midtown5dw

Basicaly the title says it all. I just spent 2 weeks swapping this engine and now this happens. There arent any leaks that i can see. What are some common reasons for this? i need my truck back!

904_runner

Did you replace your thermostat?

Innervision

did you make sure and remove all the air from the coolant lines? Run the truck with the radiator cap off and heat on high then keep filling with coolant till the level does not drop.

midtown5dw

no i havent where is it?

mt_goat

Bad fan clutch, clogged radiator, bad or backwards head gasket, trapped air pockets in cooling system, t-stat stuck closed (pretty rare with Toyota t-stats)

abecedarian

water pump, collapsed radiator hose, possibly incorrect ignition timing

bigarms23

also replace all the heater hoses change the thermostat and make sure you have the right radiator cap

OutlawMike

First, just make sure you have it full of fluid. Like is stated above, start the motor, heater on high, and fill until the level comes up the filler neck of the radiator.

One thing that caught me on my 3.0 after my rebuild is that you can fill the radiator to just below the neck, it looks full, but the top radiator hose comes in just at that level. I stopped filling mine when I saw it below the neck and started it up. The temp came up, and started to go way up when I shut it down. Scratched my head, looked in the radiator, looked fine, added more fluid, and it kept going in, for a long time without changing the level in the radiator. The upper radiator hose neck is just at that level and tricked me into thinking the block was full already.

Once you know you have all of the fluid in there that it will take, the next culprit would be the T-stat. Unfortunately, you will have to drain the radiator down to replace the T-stat. Get a factory T-stat, do not get aftermarket.

It could be your pump, they they usually make a lot of racket when they go out. For the pump to stop pumping the shaft has to seize, which makes a lot of noise with the timing belt, or the impeller has to come off the end of it. Usually the bearings and seals start to go and it still pumps but makes noise and leaks fluid at the shaft seal. Use an automotive stethoscope to listen to the pump, see if it is making odd metal on metal noises.

Cheap aftermarket upper/lower hoses might collapse on you and not flow enough fluid. You can see that, just look at them when it is running (but don't let the motor overheat) see if they are sucked down.

Ignition timing that is too far advanced will cause overheating and can melt spark plugs. (This was noted above.) Make sure it is timed as per the FSM. It is not as simple as connecting a timing light to #1 and turning the distributor. You need to get the computer in the right mode. (eliminate the advance circuit)

Some more info would help. Make/model/year of vehicle is always good info.

Does it overheat at idle? Does it overheat only when driven in traffic? Does it run hot on the freeway? Or can you drive it at all?

What is the history of the motor? Was it a donor motor from another vehicle? Or was it a rebuild? If it was a donor, did you witness it running fine before it was pulled?

Good luck,

Mike

abecedarian

to add- radiator hoses don't always visibly collapse when they fail- the hoses are two layers of rubber with something in the middle (nylon string from what I can tell) and if the inner layer separates from the outer layer then collapses it will cut off coolant flow. Though this is more likely on the suction / draw side, it can happen on the pressure side if the inner casing actually cracks and the pressure forces the inner lining to be blown closed. One reason why many 'suction' side hoses on many vehicles have a metal spring inside to prevent the hose from collapsing.

OutlawMike

Ahh, good info, I was not aware of the double layer in the design. I bought a cheap lower radiator hose for my old Chevy pickup once. It did not have the spring in it and it collapsed right away, the whole thing sucked down like a straw in a really thick milkshake.

Thanks for pointing that out,

Mike