engine overheating problems

[ramble01]

new to post, and not a mechanic, I've been having problems with high temperatures and have been blowing head gaskets. latest one was a re manufactured engine after 35,000 miles, anyway the temperature gauge is all over the place and has always been that way, often above halfway. I replaced the water pump when the new engine was put in. Its got a Weber carb. I think the temperature was high before I added the Weber, but I can't remember. so I had the radiator flushed, put in a new radiator a double core, put in a new thermostat (from Toyota)(185 degrees I think) this works a little better but its still basically the same. lately I noticed I could get the temperature gauge to drop if I revved the engine heavily (above 3000 rpms always) I took surface temperatures of the engine 209 degrees - 236 degrees in the area around the thermostat, when its running hot. Is this too hot? What kind of temperatures should I be getting? I am about to change the radiator fan sensor but there are two models for the 3AC one that turns on at 179 degrees, and the other turns on at 191degrees. the latter is actually the one that could easily be plugged in (it has two electric wires) the lower temperature one could be installed with (so says my mechanic)- with a little futzing. Should I go with the standard one (191) or try out the lower temperature one. Please help I love these cars, and haven't found any better.

[sdoan]

I would expect that the engine block would not be more than the water temperature (200-215 degrees F) except right around the exhaust manifold.

Does your current radiator fan work?

With a rebuilt engine, new T-stat and new radiator you've covered the big stuff. Have you changed the water pump as well? Any chance you are running the car low on water and then having it over heat? The variations in the temperature gauge suggest an air pocket to me.

A slow leak can slowly lower coolant in the engine over days or weeks of driving, and if you have a bad radiator cap or hole in the straw from the overflow tank you might see enough coolant in the overflow tank and yet be low in the engine. If you pull the radiator cap off cold (don't do it hot or it could blow hot coolant all over you!) it should be full up to the top. I always park the car front up hill when doing this so the radiator cap is the highest part of the cooling system.

A way to test if the cooling system is full hot is to squeeze the top hose (it will be quite warm). If it is firm the cooling system has built up pressure and is pretty full. If it is not firm there is some airspace and the top hose will be compressible.

Slow leaks that might be hard to spot are around the water pump, the bypass tube near the water pump (there is also a water pump o-ring on the front of the block that is under the timing belt and cover), the heater hoses, and the steel heater feed pipe that runs below the manifolds and the heater core itself (although you'd smell coolant as the car warmed up, and it would probably fog your windshield).

Other things that cause over heating are a blown head gasket (sometimes they fail just enough to over heat a while before they really blow out), really bad timing or a really lean mix. Timing and mixture problems would present drivability problems and cause pinging. Only other things I can think of are dumb stuff like installing the thermostat backwards which I think is impossible.

[takza]

Sometimes you get an exhaust into coolant leak...test this by starting the engine cold...remove the rad cap and look for a stream of bubbles...this can be very few bubbles or much worse.

When I used the OEM fan switch...the fan would never come on except for when idling offroad on a hot day.

[Petros]

That is too hot, max should be about 210. The fan sensor will not help that. When the car is moving the fan never comes on anyway, not likely the fan switch will fix it. check to make sure your lower rad hose does not collapse when you rev the engine (make sure it is fully warmed up with t-stat open), sometimes the hose is not stiff enough to stay open when the engine is reved.

It is also not likely to be the water pump. It either works, or it is failed, and leaking all over the place.

In my experience fluctuating temp is usually the cause of the T-stat. Do not assume because it is new that it is good, I have had new ones junk right out of the box. Best to get a quality one, either toyota OEM or get the top quality NAPA one (usual about $16 or so, cheap ones are about half that, and not worth it). Even with a good one they only last about 2-3 years, so expect to replace it regularly. If yours is truly a Toyota t-stat than I would expect it to be good. Did it act this way before you put in the new t-stat?

With a new cap, new rad, no leaks and properly working t-stat it should run just below half way on the gauge, and hold steady. Even with a bad head gasket, as long as there is coolant in it, it should stay cool. I drove mine for a year with a bad head gasket, I just top up the rad every time I got gas.

It is possible you have air trapped in the block or head? I have had this problem with other cars, but not the Tercel. Sometimes you get trapped air and it is diffult to fill all the way without bleeding the block.

good luck/

[ramble01]

thanks for all the ideas. it is really appreciated. I haven't been able to get any work done on it yet. I know the radiator is good. also the thermostat is brand new and toyota brand, and the coolant level is steady. the carb mix had been made richer already so its probably not that. the rad fan is probably not it because it gets down to below halfway when the engine is revved above 3500 rpm. (which is killing my fuel economy) so the problem seems to be with water flow or air. so we will back off the timing ( my mechanic always goes for max power). and check for exhaust in the coolant to see if maybe there is a secret crack in the engine, because the head gasket is brand new. maybe the water pump was bad from the get go (or just not efficient) it was installed 40,000 miles ago when the new engine was installed (because it's run hot that whole time but has gotten worse this past year) is there a highly recommended water pump for these engines? we'll pop the cover off the one on there now and see what's there and if there are any options for a better, more efficient,pump. I'll keep you posted on how it turns out.

[Highlander]

Why are you so certain that the radiator is good? I was convinced of the same thing with my '85 , which was always reading high and boiling out water when in heatsoak. The rad always felt hot when it should have, so I convinced myself that it was fine. I finally changed out the radiator with a new one from the '83 and voila! no more high temps. When I pulled the radiator, it weighed about 3lbs more than the clean one that I put in-there was enough goo in it to choke a horse! , of course it came from a farm in Wyoming, so it probably had the rad filled with trough water time and again . So the moral of the story is, don't take anything for granted, just because it feels hot to your hand , doesn't mean that its working to its fullest capacity. JMHO

[Petros]

Highlander,

You can usually save a radiator that is clogged with crud, you have to flush it and use harsh chemicals to clean it out, but it can usually be done. As long as the metal is not too badly corrorded away, it will be usable.

[4wdchico]

I had a very similar issue that drove me nuts with my FS Bronco. New triple row rad, two new t'stats & pressure testing and ect.& ect...

Turned out to be a bad impeller in the water pump. The cheesy aftermarket waterpumps often have a whimpy stamped impeller. So I'm suggesting that you pull the waterpump and take a look at it's impeller.

Yes it is a rare problem, but when you have tried everything else...

[hberdan]

I've had all kinds of minor overheating issues with Tercels; I don't think the cooling system is rugged enough for the demands placed on it. I've replaced radiators on all three of my Tercels at one point or another; the old OE ones were rotted out. Like the thin sheet metal Tercel body, the radiators must've been designed with thin thin tubing to save weight, maybe.
I've replaced every cooling system part on my current wagon at least twice now; radiator (first replacement was defective, warranty replaced), radiator fan (once), water pump, all the hoses, thermostats, etc. Everything but the darn heater core, which is a true puzzle to replace. And it has a pinhole leak, I'm just waiting for summer to do the work.

[ramble01]

well I found the answer to the overheating problem. Turns out there is a crack in the cylinder head so there is exhaust in the radiator. I wish I new that before I put a new headgasket in, to the tune of 500.00 as well as a new radiator, and two different brands of thermostat. I think it should be covered under warranty. The re-manufactured engine from S and S engines had a 70,000 mile warranty on it(including labor). the gasket blew after 35,000 miles (but I think it ran hot since I installed the engine) still they didn't pay for the new gasket work (they did send me a gasket) because they said that because the engine overheated the problem must have been my cooling system. But it looks like their engine was the cause of the problems. Maybe they'll send send me a new head at least. last week My mechanic backed of the timing from 5 to 2 (maybe that means something to you) and it does run a little cooler but its lost all its pep and is not much fun to drive. I agree that the radiators seem to be pretty chintzy. the one on my 83 was so much larger(at least 1/3 bigger- and thicker as I recall) than all the ones that seem to be available for the tercels now(particularly ones with space for an air-conditioner). the new one I installed was a double core supposedly the largest available and didn't make a speck of difference. Thanks for all the input, I wouldn't have found out the answer without your help. I'll let you know how the warranty fight goes.

[Petros]

have your mechanic put the time back, I would run it at 10 deg BTDC. retarding the timing causes it to run hot, you will damage exhaust valves. I have seen it, I have had it happen. The factory setting at 5 deg BTDC was for emissions and it causes the head to run hot, stock engines can burn exhaust valves running at factory settings. I have seen exhaust valves break off from overheating and embed themselves in the piston, trashing the whole engine. Running at 10 deg BTDC will actually allow it run cooler.

And than I would consider finding another mechanic. He messed you up by not checking the head for cracks and flatness, and now is about to do more damage to your engine by being ignorant of what the timing does.

[ramble01]

well it does sound pretty lame of my mechanic not to check the head out better. to his credit he offered to put the new head in for free. Are you sure the 10 degrees is the best for the ignition timing? I have a weber carb on it if that makes any difference.

[scouttster]

Sounds like you may have a small leak somewhere. I hope you know that these engines ( 3A ) are very sensitive to water loss.. There is a sensor right on the Alum outflow pipe ( right before it hits the hose / top of engine ) and the radiator has to be full to the top for the sensor, to sense it and work properly.. A small leak, drops the water level below the sensor and can throw the whole engine, idle, etc. out of whack.. On mine it did anyway... Keeping it full all the way is the only way.. A little loss of water and you will have problems..

[Petros]

Ten degree before TDC is the best place for this engine, check it at 800 rpm with the distributor vac advance off and plugged. Some engines you can even go a bit more, but if you get pinging, or pre-ignition (crackling noise from the engine on hard acceleration, or up-hills at full throttle), you should back it off a bit. Carb will not make a differance.

The most timing advance you can run without getting the pre-ignition or ping, will give you the best efficiency and power output. Backing off the timing to 5 deg or less will sacrifice economy, makes the exhaust gas a lot hotter, risking exhaust valve damage (or worse).

[dlb]

just reading old threads and found this one to be exceptionally helpful. i love understanding what i'm reading and being able to use the information to help me troubleshoot on my own later on. cheers!