Have you verified the actual temp with an ir gun pointed at the t-stat housing? Sometimes the gauges go bad or the sensor.

 

OP said in his first post he's verified with IR gun.

OP what e fan setup are you running? What size tires? Stock gears? Have a transmission cooler?

 

I'm pulling 4700 cfm with both fans. 35 inch tires, 4.88 gears. It started doing this with 3.55 gears and 33's. But it once was fine with that setup. It has stock cooler mounted in front of condenser. And I would believe tranny cooler, but it Overheats in the driveway, holding it at 2500 rpm. No load on tranny. But I do appreciate the pointers. Ty.

 

your profile says you are running a 4.6, but post one here says 4.0. what one is under the hood? the only thing i can think of is your fans arent pulling what they say they are, or stuff in front of radiator is plugged and not allowing airflow. how are the fan shrouds? maybe air is coming around and not though the radiator? how do you feel about hood vents?
your issue scares the hell out of me, i have a 90 4.0 as well and i am getting ready to swap over to an open system with a csf 3 core rad. i have fears myself that my parts arent going to fix the overheating, and then i see your post....... f

 

I was told by po it was 4.6, I don't believe it is. I do have shrouds around the fans. If it was the fans causing the problem, it would overheat at idle and in traffic, and it doesn't. And it does have hood vents now. Everything I have done has had very minimal effect on cooling. Basically it is a driveway queen.

 

Given all the new components and the fact that it only overheats under load regardless of it moving or not, I'd say your problem is that half of your engine is basically dead. 3 out of 6 cyls running at 40 psi is causing excessive heat build up. Time for a swap with a HO.

 

Kalali, I have been trying to fight that. Because how good it runs, and just passed smog, but I think it may be the truth.

 

Another compression test wouldn't hurt... Maybe you got bad readings on the first attempt?

 

Have you checked your transmission? Does the lines run through the radiator? If so it could be transferring its heat on to your system. Also have you check to make sure your T-stat is properly working?

 

Take the air restricter out of your air intake & also check your MAP sensor that it still good. I'm having the same problem & was told today to check these things. Also to move your air temp sensor to the air box it read cooler.

 

I have a 88 5 speed and I took out the restrector and try and run under 2000 rpm's with the ac on in 102 heat 100 miles for work today and stayed between 210 and 230 but when back down when stopped in LA traffic

 

. What about the cap on pressure bottle has it been replaced. Theres a cap upgrade that can be done .
.

 

I second that. With such low compression readings you should have rough running, etc.

 

Didnt have a chance to mess with the heep this weekend. But i will keep everyone updated on the progress.

 

there is also one thing that i found out with mine , is that you can get a head gasket leak into the exhaust manifold that will cause it to run hot quick..so hot that it would puke back pressure into the overflow bottle. 200,000 miles, i just put in new head and all the trimings. so far so good.