open loop idle and temp issues

[uuc328]

So I'm having some weird idle and temp issues on my 85 eta but only when up to operating temp. No flucuation just high idle right at 1000 and temp gauge at 3/4. RPMs were higher, about 1200, pre thermostat replacement.

Radiator, water pump, hoses and t-stat are all new, the cooling system has been mostly overhauled, only sensors remain. It is entirely possible that the thermostat is the wrong temp, picked it up from autozone.

Cleaned the AFM, TB and ICV and am 99% sure there are not any vac leaks.

I don't trust the cluster temp gauge, even with the ground nut snug it isnt very consistent, gets stuck at full cold unless I tap the dash and it also dances around a little once the car is warm.

As expected idle increases when the ICV is unplugged, the same goes for the 2 prong sensor (temp switch?) on the thermostat housing.

cliffs: high idle and temp when warm, not sure what else to do.

[Gregs///M]

I'd start with a new coolant temp sensor. The temp gauge can be remedied by replacing the batteries in the SI board.

Temp gauge should never reach 3/4. 1/2 max. Keep bleeding your cooling system.

[uuc328]

^ Thanks

I'll bleed it again but dont they ususlly overheat with air in the system? I was thinking about trying another thermostat but your suggestion is easier.

SI batteries have been on my list, I'll order a set along with a new temp sensor.

[uuc328]

Bled twice last night but still had temps slightly beyond 12 o'clock on the drive in. it was 30 degrees and an all freeway trip, IMO the car should not even come close getting hot but then again the gauge is flakey. I’m still leaning towards a higher temp thermostat being the culprit for my temp issues. I’ll swap it out and rebleed tonight.

Did some reading and 12631279722 (fast idle temp switch) sounds like the most logical sensor to replace for the high idle. Gregs///M is that the one you had in mind?

[Gregs///M]

Air in the system and leak up toward the sensor giving false reading of hot. A notch or two over the 1/2 way is OK. 3/4 or more is not.

I run a standard 80C thermostat here in California.

High idle is almost always vacuum leaks. I would go ahead and replace the fast idle temp switch.

[uuc328]

Ditched the 80 degree AZ thermostat for a 71 German made part. Rebled and both the temp and idle appear to have stabilized. Gauge is now about a needle width from 12 on the cool side.

[dnguyen1963]

If your car is truly overheating (have you measured the temp with an IR thermometer?) then ditching an 80 t-stat for a 71 t-stat is not fixing the problem. Keep a careful watch on the system for awhile...

[nando]

the 80c t-stat is better than the 71c.

if you've got oveheating issues and the t-stat isn't all out faulty, then something else is wrong. water pump, air in lines, clogged radiator, etc.

[uuc328]

Agreed, i'm not keen on the 71 but it is a better part and I was able to bleed the air this go round.

Don't have access to a thermal gun but I am curious to know what the actual temps are.

Got rear ended on thursday so the car is parked, i'll get a 74 and try to get the needle back at 12 o'clock.

Thanks everyone!

[uuc328]

switched back to an 80 degree, topped off and bled. made a quick drive and i think i'm back to normal. didn't have to muck with any of the sensors after all.

[uuc328]

got her good and hot as opposed to last night's short drive. the temp moved slightly past 12at a long stop light on my way in. might still have a tiny bit of air in there but no where near as bad. no idle issues

[jlevie]

The history in the thread and the latest results suggests that the car might have a clogged radiator and/or bad fan clutch. A fair bit of air in the cooling system is a possibility and you can eliminate that as a possibility by:

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[uuc328]

thanks for the suggestions.
good call on the fan clutch, it was replaced but it was from a parts car. i'll give it another look.
radiator and WP are new and i flushed the system twice, shouldn't be any clogs.
i think i'm stuck in step 5.

[dnguyen1963]

An easy solution to deal with those troublesome air pockets is to drill a small hole in the top plate of the t-stat. This helps bleeding the system much easier.

[uuc328]

1/8 hole was drilled in the 71. bled uber easy but those two combined and the car took forever to warm up.
the 80 AZ thermo has a hole and brass plug thingy on it from the factory.

off to bleed somemore...