My truck is overheating bad. Could it be a bubble in the system? or something else?

So I just bought this truck and it is absolutely mint other than the windshield needing to be replaced. so I drive it home and it overheats. Call the guy, he said he meant to flush the system and that it was 1005 water in there, so I'm thinking he must not have done something right. I plan on flushing it all and running 50/50.
Has anyone else had an issue with this, because I also noticed that the heat doesn't really come out at all and I'm nervous the thermostat is sticking or something.
Any help is appreciated, thanks.

The lack of heat the the thermostat would be 2 sepereate issues. As it will pull hot coolant from the rear of the motor, before the thermostat.

If you are overheating there are in my history 3 mail culprits

1) Fan is not engaging. This will usually prove itself if you are highway driving and temps stay normal, but at a stop it heats up.

2) Water pump is giving up, this can happen at any moment at any time with no warning. When the engine is cool pop the radiator cap, top off the fluid and have someone else start the truck. The water should start moving. It should pull it down a little, there shouldn't be a current until it heats up but it still should have a noticable motion.

3) Thermostat, the easiest and cheapest part of the equation. It will heat up until critical shutdown. Easy test is to remove the thermostat and bolt the housing back down. Let it run a while, if it never overheats/heats up you found the problem.


These are the 3 main issues with an overheating truck. These arent the only 3 but 98% of the time its these.

It is EXTREMELY possible that there is a bubble in the system, i have had it happen many times, you will look stupid but i wind up having to leave the cap off while its warming up and while hanging from the driver door area jumping up and down and rocking the truck hard untill it burps and i notice it cooling like its supposed to...

Also, after truck is warm, turn it off and feel around the radiator, should be warm\hot all over. If it has cold spots, a good flush "may" fix it, but if it's clogged too bad, will need a new one, or a radiator shop.

jawzs2 said:

Also, after truck is warm, turn it off and feel around the radiator, should be warm\hot all over. If it has cold spots, a good flush "may" fix it, but if it's clogged too bad, will need a new one, or a radiator shop.

Click to expand...

also ran into those symptoms if there is an air bubble in the system, those air bubbles are annoying as hell!

If the truck doesn't have interior heat its one of 4 things (given that having hot coolant isn't an issue). 1. heater hoses kinked/blocked off 2. heater core plugged 3. blend door stuck in cool position 4. busted water pump.

The engine overheating can be caused by a few things.

First thing to check is the head gasket, that will cause overheating very quickly and all that heat will only compound on a bad head gasket. A quick way to check is to remove the radiator cap and start the truck. If the radiator is bubbling and constantly sourcing air, its possibly a head gasket, a compression test will tell for sure.

Second, straight water or air bubbles. Water alone cannot cool as effectively as properly mixed coolant and air has almost no cooling at all. I've seen plenty of engines that will overheat just sitting there when running straight water or with air bubbles but will run just fine when filled with 50/50 coolant and bled completely.

Third, if it hasn't been cleaned recently and has been running water, you can bet there is sediment in the engine. The only way to clean it out is to flush it, or drain it and put radiator flush fluid in then drain it again. If you flush the cooling system, don't flush the heater core, its guaranteed to poke a leak or clean the dirt out of a plugged hole. Just flush the radiator and block.

Fourth, water pump or thermostat. If its the thermostat, hot coolant won't move through the radiator to cool down. The only real way to check is to replace the thermostat as they are so cheap there is no point in testing the system with it removed unless you suspect the water pump. If you suspect the thermostat, just replace it, the cost isn't worth the time.

If you suspect the water pump, remove the thermostat or run the engine until it warms up. Remove the radiator cap and rev the engine, the coolant should suck down into the radiator an inch or two then shoot back up when you let it idle. Block the radiator if you have to in order to get it up to temp. The upper radiator hose and heater hose near the water pump should be hot and about the same temp as each other. If they are, unlock the radiator and feel the bottom radiator hose until it cools down a bit. The lower hose should be much cooler than the upper hose and the temperature should read a bit below 210 on the temp gauge. If the upper hose is not hot but the bypass hose between the block and intake is, the water pump may be bad.

^^^ is all great advice. One other simple item, especially if the previous owner was running 100% water is the radiator filler cap. If the spring is bad you wont maintain pressure and at 212 F you're going to boil over.

Also, if he's been running just water for a while you are going have some internal rust going on and the thing that usually fails is the water pump.

I hope for your sake he wasn't that kind of lazy dope.