Overflow tank never changes...

[midfat]

^^^^ We want to be careful NOT to use fluid migration as a diagnostic tool for the condition of your cooling system.

As I alluded to earlier, there are really only two reasons you WOULDN'T have a coolant exchange between the overflow tank and the radiator (assuming the system is full and all air evacuated).

1. The temperature (read pressure) simply is not reaching a point that it overcomes the spring pressure on the radiator cap.

2. The cap is faulty (though faulty radiator caps tend to be 'weak' and not stuck closed).

IF condition #1 is present....this MUST be verified by taking an accurate coolant temperature measurement.

IF condition #2 is present....replace the cap. IF the cap is weak it isn't providing the pressure necessary to prevent the coolant from boiling at a lower temperature than is desireable. IF the cap has somehow failed in a manner such that it can not open (not likely but possible), then excess pressure can occur in the cooling system....resulting in undue stress on certain parts.

Item #1 can easily be determined by taking a reading on the coolant system (I have a ScanGauge and can monitor it all the time). NO harm in having a cool running engine.

Item #2 is best resolved by means of 'prevention' (just replace the darn cap every 2-3 yrs.) and NOT by means of 'diagnosis' (read....you already have problems).

OBDII reading straight off the coolant temp sensor is 185* running temp on extended freeway driving. It fluctuated up to 189* momentarily when I came to a stop in traffic, but within a minute or two, it pulled back to a stable 185*. I can't seem to get to to go above that, which I see as a good thing.

 

[flintknapper]

OBDII reading straight off the coolant temp sensor is 185* running temp on extended freeway driving. It fluctuated up to 189* momentarily when I came to s astopnin traffic, but within a minute or two, pulled back to a stable 185*. I can't seem to get to to go above that, which I see as a good thing.

^^^^^^^ Yes Sir, I agree.

 

[Dave 2000]

Note the cap has two valves, one for pressure lift (expansion), and the other pulls down when the system cools (contraction), you would not be the first with the wrong cap, check you have the two valves.

My expansion tank level goes up and down around 1/2 from stone cold to hot and them cold again, my system is cooled by an electric fan, the movement is the same as when I had a clutch fan.

I do not think you have any problems, but would add the system should be filled with the heater set to hot, and note the heater valve only activates when the ignition is on, so ignition on heater control to hot and then ignition off then fill slowly.

regards

Dave

 

[midfat]

Looks like the system needed to settle in a bit. Perhaps there was some air that needed to find it's way out. Drive it today and now I'm getting about a one inch swing in the expansion tank between stone cold and full temp. Looks like things are about perfect. It was probably all the minerals in the tap water from the flush with the garden hose.

 

[flintknapper]

It was probably all the minerals in the tap water from the flush with the garden hose.

^^^^^ NOT!

 

[chap79]

Perhaps park nose up and lift the front passenger side of your truck some while it is hot to help any air migrate up towards the cap. When I've flushed mine in the past this has help quite a bit.

 

[Tools R Us]

Yeah I wouldn't use tap water to flush. You'll never get it all out. Only flush with distilled. 99cents a gallon, not expensive.

What type of pump do you use to get the pressure needed to fully flush the system? It often takes time, like 10+ min of full blast hose running to get it clean, that is a lot of bottled water. Unless your tap water is really bad, a drain a fill or two will get it out, for most, likely not needed, a small fraction of tap isn't going to hurt anything.

 

[Tools R Us]

Perhaps park nose up and lift the front passenger side of your truck some while it is hot to help any air migrate up towards the cap. When I've flushed mine in the past this has help quite a bit.

Or just drive it a couple of short drive, heat and cool, cycles? The system is designed to get air out, will do it on it's own. The only slight caution is; be easy on it, don't over stress the motor while the system has air in it.

 

[midfat]

For the flush, I put hose into the upper radiator hose and Pulled the lower radiator hose for our flow - heat on full, engine idling for about 20 mins. Once everything was running totally clean, I shut it down and drained the block. Reconnected the upper/lower radiator hoses and refilled with distilled water and 50/50 mix. System was pretty clean to begin with, so good enough in my book.

 

[chap79]

Was the rear heater on too?

*Because someone will ask

 

[midfat]

Was the rear heater on too?

*Because someone will ask

What rear heater?

 

[Formulaonehd]

If the coolant level in the radiator expansion tank doesn't start to rise within 10 minutes after starting the engine... or lower a few hours after shutting down the engine, the radiator cap is faulty.

The cooling system will be overpressurized when the engine is running if the cap doesn't bleed pressure which risks blowing a coolant hose or even worse...the head gasket

can that be the same case for blowing an oil cooler gasket as well ?