Questions and Answers
Overheating Nissan
Q. Hi Vince, I am back again for the next car problem: 1990 Nissan pick up truck, 4 cylinder, engine KA24E, fuel injection MPI, no A/C or power steering, 5 speeds.
After replacing the engine head gasket, intake gasket, exhaust gasket, thermostat, radiator, coolant fluid. Car experienced over heated after 20 minutes of driving. I inspected the car condition and noticed the following:
- The heater is not blow hot air like it used to be.
- The temperature gauge needle is at 1/2 way and getting close to the hot zone.
- The radiator is cold.
- The radiator upper hose is warm but not hot.
- The radiator lower hose is hot.
The water pump is not leak or make noise and the vane is about 20 percent worn. Please help.
Thanks
A. Having done a couple of hundred head gaskets on that engine, I'm not surprised that it overheated on you like that. In fact, I would have been surprised if it didn't.
What happened is that the cooling system got air bound. In other words there is a big air bubble in the system that has to bleed out. After a job like this the heater core drains out and the cylinder head is empty. Just filling it with coolant will not get it back into those areas. There is no dedicated bleeder screw for the cooling system in that engine, so this is the procedure I use to bleed it.
Fill the cooling system full of coolant. Then put the radiator cap on and fill the coolant reserve tank about 4/5 full. Put the heater temp selector in the full hot position. Start the engine and let it run. Look in the coolant reserve tank and you will see air bubbles coming up as the engine warms up. After about 10 or 15 minutes (or if it begins to boil over) shut the engine off and let it cool down. The engine will draw coolant in from the tank. Fill the reserve tank and do it again. This will purge most of the air out. The rest will purge as you drive.
Now I know some guys will say to remove the heater hose going into the heater core, but the tubes on the core get brittle and the hoses get stuck hard on them. Taking the hose off at that point makes it possible to break it. A risk I'd rather not take if I can help it. But that's just me.
