Hello, just looking for a little advice on where to go next. My toyota has over heated three times all going up passes in colorado. each time the coolant boils over. The last time it over heated the the heater stopped blowing hot air. The t-stat was replaced and it did not fix the problem. I just bought the truck. It was sitting for 2 years. The truck has 178,000 miles but was rebuilt at 100,000 miles. I was told there was a radiator leak. I was also told they put stop leak in the radiator. I also blew a radiator hose one cold morning after starting. I pulled off the oil cap and yes there is very small milky drops of oil. Very little tho. I changed the oil and it looks almost brand new so I figured a little condensation. Could this be water pump? Head gasket? any Ideas Thanx
HARLEY

 

If you replaced the thermostat and its still over heating, then it sounds like the radiator is bad.

 

x2 on the raidator. espically if they put leak stop in it. all that stuff does is clog other parts. i would get a bottle of raidator flush and flush your system out. that mught alos allow you to find the leak in the raidator. and decide if it needs replacing.

 

Under a 100 bucks for a new radiator. I change all of mine with new hoses every 5 years anyhow, and install failsafe thermostats. Heat x 22r = blown headgasket.

 

Is the fan shroud installed?
I'd vote towards the radiator too, but I wouldn't rule out the fan clutch either. On level ground you should have enough forward velocity to keep good air flow over the radiator but climbing hills will put a load on the engine and cause it to heat up and if, as you slow down going up the hills the fan is not able to keep air flow going... well you get the idea. But we're talking Colorado in the winter so it's probably cold enough outside so...
Having said that... given that they put the leak crap in the system, radiator is the most likely problem.

As for the heater stopping when it overheated- vapor in the cooling system gets into the heater core and heat stops.

 

Try taking your radiator to a radiator shop and have them flush it with high pressure from top to bottom and bottom to top. I had used a flush kit and additives on mine and thought it was clean. You should of seen the rust come out when high pressure got to it. The shop I use, you have to take it out of the truck and to him to flush and fix and it was about $35 to seal a hole and braze one of the mounting brackets back on. Also make sure your thermostat is good. If in doubt change it, it is not much any ways. With it cold you can start your truck with radiator cap off and when it warms up you should see water move which will give you an idea if your water pump and thermostat working. While you are that far, I suggest just taking a water hose to your heater core and flushing both ways, it can push junk out and help with heating inside of cab. Hope this helps.

 

That does'nt get everything out, especially since stop leak invaded the system.
Slap another one in, I just installed another one on my 87 2wd for 86.00.
While your at it, pull the hoses' off your heater core and shove your garden hose sprayer in the inlet pipe. It will make a mess all over the engine, but knowing you washed out what you could outweighs the mess.
Replace your thermostat, and if you dont know how long the fan clutch has been on the vehicle, then change it also.
Remember" you'll more than likely get a pocket of air in the water pump at start up, so it will try to overheat the first time.
Just kill it, and let it sit for a few moments, and you should be good to go".