1990 Nissan Pickup - Overheating/No Heat

[Britches]

Originally Posted by junior3382

Then there is a blockage. They should warm up. and if there is a blockage, then there is your overheating problem too. A flush may not remedy this, you may have to pull all the hoses off and pray it is in one of those, and not in the motor

If there's a blockage, why wouldn't the engine overheat when the thermostat is out?

What's the best way to flush the system?

Also, what exactly do you mean when you say a blockage in the motor? Where would it be in the motor and how would I clean it?

[junior3382]

My suggestion is take it to a radiator shop and have them pressure flush the whole ssytem. Now it is weird that removing the thremostat aloows it to run cool, but could insdicate where it is being blocked. Perhaps it is the thermostat itself that is faulty, or maybe just installed wrong. If it is not openeing when it is supposed to, there is both issues. Now what I meant by a blockage IN the motor is this. The collant runs all through out the block. its purpose is to draw the heat away from your cylinders and cool it. those ports through out the block are much smaller then the hoses on the outside of the motor. So if there was sludge or a blockage INSIDE the block, then it will be a lot more difficult to clean it out with out tearing into it.

Here is my ultimate suggestion. Take it to a radiator shop, you could even try a lube shop like jiffy lube and such, and have them flush the system. Then, check the thermostat itself, double check it is the right one, and that it is functioning properly. if the flush comes out clean, and free flowing, and the thermostat is fine, then you have a mystery that we may need more symptoms for. Granted the heat problem could still be the core, but I would check the other things first. Heater cores are expensive and a pain to replace.

Does this make sense? Give it a shot and let me know either way.

[Britches]

Originally Posted by junior3382

My suggestion is take it to a radiator shop and have them pressure flush the whole ssytem. Now it is weird that removing the thremostat aloows it to run cool, but could insdicate where it is being blocked. Perhaps it is the thermostat itself that is faulty, or maybe just installed wrong. If it is not openeing when it is supposed to, there is both issues. Now what I meant by a blockage IN the motor is this. The collant runs all through out the block. its purpose is to draw the heat away from your cylinders and cool it. those ports through out the block are much smaller then the hoses on the outside of the motor. So if there was sludge or a blockage INSIDE the block, then it will be a lot more difficult to clean it out with out tearing into it.

Here is my ultimate suggestion. Take it to a radiator shop, you could even try a lube shop like jiffy lube and such, and have them flush the system. Then, check the thermostat itself, double check it is the right one, and that it is functioning properly. if the flush comes out clean, and free flowing, and the thermostat is fine, then you have a mystery that we may need more symptoms for. Granted the heat problem could still be the core, but I would check the other things first. Heater cores are expensive and a pain to replace.

Does this make sense? Give it a shot and let me know either way.

Yes, it makes sense - thanks for your advice!

I talked with someone today and they thought (like crabtruck did earlier) it almost certainly was air in the system. I initially wrote this off because I've had two people bleed the system, but I learned today that Nissans can take two or three hours to bleed and neither of those bled it for more than a few minutes. The thermostat has been checked and it's good. I'm thinking I'm going to have the system pressure flushed then have the system bled once it's refilled.

[junior3382]

That is a great idea, once done, let us know how it turned out. I hope I helped, and I wish you luck bud.

[Britches]

Originally Posted by junior3382

That is a great idea, once done, let us know how it turned out. I hope I helped, and I wish you luck bud.

junior3382,

Thank you so much for your help and advice! The problem has been fixed! He flushed the system, installed the thermostat, and bled the system. Now the heat works and the system doesn't overheat. Thanks again junior3382!

Also, thanks to crabtruck for your help and advice!

[crabtruck]

Junior gets his teeth in a problem, either he comes up with an answer or he's coming to your house LOL. Glad you're good to go.

[shadow]

i would takeone line aloose at the motor plug the line remove radiator cap and aply air presure into the motor that will tell you if there is a blockage repete on other line iwould also inspect my hoses you could have a bad hose that is colapsing or kinked somewere