garyw59

Looking for answers for a long time. Truck runs great normal driving, but gauge reads heat middle of gauge. When I drive hills heat will rise to overheating and peg gauge. I let off power and it will cool back to middle. I have replaced "everything" almost, so it will be easier to say what I haven't replaced.
Still have origional intake manifold and carb and related attachments. Have replaced engine with stage 2 from 22re performance, all coolant hoses, distributor, starter, alternator, and have now put in my 4th new radiator. 2 were all steal and blew seams, 1 plastic res type, and now a 3 row aluminum.
The truck is totally driveable , it just always runs to hot and will overheat underload on hills. Truck runs great and passes cal smog with flying colors. I'm a decent mechanic and know all the basics tuning. Timing is perfect and distrib is new.
Even on start up the radiator will start seeping coolant from upper radiator hose(never lower one or any other) even as the radiator is still cool. The 2 new steal radiators that failed blew soldered seems just off the side of upper radiator hose area.
I know it sounds odd, but the only things haven't been replaced are the steal tube between the 2 lower rubber hoses, intake manifold and all sensing components, carb and air cleaner assembly, and gauge in my dashboard.
To finish, under my hood 98% of everything has been replaced and the problem continues. Before and after replacing everything the problem hasn't changed.
When I first bought truck radiator had a leak and I had to drive it a 100 miles home. Seller said top off with water and don't tighten rad cap and it would make it. He was right and the gauge stayed below 1/3 although the heater would not even keep the truck warm.
I'm at a loss and have run out of ideas. Radiator just seems to get to preasurized and somehow I have to guess circulation is not up to snuff, but why??? EVERY FRICKIN THING IS NEW
Thanks for any ideas out there.

Gary
Santa Cruz, Ca

old87yota

Welcome to YotaTech!

Have you verified that the engine is actually overheating? It sounds like it is, but the coolant temperature gauge may not be accurate.

Do you have a copy of the Factory Repair Manual? It has test procedures to properly test your coolant temperature sender (sender gauge) and the gauge itself.

Is your current radiator leaking now? If it is, you should fix it.

What thermostat are you using? Have you checked it in a pot of hot water to see if it opens at the right temperature? The thermostat should open at 88°C or 190°F. I have found that Genuine OEM Toyota thermostats to be the best.

What do you mean by the radiator seems to get pressurized? The cooling system should naturally pressurize to about 0.9 Bar (13 psi) as it warms up. The radiator cap should relieve pressure beyond that point. If excessive pressure is building up right from startup, you may have some serious problems with combustion gas entering the cooling system.

Also, just because parts are new, does not necessarily mean they are good. Do not rule out new parts just because they are new.

garyw59

first i'd like to thanks you for your reply: As to yoour questions. !, I agree the in dash gauge may not bbe accurate, but it does show increases and drops in temps as I go up hills or under heavy load. 2, I have the manual, but when I just put in this latest new aluminum radiator I also replaced the sending unit. 3, The new (2 weeks old) aluminum radiator is nnot leaking. What has happened with all 4 radiators is as the engine warms up it will seep from the upper return hose at the point where it is clamped to the upper inlet. Once the thermostat opens and flow starts the leaking tapers off and stops. I'm guessing it stops seeping as the rubber hose warms up and seals better. 4, I just rreplaced the thermostat when I put in the latest radiator. It's a 185. 5, I say it gets preasurized because of the seeping from the hose no matter how tight the clamp. I did replace the hoses but it still seeps. For some reason with all 4 radiators it only seeps from the upper return hose and only where it is clamped to the radiator. New radiator, hose, and clamp. I would think the preasure relief cap would transfer the preasure to the over flow tank instead of leaking from the hose ??? As far as combustion gas I don't know how that might happen. As I said this is the second engine now with this same problem. The only component that's no t been replaced was the intake manifold. I know the coolant returns from engine to radiator thru the intake manifold. Is there something that could go wrong with manifold that would allow this?? Plus yes tthe preasure should be relieved by cap which is a new one again that came with new radiator 4th one now. The 2 steal tanks blew leaks thru the seems solder point near the return port both times. The plastic mishimoto did not fail but was only a 2 row and allowed it to over heat quicker so got the new 3 row alum model. The 2 steal ones that did start leaking were both fairly cheap. 1 was a 2 row and 1 a 3 row. The 3 row did ok till it started leaking thru solder joint.
Everything has been replaced at least once except intake manifold and aircleaner assembly. I just don't know how these could make a difference.

Gary
Santa Cruz, Ca