Can't keep the in town temp. down. Replaced both cooling fans, bypassed the relays and installed manual switches inside to control fans, bled air out of system, and it still over heats, temps as high as 250 260, but only in the city. Rads been flushed, system pressure tested, now frustrated and ready to shoot my baby in the block...

 

I guess it's time to pull the radiator...unless you already have.

What does the digital temp show?

 

radiator was out have to go by the digital gauge. However, it only does it a low and idle speeds. Just had it on the highway, temp did not go over 204, but as soon as I stopped, the darn thing started rising in temp pretty darn fast.

 

That leaves as possible ....water pump going out or radiator cap not holding pressure, but I think you checked those also.

Have you pulled the knock sensors?

 

hey viscount why must he pull the knock sensors ... im wondering because i have the same problem . i had the tank blow up instead of a cheap hose and it took out my lower right fender as well when it blew , im think it was rad cap tho... but im wondering why remove those sensors?

 

The FSM advises pulling the K/S as they are the lowest point in the block & accumulate quite a bit of residue.

A few guys on this & other forums have reported having to use screw driver the break the gunky stuff loose after pulling the K/S.

 

Hay guys ,What the hell is a Knock senser? I have the same overheat problem on my 87 corvette. Heats up at idle and low speeds. OK on Highway. Do I have a knock sensor on my87 Vette? I have checked the w/p replaced the thermostat, flushed the radiator,chang ed the pressure cap checked the cooling fan. All to no avail.
Someone advised that i purge the air from the radiator. I tried this but when I remove the pressure cap the coolent pours out. Help!!
AWDCO

 

Not familiar with 87 engines...don't know about K/S.

 

This just educated guess but have you checked your temp sending units? I once had a similar problem on a Trans Am. Gauge would read hot when idling but no other overheating symptoms at idle. traveling down the highway temp would drop to 210 or so. changed almost every part of the cooling system most with hi po aftermarket parts. put in a aftermarket manual gauge cluster and it read 180 to match the thermostat. idle goin down road period. so i removed this and installed a new sending unit. 180 on factory gauge. if u not checked this might be worth a try.

 

Its the round sensor located just in front of your started solenoid on the side of the block, it has a single wire connector. It detects detonation/preignition and allows the ecu to adjust timing accordingly. It;s been a while but Im pretty sure its also in the same spot on a LT1