I need some new ideas. My recent rebuild (rebuilt it myself) runs hot. It has yet to overheat but it has been cool here in New England. On the stock gauge it runs 3/4 to 4/5 to the inner high mark. To confirm it was not the gauge I installed an aftermarket sensor and gauge and it runs 190 - 205. On the highway at 70 in 5th it runs right at 195, 70 in 4th and it will climb to 205 or with the ac on. I put 300 miles on it on saturday and it stayed right at 195 the whole time. I've researched and tested everthing I can think of, here's what I've done.

Replaced fan (used, I guess it could be bad as well), cleaned radiator and installed a new 180 thermostat. Set timing, TPS, variable resistor and pressure sensor all using Icemark's excellent posts. The water pump does not leak or squeal and it burns no coolant. Good oil pressure (no oil temp gauge). New O2 sensor. The engine is 1500 miles into the breakin and I've changed the oil 3 times. It idles great, runs strong. All the plastic air funneling parts are under and around the radiator and all foam is in place. 5th and 6th ports move smoothly.

The only ideas I have left are the used fan is bad or the water pump impellers are gone even though the water pump turns smoothly and without leaks.

thanks Jim

 

ps I removed the cats as well to make sure they weren't creating backpressure.

 

did you flush the coolant system? flush the radiator and the engine

 

Did It over heat prior to the rebuild? I'm willing to beat you didn't purge the system of air right.

 

I drained the block and the radiator, ran straight water. Then filled with radiator flush ran that for a week, then filled with coolant mix, ran that for a week and drained and refilled, the second time I added waterwetter. There is definitely no air in the system and I haven't needed to add any coolant after burping the system.

I don't know the story prior to the rebuild the motor threw an apex and the car was given to me. I replaced the rotors and housings and the intermediate housing all of which were bad. I painstakingly measured everything per the turrentine video, haynes and FSM.

 

When purging the system of air, did you first:

-Pour Coolant mix from Thermostat housing and open up the Radiator Bleed Screw to allow Coolant to seep out of their and Immediatly close awhile Coolant was flowing out?

-After step 1., Did you disconnect the top end of the hose leading to the Water Thermo Valve, (actually beside) found at the back of the Throttle Body, and allow Coolant to pour out, thus ensuring that upper area was free from air?

If this still doesn't work, than whats the condition of your Rad? Do you notice after taking your car for a run that your Coolant level has gone down?

 

erm, sounds like your gauge sucks tho. My T2 puts the stock gauge at about the halfway point(exactly horizontal) when my mechanical thermo gauge says 190

 

Sounds about right to me only my stock gauge would read 1/2 at 205-210, on my 88' I had an Autometer gauge right next to the thermostat. hope this helps

 

The thing that sneaks up on you is the fan clutch. On the warmed up series 4 version the fan pulls hard up to about 4k, and then maintains ~4k as the engine revs higher. My 87 was slipping at 2500. You can get the fan clutch to bite better by bending the bimetal strip outward. That should help for a while. I ended up buying a new fan clutch.
When my 91 fan clutch started slipping too much, I pulled it & put in an electric fan.

 

silverrotor, yes all but the water thermo valve I'll do that. But I've put 1500 miles on it so the air must be out of the system no?

From some of the follow on posts maybe I'm not overheating? again it's been cool out but with the ac and 4000rpm I've never gone above 205?

Shouldn't be the fan, which is not even needed at high way speeds and it doesn't overheat at idle.

 

If you have a 180 degree thermostat isn't 195 degree's abot right?? What is the stock thermostat's tempeture rating??

 

A 180 starts to open at 180 and should be at full lift around 200. I would think in cool weather and not pushing it hard it should stay around 180-185. I could be wrong maybe mid to high 190s is normal, but when I was using the stock gauge it sure didn't look normal ie top 1/5 of the inner bracket.

 

The air would still remain In the system. I found the temp readings on my stock and aftermarket water temp gauges remain consistent. ie. 180F on aftermarket, a quarter up on the stocker. I should mention, aswell, that I had damn near Identical problems as you described. So I have, In one shot, went as far as to replace ALL the Coolant Temperture Sensors which Is what Is giving me pristine readings now and when I replaced the old ones. I took the Cooling System that seriously.

If you are to replace any sensors, I'd replace the Coolant Sender Unit found beside the Oil Pressure Sender Unit. Again, after you purge the system of air right.