Overheating

Austin__mk3

New Member
Aug 4, 2023
3
0
1
23
Hello, I have an 87 auto trans that overheats in traffic. If I don’t stop but a couple times in a trip I’m fine, but if I get caught sitting at a light for multiple cycles it’ll overheat. I’ve replaced the thermostat, thermostat temp sender( also the sensor under tho forgot the name), radiator, lower rad hose, and rad fan. I don’t know if the engine is really overheating or if it’s a false code from a sensor I haven’t changed. I’m pretty sure the check engine light doesn’t work and that’s why it’s not throwing a code. There’s 3 lights that seem to come on in trifecta: the battery light, brake light, and lights that indicate the taillights. I’m not sure if this has anything to do with the overheating issue as I’ve read it’s either the battery or alternator causing the issue just adding the info to be safe. On my way home today the car didn’t want to pull and seemed to sound different; I think it’s just a misfire so that should be a simple fix. I don’t know if any of these problems correspond to each other so I’m here for advice. The car hasn’t shown any sign of a blown head gasket, no oil in coolant, no smoke. Any advice helps thanks
 

Asterix

Lurker of Power
Mar 31, 2005
461
30
28
Vienna, VA
Since you changed out your radiator, it's unlikely you left any debris between the radiator and AC condenser. This car like to collect leaves there which will block air flow. That said, how clogged is your condenser? That will also block air flow.

Do you have the engine undercover? That will help while idling in hot weather.

Did you change the fan or fan coupler? Does the coupler work? It should makes lots of noise when you start then quiet down, and it should be obviously much louder when the car is hot.

Definitely fix your check engine light first so you can check for codes. It should light when you first move the key to "Run" and before you start the car. I assume you know it only shows codes when you jump TE1 and E1 in the check connector?

As for the other lights acting funny, check your grounds first, especially the on in the rear. Make sure they're not corroded. The battery light means the alternator is not charging, the brake light could be the hand brake is on or your fluid is low, and the taillight indicator means you have a light out or some loose wiring.
 

Bru

Member
Feb 28, 2013
52
30
18
Tampa Bay Area
What is the idle speed at a traffic light? Sometimes when the idle speed is too low, some of the dash trouble lights begin to come on. You could put it in it neutral at a light as a stop gap effort. Typical idle speed for a manual transmission is 650 RPM. With the engine cold give the fan blade a a shove from the passenger side to the driver side. It shouldn't rotate more than 1 /3 of a turn; otherwise your fan clutch could be going out. With the engine cold, look down into the radiator through cap opening the, and see if the cores are plugged up. Remove the 2 upper radiator hold down clamps and take a peek between the front of the radiator and the back of the air conditioning condenser to see if there is any debris clogging up the airflow.