Guys,

Car: '87 TII

Problem: On the interstate my car runs at about 1/2 on the factory gauge. If the A/C is on it goes up about 3/4 of the "safe" zone on the gauge. As soon as you slow down it cools off. Even with the A/C on and in stop and go traffic it will run at only about 1/3 on the gauge and without the A/C it runs about 1/4, no matter how hot it is outside. It has a MAZDA thermostat and all of the shields are in place. I tried a different fan...same result....Actually I think the fan is more for slow speeds anyway. So.....anybody have any ideas?

Todd

 

Something if blocking flow to the radiator in some way. Remove the radiator and clean it thoroughly. I had a piece of newspaper stuck to mine, as well as some feathers (lol), and other junk. Cleaning it and flushing the coolant solved my higher speed overheating problems.

 

It could be that you are missing the large spring in your lower radiator hose. Perhaps the hose is collapsing at high rpms/speeds.

Could also be your timing is too far advanced.

 

Is it a high RPM only problem? If so, then it sounds like your water pump is cavitating. Either lower engine speed (switch to a higher gear) or install a set of underdrive pullies.

 

it will run a little hotter with the ac on, how old is your radiator?

mike

 

Mike,

The radiator is about 15 years old I guess.

Aaron...I'm already in 5th when it starts to get hot.

Saab...Timing is stock.

I do have a new lower hose that I have been waiting to put on it.

Todd

 

maybe the radiator is plugged

mike

 

I have the same problem right now... when I'm WOT 1-2-3 it gots hot (3/4 on the gauge) so I ordered new thermostat, waterpump, lower rad hose. I hope that will do the trick... is it safe to install a underdrive pulley on a 88 alternator?

 

how the hell did you get newspaper and feathers stuck in there?!

 

He ran over a bird reading the news paper.

RX7Boi....let me know if that solves your problem. I have a lower hose...just put an upper hose on it. I also have a new thermostat. I am WONDERING if I need a water pump.

Todd

 

If your rad is 15 years old, it's time to get that thing serviced. At the same time, replace all your coolant hoses (including heater hoses, and the ones on the throttle body).

 

Do a test on your fan. warm up the motor to full temp and stop the car. Turn the fan by hand and there should be slight to moderate resistance. If it spins freely then your clutch in the fan is burnt - time for a junk yard trip.

 

try getting an underdrive pulley for your water pump. If it ONLY happens at high RPM's, that's the same problem we have on race cars.. over xxxx RPM the stock water pump is about useless, and it just cavitates.

 

The fan has zero effect at speed.
High rpm yes, but not necessarily high speed. In 5th gear, you'd need to be doing a crazy speed for cavitation to be a problem, well over 100mph.

Akageals, you say "on the interstate", but what speeds are we talking here? On a dodgy system (blocked radiator or whatever), the constant high load on the cooling system from constant interstate speed would be enough to push it over the limit. Mazda designed the cooling system to handle constant high speed, so something is probably blocking the flow of either coolant or air.
Don't try to fix something that's broken by modifying something else.

 

I'm talking 55 or above so I know the rpm's are not too high. I have some sort of problem. I too thought the fan would not have much effect at speed, that's why i'm stumped. I don't think airflow is the problem.

Todd

 

My two guesse would be a blocked radiator or a corroded water pump impeller. Remove the radiator and have it professionally flushed and while it's out, remove and inspect the water pump.

 

Ask the previous owner. Yeah bird reading the newspaper sounds likely, lol.

I agree, have the radiator flushed and cleaned, and make sure all the ducting that flows air to the radiator is in tact.

-Brian