86Shredder

I have an 86 Toyota Pickup 4x4. I start the engine and drive for a bit, and the temp gauge will continuously climb into the hot zone. When it gets hot, if I turn the 22r off and then start it again about 5 seconds later, the temp gauge goes back down into the normal range. What is causing this? I changed the thermostat, but it didn't help. It only seems to overheat on the first start up. After it gets hot and I turn it off and restart it, she will be in normal temp range and drive fine.

blake.nemitz

wrong temp range thermostat, it is not uncommon to have a bad brand new one. also check your cap you need to hold all the pressure too

86Shredder

Which thermostat do you suggest? What do you mean check the cap? Another issue is that I seem to have a slow leak with my coolant. My reservoir will dry up, but my radiator stays topped off. I don't even bother filling the reservoir.

James Woods

iTrader: (1)

You should get an OEM t-stat, they are not that much more and you will have the assurance that it is correct. The cap is there to put pressure on the cooling system, a cooling system under pressure will boil at a much higher temp than one that is not under pressure or enough pressure. I would suggest getting a pressure tester and checking your whole system. Also did you make sure to burp all the air out of the system when you changed the t-stat?

86Shredder

No, I did not burp the air out after changing the T stat. How do I do that? How do I determine if my cap is good? What about the slow loss of antifreeze?

86Shredder

Now that I'm really thinking about this cooling issue I can recall that sometimes I notice the main radiator hose leading to the TSTAT sometimes is sucked in. Like an unequal pressure is occurring. The hose will literally be smushed like a vacuum is sucking it in.

James Woods

iTrader: (1)

To burp the system, you fill the radiator up and leave the cap off, start the truck and run it for a while until the radiator burps a bubble and the coolant level drops, you will know that it is complete because both radiator hoses will be hot. Fill the radiator back up and put the cap back on and fill up the overflow. When you have an air bubble in the cooling system it will cause it to get hot because air heats up quicker than water, it will cause other things like gurgling in the heater core.

86Shredder

Ok just went out and started the truck. Checked the cap seal looks ok. The truck spiked in temp then went down. Both radiator hoses were warm (top and bottom). So the radiator has flow. No oil is in the coolant. No coolant in the oil. Head gasket seems fine. So I'm thinking thermostat?

What would cause the thermostat to stay shut/stay open?

I think that is what is happening? Will an OEM thermostat fix this?

James Woods

iTrader: (1)

If both radiator hoses are getting warm than it may not be the t-stat, if it were staying shut one hose would be hot and the other cold, if the t-stat was sticking open then you would most likely never get up to operating temp. Just because there is no oil in coolant and vise versa doesn't rule out a head gasket, they can pump exhaust gas into the cooling system, pushing out coolant and basically filling it with air. You can also check to make sure the radiator is not restricted, a quick way to do this is when the truck is running and the fan is drawing in air, put a piece of paper up against the front of the radiator and see if it gets sucked in.

86Shredder

Ok, let me try to rephrase. I started the truck the top hose began to warm and the bottom was cold. This was when the temp kept climbing (TStat shut) then the temp went down and the bottom hose was warm (Tstat open flow through the system). So I think its just the Tstat being finicky. How could I check more into the headgasket? The truck seems to run fine and seems to have power. The exhaust does not smell sweet. No bubbles in the radiator when the truck is running. I'm going to check the radiator right now with paper.

James Woods

iTrader: (1)

If the temp keeps climbing and the t-stat is not opening then yes that would be your problem, the t-stat works by way of little wax pellets inside heating up and melting at a specific temp and getting solid at another temp. Checking the head gasket can be done by a tester from an auto parts store that checks for hydrocarbons by changing the color of the chemical inside this glass tube (I never liked this way) or with a machine that most mechanics shops have, I have tested it by smelling the overflow for hydrocarbons, you have to know what you are smelling for, or fill up the overflow and run the truck while watching the fluid in the overflow and once it gets to the point that the t-stat opens you can see a lot of tiny bubbles in the overflow.