Coolant always cold - but normal temperature

It depends on the vehicle. Many gas use a 193 thermostat. It would be nice to see numbers.

Take the radiator overflow tank out of the rig and wash it out. Most likely what you're seeing is not coolant but crud/rust in the tank.

If that's not the case, then the radiator is not sucking the overflow coolant back in when you cool down. This can be caused by a bad rad cap or a plugged or leaking pickup tube.

Bodo,

Please share with us what coach/chassis you have.

Is the reservoir you are checking an integral part of the cooling system or an overflow reservoir?

Does the level in the reservoir change between cold (before engine started) and just after you shut it down (engine hot)?

And, with a pressure cap, coolant should NEVER boil. The function of the pressure cap is to raise the boiling point. Same for coolant-- the correct 50/50 mixture boils at a higher temperature than plain water.

wolfe10 wrote:
Bodo,

Please share with us what coach/chassis you have.

Is the reservoir you are checking an integral part of the cooling system or an overflow reservoir?

Does the level in the reservoir change between cold (before engine started) and just after you shut it down (engine hot)?

And, with a pressure cap, coolant should NEVER boil. The function of the pressure cap is to raise the boiling point. Same for coolant-- the correct 50/50 mixture boils at a higher temperature than plain water.

It is a Fleetwood Fiesta 2006 - Workhorse Chassis W16
It is an overflow reservoir as I understand.
Orange Dexto Cool is inside, was always at level COLD, now after 3 months parking the level was a little bit under COLD (just a few millimeters). Beside the coolant there was also some black dirt inside that tank, some mixture of oil/grease/sand I guess. I opened that reservoir today, cleaned it and have add new coolant (50/50) into it.
I filled it to about 1/2 inch above the COLD mark.

Still, when I start the engine and bring it to normal temperature (takes about 2 minutes), the level in that overflow tank is always the same. It never rises to HOT.
But the manual says, that the level should be HOT when the engine is warm.

BTW: I also opened the pressure cap when the motor was cold (or I tried, as I wasnt able to open it completely) and some liquid came out there (very slowly). I closed it then.
I never see any liquid under the RV, its not loosing anything.

You may have an air bubble in the radiator that is taking care of the expansion of the coolant.
The plastic tank is an overflow tank and is used to take excess coolant out of the radiator when the coolant is hot and allow it to suck back in to the radiator as the coolant cools down.
If there is any air in the radiator, it will not function as designed.
The normal operating temp of your coolant is around 200 degrees so driving through 117 degree heat should have a negligible affect on a properly operating cooling system.
You have an electrical cooling fan in the front of your radiator that comes on with the AC unit when the temperature increases in your cooling system.
There is also a fan clutch that will lock up your engine driven radiator fan when your coolant temperature reaches 107-110 degrees. This may only happen during a steep climb.
You should have been able to take off the radiator cap with the engine cool. You may have to press on it while turning it. It is probably a 15 pound pressure cap.

I'm gonna go with a hole in the pickup tube that is stuck down into the overflow tank.

Yes, you have a problem if the level in the overflow does not change between cold and hot.

As suggested, air in your radiator can absorb the expansion as coolant heats (the most likely reason). But, if removing the radiator cap with the coolant cold shows coolant in the neck (no air) that is not the probable cause.

You can pull the hose out of the overflow reservoir and off the radiator neck, suck on one end with your finger over the other end to verify that the hose is OK.

wolfe10 wrote:
Yes, you have a problem if the level in the overflow does not change between cold and hot.

As suggested, air in your radiator can absorb the expansion as coolant heats (the most likely reason). But, if removing the radiator cap with the coolant cold shows coolant in the neck (no air) that is not the probable cause.

You can pull the hose out of the overflow reservoir and off the radiator neck, suck on one end with your finger over the other end to verify that the hose is OK.

you mean to check if there is a hole in that system? but wouldn the coolant then just spill out somewhere under the RV?


I will try a longer drive tomorrow and see if the level changes. At least today we recognized a change of lets say 1/2 inch after the motor cooled down again.
But - the coolant in the overflow should be warm I guess, but it isn't.


So anyway, do I have a problem of overheating the engine now at this point? I would have never recognized that problem so far, normal temperature, AC works, heating works. Just as I began to think I should one day check that coolant level I thought: Shouldnt that be warm after driving...

The coolant in the overflow bottle really never should feel very warm. What is in the bottle is generally cool and the little over flow from expansion quickly mixes and won't feel very warn to the touch. Sounds like your coach is just fine.