When I bought my 90 HB Si I noticed that my cooling fan had been hardwired in so that it ran all the time...this morning it was unusually warm for January (13C) and I glanced at my gauges and couldn't believe my eyes when my temperature gauge was almost in the red...with the fan running constant! I couldn't figure out what was going on...the only thing that I'd done different this morning was not turn on the heater...so I tried that...
I opened my windows and turned on the heater full blast taking the air in from over the engine...within a minute my gauge was coming back down and levelled off (with the occasional spike) over the next five minutes.

WTF? Help? Temperature when it comes to my engine is all new to me...so go easy...

Jason

 

Something is wrong with your radiator and related systems. The old owner was probably too lazy to fix it so he just hardwired the fan. First off, check your coolant. When the car is completely cold run it and take the cap off and look to see if the coolant is moving. If not something is clogged or your water pump is junk.

 

could be just the thermostat

 

Check your radiator cap, maybe it isn't holding enough pressure. Check the seal around the cap.

 

Haven't checked yet (at work...will check all of this later)...but the rad and cap were new less than a year ago.

Jason

 

I would get the grease lighting coolant fix stuff, it is called grease lightning ctop leak for the cooling system, jsut pour it all in ur radiator, then top off with water, or antifreeze and start the car and let it run for 5 or 6 mins. It should fix it.

 

Sounds like the radiator is clogged, typical for a car of that age. Remember, the heater is only a mini-radiator inside the car. Turning the heat to full blast has a decent cooling effect on the engine.

Do the cheapest step first, replace the thermosat with a new OEM part.

Running the fan full-time is a band-aid fix. Rewire it to run as normal and fix the real problem.

 

you might also want to make sure you have sufficient coolant in there.maybe you need to top it up and get the air outta the system. When its cold take off the rad cap and look into the rad to see if there is any if you can see any coolant..if not top it up and run the engine a bit.carefully monitoring the rad