I have an odd issue with my 86. New water pump, thermostat, radiator, coolant bottle. I drive about 20 miles to work and the coolant bottle fills up like it's getting hot. The temperature gauge is always low. Is there air trapped somewhere? I put it on ramps a couple of weeks ago to try to bleed it. I've had this truck for over 20 years but I'm baffled by this.

 

It (coolant) is supposed to expand some, its physics, it is also supposed to suck that fluid back in when it cools off.

Things you can check.

Radiator cap (OEM from the local dealership is best), holds the right pressure. (There is a tool/gadget for this.)

Overflow lines are tight (not sucking air during cooldown).

Radiator lines not bulged, or weeping (indicates an internal failure between the layers of rubber).

Exhaust gases in system (indicates a head gasket leak), you can pick up this kit from the local parts store.


Depending on the slope of your driveway, where the air bubbles are ect, a good coolant system burp can take much longer than you might expect. Get the good funnel (bucket funnel by lisel, or similar) designed for this, and let it run for a half hour to an hour monitoring the output.

 

PS, the "always low" temp reading indicates an air pocket on the guage temp sensor(guage temp sensor is located in the middle of the intake area) You may notice high fuel usage due to the ECU always sees the coolant temp as low, as well as an iratic idle speed (this sensor is located at the from of the intake and may give a diff reading).

How is your heat?

 

I have always used the Lisle Spill-Free funnel for burping my truck and seem to have a much easier time than others here without this funnel. Apparently they are making them clear (see through) now, but mine is yellow.

 

All of the above. That burping aid funnel is good, guys! Thanks.
Hopefully not bad head gasket pressurizing the cooling system (I've had the neck of my Civic radiator blown off). While burping watch for violent splashing, not just gurgling from water pump pressure or from escaping air from burping.

 

Yes this and the pressure rating is 13 psi.

 

The cap is new too. I did a head gasket about a year ago. I flushed the heater core a few weeks back that's when I tried to burp it. All I got was small bubbles.I'll try burping again.

 

double

 

I always put a tee in the heater hose.

Fill coolant with the cap off the tee pushes all the air out.

No more trapped air problems

 

Update;
It looks like my new head gasket is blowing into my cooling system. Bummer. It will have to wait til warmer weather. In the mean time I took an old radiator cap and drilled a couple of holes in the inner seal to relieve the excess pressure. It doesn't fill up the overflow nearly as fast. I'm not mixing coolant into my oil but I check it every couple of days. I'm rapidly approaching 300K miles so I may have to consider a rebuild soon. It's sad because it still runs great!