93 6-cys 4x2 auto 4runner

The truck overheated, but just before that the temperature gauge fluctuated from normal to just before the red, changed thermostat and coolant, drove for 50 miles freeway - temp was normal, by the time I exited the freeway, it started overheating again. Allowed to cool off and topped off radiator with about quart of distilled water.

I started it again to burp it and there was some loud clicking sound coming from the front area of the truck - and the sound went away after a few minutes - maybe water pump going bad.

Next morning I can't even start the engine. When I crank it, there was just 1 thud. Can a bad water pump freeze up?

Please help.

Possible blown HG. Sitting overnight allowed the cylinder to fill with coolant and hydro-locked the engine. Pull the sparkplugs (all of them) and try to turn it over.

The water pump or the rad could be bad which caused the overheating issue, but the water pump would not have had anything to do with a thud upon trying too start the engine. The water pump impellar doesn't have anything it can hit, and if it did it is unlikely you would here it. Even if it froze, it is belt driven an d you should have heard the belt sqeel on teh stuck water pump pulley. I imagine if the t-belt broke it could have caused a thud, but if it was a loud thud, I would agree with OOP's that you probably hydro-locked it.

Yep. 6th cylinder had coolant in it - also the throttle body. I removed all the spark plugs as suggested and it spit out the coolant from that cylinder.

I guess need to replace the head gasket and water pump -hoping that it did not damage the bearings.

Any other suggestions?

... and thanks for the input - it's greatly appreciated

Also plan on replacing the knock sensor wire and knock sensor, the knock sensor wire gets brittle and any movement of it damages the wire. Dealer techs couldn't confirm that the knock sensor itself goes bad, but due to where it is located it is worth changing it as well. You will also want to buy new head bolts, studs, or non TTY(torque-to yeild) headbolts, do not reuse the ones in it, and insist on this if you have a shop other than the dealer do the work.

I would also send out the injectors to be cleaned/rebuilt, and have the heads checked.

Providing you don't find any damage other than the HG and a valve or 2, it should run you about $1k to do the work yourself, or if you have more $$ than time or figure about $2k at a shop

If you do this yourself,

And you do replace the knock sensor, which is under the intake manifold, hard place to get to later....

The torque spec is 51 in-lbs for the knock sensor. Took me a while to find that number, got it from a Toyota Tech, it is not in the factory manual.

I did my truck back in January, due to a dropped valve seat. Check some of my other posts for more info on pulling the heads on this motor.

Good luck,

Mike