Overheating?

[badassery]

While driving my 84 Tercel (non 4wd) to work the radiator cracked from overheating. I tried repairing the crack with jb weld and replaced the thermostat. While replacing the thermostat I took off the water pump and it looked fine. Thinking it was fixed I attempted driving it again. I checked to see if it was still holding up and the jb weld had cracked. I then replaced the radiator and tried driving it again. After a little ways down the road it was already up past the red. Not wanting to take any chances I pulled over. What is happening? The upperhose feels hot, the lower is really cold. I have the fan always running when the engine is going. There is no smoke and I haven't seen any coolant in the oil. Is there a clog? Where would it be?

[Neu]

Stuck thermostat. Replace it.

[Snax]

Or perhaps a bad head gasket. If it idles without overheating but overheats very rapidly when you accelerate . .

[Petros]

Welcome to the list Badassery,

I have found the head gaskets very vulnerable on these engines to even a little bit of overheating. There is a flaw in the way the factory allows coolant to circulate around the exhaust valves in the head causing a hot spot. Typically the gasket will fail between the 1 and 2 cylinders. This allows you to still drive it usually, but coolant leaks into the one and two cylinder as you drive and is blown out the exhaust as vapor as you drive. I drove mine this way for six months, I just topped it up with water every few days. I am running high compression with a performance cam and had to replace the head gasket every year. If it is bad it will blow enough coolant out to cause overheating in only a few miles. If your radiator is not plugged and your t-state is fully open, it should not over heat if there is coolant in the system. Once you loose enough coolant so it can not keep up with the heat load the temp goes up.

Even if the engine gets hot, but never into the red, you cans still damage the head gasket. If the temp gauge went into the red, almost certainly the gasket is toast.

Not to fear however, there is a fix, and replacing the head gasket is not as bad as it might seem. I can do it under 3 hours (of course I have a lot of practice too). To help cool the head more evenly all you have do to is drill some extra coolant holes in the head gasket right under the exhaust valves (there is a repair guide where I have a picture of where to drill it). It keeps that hot part of the head around the exhaust valves cool and prevents losing the seal on the gasket.

Once you have the head off and cleaned, make sure the head is flat and clean from old gasket, and the top of the block too. Before you install the head with the new gasket, clean all the head bolt holes well with solvent, and clean the head bolts well too. Lubricate the head bolt thread with molly grease and torque it down in the sequence in the service manual. If you do not have a torque wrench buy, borrow or rent one. With the extra coolant holes in the new gasket, it should hold up well.

To save time on removing the head, you do not have to remove the intake and exhaust manifolds (including the carb and all the tubes and EC stuff), you do not even have to remove the distributor, the cam shaft or the rocker arm assembly. You just pull off the timing belt, the alternator, the upper rad hose and heater hose off the back, unbolt the exhaust pipe from the manifold, remove all the vac lines and electrical connectors (3 plugs I think, including the one for the distributor, and the two for the temp sensors by the raditor hose outlet), and than remove the 10 head bolts and pull off the head with all the stuff hanging off of it. Be very careful when you set it down to clean it, you must protect the distributor, the carb and the TVSV valve (I broke this two times when I left it on, they are expensive to replace unless you get one from a wrecking yard).

Get another radiator (I do not think a damage plastic header tank can be repaired), there are aftermarket radiators that have all metal header tanks. The wrecking yard is your cheapest source. And make sure your thermostat is working properly, or just replace anyway (they are cheap). they should be replaced about every two years anyway.

Good luck.

[badassery]

Wow, thank you for all the info and tips on replacing the head gasket. You make it sound do-able. I should get the head gasket set right? Will it be easy to figure out where all these gaskets and things go once i get in there?

[Petros]

I just buy a head gasket alone, not the whole set, it saves a lot of cost. Sometimes you need the head pipe gasket (if it is metal it can be reused if it is not damaged), about $4. If you are going to rebuild the head than you will need the whole set, if you are just replacing the head gasket than just buy the head gasket alone, about $20. I suggest only use the Fel Pro brand or the Toyota factory gasket (from a dealer).

Good luck.

[badassery]

That's good news. I will pick one up tomorrow and tear into it. I saw your drilled gasket and plan on doing that as well. Thanks again