Burping the coolant

[retorq]

What temp thermostat do you have in there??

 

[SunlitComet]

K I did the jack up the front method but the coolant didn't seem to go down at all. I will try sunlitcomet's method next time I get a chance. The only reason I suspect air still in the system is because when the truck gets up to operating temperature it will remain that temp and then randomly it will go up to about halfway, stay there for 20 sec and then go back down...How will I know if my reservoir isn't working properly?

Based on that I could tell you your truck seems to be operating just fine although it shows some lag in your fan clutch engagment. In the reservoir if the hose or fitting that comes off the cap into the tank is broke or cracked it would obviously dump excess coolant in the tank but during cool down it would suck some air since there is an opening above the coolant line. Use a vacuum pump on the rad overflow hose while plugging the end inside the overflow tank after purging the line of collant and see if it holds a vacuum. If you can try this to test your clutch:

1. Start with cool engine to ensure complete fan clutch disengagement.
2. If fan and clutch assembly free wheels with no drag (revolves more than five times when spun by hand), replace clutch. If clutch performs properly with slight drag, proceed to following step.
3. Position thermometer so it is located between fan blades and radiator, noting the following:

1. Insert thermometer sensor through one of existing holes in fan shroud or place between radiator and shroud. It may be necessary to drill a 3/16 inch hole in fan shroud to insert thermometer.
2. Check for adequate clearance between fan blades and thermometer sensor before starting engine, as damage could occur.

4. With thermometer in position, cover radiator grill sufficiently to induce high engine temperature.
5. Start engine, then turn on air conditioning and operate at 2000 RPM.
6. Observe thermometer reading when clutch disengages, noting the following:

1. It will take approximately five to ten minutes for temperature to become high enough to allow engagement of fan clutch. This will be indicated by a 5-15 degrees F drop in thermometer reading.
2. If clutch did not engage between 150-195 degrees F, unit should be replaced. Ensure fan clutch was disengaged at beginning of test.
3. If no sharp increase in fan noise or temperature drop was observed and fan noise level was constantly high from start of test to 190 degrees F, unit should be replaced. Do not continue this test past thermometer reading of 190 degrees F to prevent engine overheating.

7. As soon as clutch engages, remove radiator grill cover and turn A/C off to assist in engine cooling. Run engine at approximately 1500 RPM.
8. After several minutes, fan clutch should disengage as indicated by reduction in fan speed and roar. If fan clutch fails to function as described, replace it.

 

[alanb]

I have the same problem after fitting a new rad and water pump, when the system is up to temp the excess fluid finds it's way to the expansion tank, but when it cools the vacuum in the rad should suck fluid back from the expansion tank to the rad, but it doesn't, so I suspect it's sucking air from somewhere else, just need to track it down.
Anyone have any ideas where ?

 

[SunlitComet]

only a rubber hose between the rad and tank so take it out along with the reservoir. plug the open end of hose. fill it up and leaks for leaks and bubbles.

---------- Post added at 06:13 PM ---------- Previous post was at 06:11 PM ----------

Actually the rad cap plays a role in that to so maybe get that tested too.

 

[alanb]

It was the rad cap that was knacked, I tested it by blowing into the outlet for the expansion tank and could hear and feel air coming past the cap, tried another one and no air leak, the cap looked ok but was not sealing, so as the coolant cooled air was being sucked in to the rad instead of coolant from the expansion tank.
That's another job done

 

[AtomicHoe094]

nice. at least you found the problem!

 

[longstand]

K I did the jack up the front method but the coolant didn't seem to go down at all. I will try sunlitcomet's method next time I get a chance. The only reason I suspect air still in the system is because when the truck gets up to operating temperature it will remain that temp and then randomly it will go up to about halfway, stay there for 20 sec and then go back down...How will I know if my reservoir isn't working properly?

This is not a JOKE!!!!

Jack THAT Front END. Really really HIGH. then Run your Engine. let it warm up, Then FILL it up. Let it RUN for about 5 Minutes. Stop. Let it COOL off. Do it again until its FULL..

It work for me. Always Work for me.