I have a 92 V6 (3VZ-E) engine pickup truck that I recently replaced the timing belt, water pump and thermostat. After starting it up the water temperature shoots up into the red after driving around the block. Anyone have any ideas? I searched the archives, but, didn't see anything that addressed my specific problem. It ran fine before the timing belt / water pump / thermostat change.

Some of the particulars:
- When I replaced the water pump the dealer gave me a 16100-69485-82 water pump which I later found out was for a 93 and later truck. The only things I noticed different than the one I took off were it had a gasket included instead of using RTV sealant and the pin for the timing belt tensioner was missing. I assumed the missing pin was a manufacturing error and just pressed the pin out of the old pump and installed it in the new one. Talked to the dealer over the phone and when the guy compared pumps he saw the same thing I did. Seems to make sense since I think the 93+ trucks use a hydraulic tensioner.
- After the truck began to run hot, I pulled the thermostat and checked it in hot water. It appeared to behave the same as the one I removed so nothing was obvious.
- The upper radiator hose gets too hot to hold, while the lower one is basically at room temp. I was expecting the lower hose to be at least warm to the touch. Based on that I was assuming the thermostat was probably bad and not allowing water to flow through the radiator. Since the thermostat seems to check good though I'm not sure that's right.
- The coolant level in the radiator looks good, although, I didn't do any special bleeding tricks besides running it with the cap off and topping it off.

After the timing belt change the truck fired right up so I don't think I have a timing issue or any thing like that - it has the same power , no strange noises, etc. Anyone have any advice? I'm suspecting maybe there are more differences in the water pump than I saw, but, hate to tear everything apart on a hunch.

Thanks for your help!

 

burp it. You have air trapped in there.

 

I second with deathcougar on this one.

 

If it's not an air bubble: I had the same symptoms on a 1990 celica 2 weeks ago. I could not find anything, checkes thermostat in water etc. etc.
Turned out that the prop on the waterpump was loose!! It's crimped/stamped on and it somehow loosened. So there was actually no coolant flow resulting in a hot upper hose and cold lower hose. Since the temp sensor is attached on the head it spiked hot within a few minutes.

 

Thanks everyone! Turned out to be a giant air pocket. Parked on an incline and let it run for a while. Didn't burp while running, but, after shutting it down and topping of the coolant it let out a couple of giant belches. All is well again.

Thanks!