1987 overheating - Toyota Nation Forum : Toyota Car and Truck Forums

Montanahelp · 07-07-2007, 12:37 AM

I have a project car (4 cylinder) that it running hot. At highway speeds it hovers around the mid point range on the gauge, but the gauge wants to climb after about 15 miles. If I turn the heater on it cools to the mid point on the gauge at highway speeds. The slower I go the hotter it runs. It jumps to the high side very fast. ITS STRANGE HOW THE GAUGE REACTS SO QUICKLY. I have replaced the water pump, and today the thermostat, but it still runs hot. I thought the gauge wasn't working properly, but the water was boiling when I parked it after about.40 miles. Both cooling fans are working, Tomorrow I am going to swap the radiator with one from a parts rig. I don't have any steam out of the exhaust pipe or any moisture in the oil.

66conv6 · 07-07-2007, 08:41 PM

I had a similar problem in my 88. It was a POS (previous owner syndrome). New radiator for $120 solved the problem. Also I use Toyota hoses, water pump and thermostat as they are better quality then aftermarket. Now can't get number 2 fan for A/C to come on most times. Temp gauge goes way up in city traffic (110 degree heat) with A/C on.

atobe · 07-07-2007, 08:58 PM

check your thermostat ... may be also time for a coolant flush

Kingdom934 · 07-07-2007, 10:27 PM

Sounds like the coolant is going bad. Drain and flush it. 50/50 mix if it isn't the 'premix' coolant.

Mike Gerber · 07-08-2007, 11:19 AM

I have to agree with 66conv6. Sounds like a partially clogged radiator. It can cool the engine under light duty conditions, but when that extra heat is added to the engine by driving at sustained highway speeds, it can no longer adequately dissipate the heat produced. This is the most common cause of the symptoms you describe. I would try that other radiator you have, if you are sure it is good. You might want to take that second radiator or the radiator on the car now in to a radiator shop and have it flow tested.

Mike

***toyomoho*** · 07-11-2007, 02:38 PM

If the heater cools things down and its use is required at hwy speeds, the radiator has very little extra cooling capacity. Could be plugged, inside or out. Is the air dam in place below the radiator (if this car has one)?

Montanahelp · 07-13-2007, 11:49 AM

I changed the radiator with a used one that I had. It was running cooler, but the gauge climbs when I slow down. I unplugged the fan temp sensor (mounted on the thermostat housing) which makes both fans run all of the time which helps, but it is just a bandaid. So far I have changed the thermostat, waterpump, and radiator.

When I turn off the car after being up to temperature, I can hear the radiator bubbling.

Another thing is that when I drive from a cold start it it gets up to normal opererating temperature within 2 miles. It seams way too fast to get to temperature.

I'm afraid I have a headgasket bad. How can I tell if that is the case?

Kingdom934 · 07-13-2007, 02:04 PM

If there's bubbling, there's air in there.

Bad headgasket symptoms are usually the milkshake sludge under oil cap, Smokey exhaust (not to be confused with morning smoke), and it is eating coolant.

Mike Gerber · 07-13-2007, 04:10 PM

I agree there might be air in the cooling system. Try a thorough bleeding of the system. Raise the front of the car slightly (the slightly raised incline of a driveway should be sufficient) and then remove the radiator cap. Now start the engine and let it idle for 45 minutes to 1 hour. You should see some bubbles rising through the radiator neck.

Mike

atobe · 07-13-2007, 09:07 PM

or you can just run the car w/o the rad cap for a few mins with the heater on full blast that should bleed the system...make sure there's hot air comming out though.