Intermittent Overheating Issue

[noface]

Hey Fellas!

I've got a 1985 4WD Tercel Wagon that sometimes likes to overheat.

It all started with replacing the front crankshaft seal. Everything was fine then. Of course had to remove the radiator to do the job swapping the seal. Got it all back together and it was ok for awhile, and then started running hot.

My son drives this to school everyday 25 miles each way. Called me one afternoon saying water was coming from behind the pump.

I replaced the pump but it was still getting hot.

Swapped the thermostat and radiator cap with new ones from AutoZone.

All is good.

For awhile....

Sometimes while driving down the road, it will swing up towards hot, then back to normal. It will do this a couple times, then stay hot. Fortunately he's kinda trained now to watch for it and doesn't let it get hot enough to damage anything.

The fan comes on when it's supposed to, so I don't think I have a problem there, unless the sensor is intermittent.

It completely fills the over flow resevoir, and doesn't appear to be pulling the coolant back in to the radiator. Once full, it just runs itself dry. And now the coolant is so diluted with water, I'm concerned with winter coming on it will freeze. The antifreeze is just to expensive to keep blowing it out on the ground...

The radiator seems to be fine. It appears to flow well, and the original coolant from the very first drain was a nice green color, and still looks good inside.

I think I've got some air trapped in there, or maybe an intermittent fan sensor?

I dunno... Is there a trick to getting the air out?

Other things to check?

Great car other than this. I just scored a Weber online (used, I'm un-employed and every dollar counts!). Haven't installed it yet.

Recently replaced the TVSV thing, as the original was cracked in half. Got two used from a gentleman here in this forum (THANKS!).

The heater appears to be flowing and works fine....

I've run out of things I know to check...

Thanks!
Jody

[Petros]

Do not assume since you have a new T-stat that is is good. I have had them act like that right out of the box. I stopped buying cheap ones, go for the best you can find (usually about $15, cheap ones are about half that cost, not worth it).

Make sure there are no kinks in the hoses. Can not think of what else would cause that. Air does not tend to get trapped in these cooling systems, some cars do but not so much on the Tercel. The fan sensor would only be an issue if you drive in heavy slow traffic, once moving more than about 25mph, there will be no more cooling at higher speeds.

Sometimes a marginally bad head gasket will run okay, but leak water slowly, you over heat when it runs low. As long as you keep if filled you can keep running it. I drove for a year with a bad head gasket, I just kept filling it every other day. You see steam in the exhaust if it is sucking water into the combustion chamber. But yours does not seem to be acting this way.

Good luck.

[sdoan]

You might also double check the radiator cap. It is designed to have a vacuum tight seal so that when the engine and coolant cool down that coolant is sucked back in from the overflow tank. Might also check the hose from the top of the radiator to the overflow and the straw inside the overflow tank.

The car should push out less than a pint of coolant as it heats up from full cold. If more is being pushed out in one warm up, it may be an indication that it is over heating (due to another cause like stuck thermostat or partially blown head gasket).

Hope this helps.

[noface]

I'll score another thermostat then.

The one I bought was a cheepo from AutoZone.

We don't have a NAPA local, so maybe CarQuest or other independant parts house, as I have a feeling Advance and O'Reilly's are the same ol stuff as AutoZone...

I still have the original radiator cap, and it does the same as the replacement.

Thanks for the tips... I'll post back if/when I get it figgered out!

[Petros]

If I recall, AutoZone had several price point T-stats available. ONe at about $7, one at about $12 and a guaranteed one for $17 or so. Their good one is quality, just take them out of the box and compare them side by side with the cheap one.

[takza]

What I do with all my cars/trucks is to make sure they have a good functioning rad cap....test the hose going to the coolant tank and the clamps on both ends for no clogs and no leaks...pull the plastic coolant tank and clean it out with a hose and high pressure.

Then...I refill the system and the tank up to a reasonable level and drive a few times to stabilize the level. Then after sitting overnite...I use a marker to draw a line on the tank.

After this...I can just look at the tank before starting and know what's going on with the coolant. Both of my vehicles tend to lose a little over time.

One way to test for a head gasket problem (which can cause the coolant tank to overflow) is to take the cap off...start the engine up cold...then look in the top of the rad for a stream of bubbles...which are bubbles of exhaust gas...meaning a gasket issue.

[hberdan]

Are you getting any smoke from the tailpipe? By that, I mean bluish smoke that smells a bit sweet, like antifreeze? and is constant, not intermittant. It would indicate a blown head gasket or worse. Especially if your coolant tank runs completely dry. Check for bubbles in the radiator, as mentioned.

[Crashmachine]

When you install the thermostat check to see if there is a little hole with metal plug in it. You need to install that at the top op the opening. I know matco has this little coolant system bleeder busket that you can put onto the radiator and run the engine to open the thermostat then just wait for the air to stop bublbing out, sometimes it takes awhile. You might be able to find something like that at a parts store. Its a big funnel with attachments to lock onto the radiator cap area.