Hey guys, i just picked up a 1987 N/A with a BT, its pretty sweet, and I'm absolutely loving feeling boost again! However, Im running into an interesting problem, the motor seems to be running hotter while im crusing on the highway than if im just sitting at a light in traffic. (i.e. on the highway the temp gauge sometimes gets up to about 2/3, then after exiting and immediately getting stopped at a light the car actually gets cooler! Almost back to normal temps.)

I'm wondering what the heck is causing this to happen.... Clogged radiator? Thermostat?

I realize it's summer and I am going to see hotter temps, but the temps at highway vs. city driving seems to me that they should be inverted.

The motor is bone stock, still has the clutch fan and aux. elec fans that actually function. The A/C has been removed. Literally no modifications done to the motor.

Any ideas? Thanks for looking!

 

The stock temperature gauge is pretty inaccurate. I'd rig an aftermarket one up to temporarily monitor the temps and re-evaluate.

 

have you checked to make sure it still has the stock under tray?

it's a plastic piece that goes from the bottom of the bumper to the engine subframe.

 

does it have the shroud?

 

Is your fan clutch frozen? If it can't freespin when warmed up or when moving at high speeds, it will actually be a restriction and will cause less air to pass through the radiator. With as much air as it can pull, it still isn't as much as will enter the grille at highway speeds.

A lack of fan shroud would have the opposite effect as it would overheat sitting still but be fine when moving. The stock undertray can be left off, and although important, will still not cause the car to overheat during normal driving. Especially when not moving. At that speed the only thing that matters is airlfow through the radiator. It could be hidden in the fender but as long as air flowed across it, it would still cool.

 

just trying to get some more info

 

I haven't checked the clutch fan yet, that is definitely a possibility. The under tray is there, the shroud is there, the thing hasn't been touched by human hands except to give it a tune up, lol. As soon as I can fix this no start bug I'll get it warmed up and find out if it is seized or not. Thanks guys!

 

I am having the exact same problem, when i am on the highway the temp gauge will rise when i reach around 65-70mph, if i turn the vent on to heat, the temp gauge will drop back to where it should be.

 

so you have both an E-fan and the stock clutch fan? The stock clutch fan is good up to 250hp i believe, and will not work correctly if your trying to do an e-fan/clutch fan set up.

make sure you dont have any gunk/grass/tar clogged up in the fins of the radiator, ive seen ungodly pictures of just clumps that look like cow poop stuck onto the radiator through all the fins.

*check thermostat
*check coolant level
*check slippage on the clutch fan / how freely its able to move
*check for bubbles in the system.

 

it is possible to have a failing water pump, I had a car that had the same issue, a old timer told me it was the water pump but I did not believe him, sure enough when I took it off the impeller inside was almost all gone

the bearing can also be going- grab the pulley and see if you can wiggle it, if the pump is of unknown age just change it

 

Zeromage, I was referring to the auxiliary e-fan. And I have checked the water pump for slippage and free play, it works fine. I replaced the clutch fan with a known good one, but unfortunately I wont be able to find out if it works until I rebuild the engine cuz the rear rotor just popped (0 psi)

Oh well, I was planning on rebuilding anyway. Mo streetport!

 

How does the oil cooler look? debris? bent fins? I've also heard of the oil cooler thermo going out, but that seems to be fairly uncommon.

Sucks to hear about the rebuilt, at least you've got the opportunity to upgrade

 

With the exception of the rear rotor being popped, this engine and everything with it is pristine... for the price I paid I really lucked out. A few weeks from now I will be running in a mean FC, with a brand new e-fan, lol.