94 Overheating

[XJMUDDER]

Yes its boiling out the of the radiator my son said that it was building a lot of back pressure , after about 10 mins of running it it went straight to the red line on the temp gauge and started boiling out of the radiator it was even trying to come out of the seems of the radiator tank ! i don't really think its the water pump i have been told it would make noise and i would know it ? plus it seemed to be flowing through the radiator so that would make me think the pump is working , i don't see any signs of coolent on the dipstick or running out of the block anywheres , my son works on a lot of subarus and said that the way this toyota is acting is just like a bad head gasket on a subaru thats why i keep thinking or saying its the head gasket but to me with no signs of it in the oil makes me think its something else , i don't think we put the t-stat in backwards but with my luck i could have ! i was also told that i should run a oem t-stat ( which i didn't) but was wondering what you guys thought if i tryed it with out a t-stat in it ? without one in it if there was something else wrong it would still boil over right ? also after we ran it for 10 mins it still didn't push out any heat . Thanks for the help and keep it coming !

[bradrhale]

you wont always here a water pump when failing. if it is bubbling as bad as you claim, than you do have a problem and a serious one at that. before diagnosing this as a head gasket problem, do a compression test. let hold for a few minutes on each cylinder and see if any one cylinder pressure drops rapidly. remove all the plugs and turn the crank by hand to keep pressure in each cylinder that you are testing.

[hotrodpc]

SO is this happening instantly, like on a cold motor, or is this boiling over after is has overheated. Normal for overheating to boil over. I mean when motor is cold. You first start it up, then it will immediatly start bubbling, then you have a cracked head, not a blown head gasket. As Brad suggested, do a compresson test, but do not be suprised if compression is good too. The head crack can be in the exhaust port behind the valve, which is past the combustion chamber, therefore compression test could still show good. Let it get cold, like from sitting overnight. Take the radiator cap off, and start it up. IF it immediatly starts bubbling, start looking for a head.

[hotrodpc]

Oh, and don't think what you been told is correct either about the water pump being bad. I am leaning more toward waterpump now too, that I reread your post and you say it takes 10 minutes to overheat, and you say you can see water flowing thru the radiator. Water will flow thru the water pump just by overheating as the water heats, it expands and it will move. You will NOT always know a water pump has gone bad. They can out differant ways. Many times the shaft bearing will go bad and that, yes you will know. Or the bearing race in the pump will rust through, and it will leak coolant out a pressure hole around the bearing race. Not sure all water pumps have that, but most I have seen do. That is another way they can go bad. Those 2 ways you will KNOW yes the water pump has gone bad. If the pump impeller has broke off the shaft, the bearing could still be good and you would NOT that until you took the pump off. Also the impeller could be seized and the shaft is spinning inside the impeller. Just don't rule it out as of yet, and go getting expensive. First do the compression test and see what the results are. Next would be to remove the water pump and hope for it to be bad. If its good, well, not loss, it had to come off to change the head anyway.

[XJMUDDER]

Originally Posted by hotrodpc

SO is this happening instantly, like on a cold motor, or is this boiling over after is has overheated. Normal for overheating to boil over. I mean when motor is cold. You first start it up, then it will immediatly start bubbling, then you have a cracked head, not a blown head gasket. As Brad suggested, do a compresson test, but do not be suprised if compression is good too. The head crack can be in the exhaust port behind the valve, which is past the combustion chamber, therefore compression test could still show good. Let it get cold, like from sitting overnight. Take the radiator cap off, and start it up. IF it immediatly starts bubbling, start looking for a head.

At the time that we did this the truck had sat for almost a week so it was a very cold motor we never started it until we had the radiator and everthing put in then we started it let it run a few mins then moved it back a few feet then moved it ahead of where it was sitting , we watched and added antfreeze as it need it after maybe 3 or 4 mins it started to bubble from air in the system we add some more antifreeze and it seemed good to go after a couple of more mins so we put the cap on the radiator after about 10 mins the temp. gauge hit the redline ( i was watching it slowly move up ) so we shut it down you could hear it boiling and started coming out a little around the cap and like i said around the sides of the radiator just a little , it to me seems like it got very hot in a few mins that it ran like i said about 10mins . i'll ask my son if he can do a compresson test on it for me but like you said and i have heard in the past its not 100% sure thing. it doesn't seem to smoke either which i have been asked about to just not sure what to do first now.

[hotrodpc]

Here is my thinking on it. If you are certain you are keeping the truck and its worth the repair of a head and head gasket to you. I would get a new water pump. Try it. If it fixes the problem, then great. If not, then you pull the head, and have it checked. I would not replace just the gasket, because I have a feeling, if the water pump is NOT the issue, I am more to believe a cracked head than head gasket. I would say straight up, if its taking 10 minutes, it not a cracked head. But, when you have a crack in a head, even with a cool motor, the crack is not very profound. It will widen as the motor heats up. Then again, the part that makes me think it is NOT a cracked head, if it is building up that much pressure in the cooling system, you'd think that pressure would over power the exhaust gases going out the tailpipe, since it should take path of least resistance, therefore, I'd think you will have steam or smoke out the tailpipe. So I am back to thinking the simple matter. It can still be a water pump. All you will be out is the cost of the water pump and some labor if its the head or gasket, and nothing wrong with knowing the water pump and thermostat are new after having a head reworked and a new headgasket.

[XJMUDDER]

Originally Posted by hotrodpc

Here is my thinking on it. If you are certain you are keeping the truck and its worth the repair of a head and head gasket to you. I would get a new water pump. Try it. If it fixes the problem, then great. If not, then you pull the head, and have it checked. I would not replace just the gasket, because I have a feeling, if the water pump is NOT the issue, I am more to believe a cracked head than head gasket. I would say straight up, if its taking 10 minutes, it not a cracked head. But, when you have a crack in a head, even with a cool motor, the crack is not very profound. It will widen as the motor heats up. Then again, the part that makes me think it is NOT a cracked head, if it is building up that much pressure in the cooling system, you'd think that pressure would over power the exhaust gases going out the tailpipe, since it should take path of least resistance, therefore, I'd think you will have steam or smoke out the tailpipe. So I am back to thinking the simple matter. It can still be a water pump. All you will be out is the cost of the water pump and some labor if its the head or gasket, and nothing wrong with knowing the water pump and thermostat are new after having a head reworked and a new headgasket.

rigs are a pain in the a** ! but love to play with them ! what brand of water pump would you get ? some say everything needs to be oem and others have no problem with aftermarket stuff , if it was a crack etc. like you said it should smoke alot right ? to me and my son it looks normal after it runs a few you don't see really anything theres no big amount or any big stink etc. . do you know of any good parts places on line ? i have got alot of stuff from rockauto but if you say i should stick with oem parts then do you know of any good on line places . thanks again, all this help is great !

[Crmzendrgone]

If you can another way to tell if you have a head gasket gone bad smell the exhaust itself it it smells sweet then you know it has a leak. I know there is many ways to tell if it has a head gasket leak. Barrow/Buy a pressure tester put in on the radiator DO NOT PUMP IT UP. Start the engine let it run and see if it gains pressure fast if it does then you have a head gasket leak like hotrod said where exhaust gas is getting into the cooling system. The other is a block tester. I think any parts store should caring them it is a liquid form of a sneefer like Hotrod mentioned. It has a tube with a rubber end on it to seal it to the the rad. you pour in the chemical to the fill line(test should be done when engine is at operating temp) and if there is any exhaust gas in the cooling system then it will change from blue to yellow.

Did you figure out if your fans are working I think Brad mentioned to check your fans but I didn't see if you checked them.

Another way to tell if the water pump is bad if possible turn the heat on in you truck and check the temp of the air coming off of it. If it is say 20 degrees cooler than were the engines temp operates at then your water pump can not flow enough coolant pass the heater core, thus bad pump.

I agree with Hotrod about not hearing the pump go bad. I had a town and country come in with a leaking water pump replaced it with a factory pump came back 2days later with it overheating. Found now leaks looked everywhere else with the cooling system cause the pump was just put in new. finally pulled the pump and the impeller grenaded so there was no flow. Hope this helps

[hotrodpc]

As far as pumps go, I have never had a problem with a reman pump. I'd think the only differance in a reman or OEM, is that the OEM may last longer. For this project and purpose that you may be buying a water pump that may not be the problem, I'd probably get one of the cheaper lifetime remans at an Auto Zone or some discount auto part store near you. I am past the idea of it being a blown head gasket. I am thinking if its not the water pump, its a cracked head, which is a bit harder to diagnose becaue like I said, if its cracked in the exhaust port behind a closed valve, your compression test, block pressure test and all cylinder tests will come back good. I am reffering to a crack behind the valve on the exhaust manifold side of the head past the compustion chamber. But, still if that were the case, you'd think you'd get steam or something out the tailpipe. I still lean more toward water pump.

[XJMUDDER]

Originally Posted by hotrodpc

As far as pumps go, I have never had a problem with a reman pump. I'd think the only differance in a reman or OEM, is that the OEM may last longer. For this project and purpose that you may be buying a water pump that may not be the problem, I'd probably get one of the cheaper lifetime remans at an Auto Zone or some discount auto part store near you. I am past the idea of it being a blown head gasket. I am thinking if its not the water pump, its a cracked head, which is a bit harder to diagnose becaue like I said, if its cracked in the exhaust port behind a closed valve, your compression test, block pressure test and all cylinder tests will come back good. I am reffering to a crack behind the valve on the exhaust manifold side of the head past the compustion chamber. But, still if that were the case, you'd think you'd get steam or something out the tailpipe. I still lean more toward water pump.

all man your driving me nuts ! ok so your maybe leaning more to a cracked head ? if that is the case ( oh god ) how much is that going to kill me ? i'm sure it can't really be fixed any clue what a good used one would cost ?or rebuilt one ? now i really don't know what to do !