermostat stuck open, why engine is cold? Thanks

[aldovera]

Because the thermostat is supposed to create a flow restriction to raise the coolant temperature if it is stuck open it is not doing its job.

[Amechanic]

Originally Posted by aldovera

Because the thermostat is supposed to create a flow restriction to raise the coolant temperature if it is stuck open it is not doing its job.

It works after replacing the thermostat. Now I noticed another situation where it seems to be no enough pressure in the radiator because the upper hose is flat (easily squeezed) and I can take off the radiator cap without the need to cool down the engine. Any solutions? Thanks.

[waltham41]

Try getting another cap or look for a leak somewhere. Something is keeping it from building up pressure.

[aldovera]

When you changed the thermostat and replenish the coolant did you let the air out of the system?

[Amechanic]

Originally Posted by aldovera

When you changed the thermostat and replenish the coolant did you let the air out of the system?

How to get rid of the air? I'll replace the radiator cap. Thanks

[aldovera]

Top up coolant level at radiator, start the engine but leave cap off. Let the engine run until normal operating temperature is reached. At this point the thermostat should open and you will see the coolant go down and some bubbles come out. Continue topping up coolant until no longer goes down or it starts overflowing. Turn engine off and replace cap. That should let the air out.

[HeadlessHorseman]

Originally Posted by Amechanic

How to get rid of the air? I'll replace the radiator cap. Thanks

This isn't the only way or the quickest way, but it may be the SAFEST way, I think... Park your vehicle on a FLAT surface (VERY important!). With the engine COLD, remove the radiator cap. If you have air in the system, your coolant level will be low in the radiator. Your expansion tank will probably be empty.

Add a 50/50 mixture of coolant and water directly into the radiator until it fills all the way up to the top. Put the radiator cap back on to the radiator. Now check the coolant level of the coolant expansion tank. If it's low or empty, add a 50/50 mixture of coolant and water to bring it to the "MIN" level. NEVER add water to the expansion tank! Always mix your coolant and water (50/50) BEFORE adding it to the coolant expansion tank!

Start your vehicle. Take it for a 5-10 minute drive or let it idle until the thermostat opens and is circulating coolant through the radiator. Park it and turn the engine OFF. After the system has cooled down, remove the radiator cap again (NOT WHEN IT's HOT!). Check the coolant level again. If low again, add a 50/50 mixture of coolant again.

Repeat this process until all air is out of the system (when you can remove the radiator cap and the coolant remains at the top of the radiator).

AFTER you are done and the engine is COLD, check the coolant level of the expansion tank AGAIN and make sure that the coolant level is at "MIN." If not, again add a 50/50 mixture of coolant and water to the expansion tank. Start your vehicle and get it hot... turn it off and let it get COLD. Check the expansion tank level again... Repeat until the expansion tank does NOT go below the "MIN" level.

Good Luck!

[Amechanic]

Now, I bled the air, replaced the radiator cap, but I still get no pressure in the radiator. I don't see any leak in the cooling system. Any ideas? Thanks in advance.

[HeadlessHorseman]

When you say "no pressure" exactly what do you mean? After your engine has been running for 15 minutes, there is definitely pressure in the system, somewhere. Are you saying that, after 15 minutes, your radiator is still cold?

[Amechanic]

Originally Posted by HeadlessHorseman

When you say "no pressure" exactly what do you mean? After your engine has been running for 15 minutes, there is definitely pressure in the system, somewhere. Are you saying that, after 15 minutes, your radiator is still cold?

Yes, after long drive, much more than 15 minutes, it's still cold, actually just warm - not hot. The upper radiator hose can be easily squeezed. I can touch the radiator and take off the radiator cap immediately after the drive. So I assume there is no pressure in the cooling system. I know something is not right. Please help. Thanks

[HeadlessHorseman]

aldovera is correct, I think...

It sounds like the thermostat is stuck in the open or nearly full open position and not regulating coolant temperature as it should. When this happens, the engine never warms up to full operating temperature and the heater never blows hot air (warm, maybe).

What you describe happened to me around 164,000 miles when one of two tiny pieces of metal that hold the plunger on the thermostat in alignment broke and would not allow it to properly close.

The temperature guage never rose to the halfway mark (it's usual position) and on REALLY cold days (like 5 degrees), it barely moved at all above the bottom line.

I drained the coolant from the radiator into a nice clean can, replaced the thermostat, filled the radiator back up and haven't had a problem for over 4 years.

P.S. Nice avatar... I am an Ohio-born Buckeye myself.

[Amechanic]

I already replaced thermostat which fixed the cold engine problem. What I have now is simply a flat upper radiator hose. I have normal engine temprature gauge, hot air, but the presure in the radiator. Is it normal to have no presure in the radiator? Thanks