Bleeding RRC wonky temp gauge

[Jake1996D1]

So when I first got the truck I put in a new radiator and t-stat and the truck has been running little less than half on the temp gauge.

Then the other day I notice it's 3/4 of the way but it wasnt going up or down just hanging out at 3/4. so I pulled over at a gas station let her it for a min.. Then went on with driving.. Still at 3/4. Go and have dinner with the gf and went to drive it home and then it would only go about 1/4 on the gauge.. So I'm thinkin WTF? must be air in the system or the gauge must be bad.

Reason I thought it was air is because I can hear the coolant sloshing/flowing behind the dash. But it was like that since day 1.. Tried to bleed it and it's still there.. Maybe a headgasket issue, but I dont see any other syntoms? maybe I need a special bleeder tool?..

Of course now I cant get it to get above 1/2 on the gauge to trouble shoot..

Thoughts? Anybody else have a hell of a time bleeding an older RRC?

Getting this sorted is the only reason I am aprehensive on pulling the trigger on some FJ80 axles for it..

 

[az_max]

The best luck I've had with bleeding the system is to a) make sure the thermostat has that little bypass hole with the jiggler thingy in it. b) remove the expansion tank cap and the brass plug on the heater pipe ( on top of pass side valve cover). slowly pour antifreeze/water mix in.

 

[Jake1996D1]

I don't have a bleeder screw in mine.. T-stat had jiggle pin and installed correctly. Drive it on the highway again today and it sat low on the temp gauge again... The hoses seem hotter than the temp gauge shows compared to my D1..

 

[Flyfish]

Any changes it coolant levels? You try swapping temp sensor? Do you have flow when you remove the radiator fill plug? Not sure about the older rrc's but i've seen the throttle body warmer gasket on bottom of plenum go bad and mess up the flow.

 

[Jake1996D1]

Any changes it coolant levels? You try swapping temp sensor? Do you have flow when you remove the radiator fill plug? Not sure about the older rrc's but i've seen the throttle body warmer gasket on bottom of plenum go bad and mess up the flow.

I have not tried a different temp sensor yet. coolant levels seem fine but I really have drove it all that much as I work from home. You think air could be getting sucked in thru the throttle body warmer? or hoses maybe? I'll look into it.. I have good flow

 

[kk88rrc]

Reason I thought it was air is because I can hear the coolant sloshing/flowing behind the dash. But it was like that since day 1.. Tried to bleed it and it's still there.. Maybe a headgasket issue, but I dont see any other syntoms? maybe I need a special bleeder tool?..

Of course now I cant get it to get above 1/2 on the gauge to trouble shoot..

Thoughts? Anybody else have a hell of a time bleeding an older RRC?

Here's more or less the process I have used. I did not bother to make the funnel since I had one that fit tightly into the radiator. In addition, I raise the front right corner. I also leave the heater off until the T stat opens then I put the heat on high.

"To begin with, let me describe a little tool I made years ago. Go to Home Depot, or the hardware store. Buy a 6" plastic funnel, 1/2" MPT to 1/2" female PVC tubing fitting, and a small can of PVC cement. Cut the small end of the funnel til you have a good fit of it, into the tubing end of the PVC fitting, and cement it. Now, you have a 6" funnel which screws into the radiator fill plug bung.

Start this whole process on a cold engine.

As the heater core is slightly higher than the top of the engine, elevate the front of the car a few inches. Screw the funnel into the top of the radiator, SLOWLY fill it till it's full, AND the funnel is full.
Start the engine, and let it run, at idle only. It's going to run for several minutes, maybe 8-10, until the thermostat opens. When it does, you're going to see some BIG bubble belch up through the funnel, and the level in the funnel is going to drop. KEEP THE FUNNEL FULL. More ond more bubbles will keep coming, some fluid may spill over, but at some point, the level in the funnel is going to drop ALOT. That's when the air pocket finally made it's way to the radiator. Leave the engine running, with the funnel filled for a good 15 minutes.

Never at any time during the process rev the engine. This will only cavitate the pockets of air, some likely to be in the top of the pump housing, and you'll spill the funnel over and induce more air into the system. Key thing is to keep the funnel full, this keeps air out and a slight hydrostatic head of water to slowly drain into the radiator as it displaces the escaping air.


To finnish it off, shut the engine down, unscrew the expansion tank cap, fill the funnel and let it drain into the expansion tank, close the expansion tank, remove the funnel and cap the radiator. BTW, the expansion tank cap was ON during the running process."

 

[Flyfish]

You think air could be getting sucked in thru the throttle body warmer?

No, it may just disrupt the normal circulation and be harder to bleed properly. First I'd swap temp sensor, that's easy and cheap. To check TB flow, remove rad fill plug, you should see the 1/2" return hose from TB flowing. (on newer rrc's anyway)

 

[Jake1996D1]

Thanks Kevin that is what I do to a T - minus the PVC pipe deal which sounds cool. maybe I will try to bleed it again tomorrow one more time for the hell of it. I havent had any fluctuation in temp yet.

Flyfish - I'm with ya on the temp sensor.. The throttle body heater is-a flowin..

 

[kk88rrc]

'88s do not have a throttle body heater IIRC

If it appears to be a stubborn air lock... I have revved the engine very gentle to coax it a bit but will let it run longer to make sure all the air is out. I used to bleed the system all the time while I was HG denial.

 

[Jake1996D1]

'88s do not have a throttle body heater IIRC

If it appears to be a stubborn air lock... I have revved the engine very gentle to coax it a bit but will let it run longer to make sure all the air is out. I used to bleed the system all the time while I was HG denial.

Mine has a throttle body heater runs to the same spot as a d1 etc.. I would be surprised if it was head gaskets but it runs cool and fine 90% of the time.. Going to take it for a longer trip this Sunday. Wish me luck!

 

[Jake1996D1]

I think my t-stat is sticking.. It went back to running great for a long while. Then the other night gauge went up. Upper hose and radiator was warm but not hot and I couldn't feel water circulating. Got a replacement stat going to give that a try.

 

[RoverDude]

When you notice it getting hot turn the vehicle off then back on. If it goes from hot to warm immediately, it is probably your temp gauge at the cluster going bonkers. If it stays hot, put an Infrared Temperature Gun on crucial spots of the motor. If the temps are fine according to your gun, again your gauge or sending unit. The 87-88 temp gauges were known to have a mind of their own.

 

[Jake1996D1]

When you notice it getting hot turn the vehicle off then back on. If it goes from hot to warm immediately, it is probably your temp gauge at the cluster going bonkers. If it stays hot, put an Infrared Temperature Gun on crucial spots of the motor. If the temps are fine according to your gun, again your gauge or sending unit. The 87-88 temp gauges were known to have a mind of their own.

Thanks John! Should have it all back together at some point this week. Valley gasket was leaking again which may have caused air to get in the system as well.