Bought the car, it wouldnt heat up, went to replace the thermostat and there wasnt one. Put the thermostat in and found that it overheated, its boiling into the coolant tank after running

. Tryed numerous ways to get it to bleed and it seemed like it would bleed but then itd just start running hot and boil off a good amount of coolant. Thought there was a more serious problem, turned out there was in a way. Did a pressure test on the cooling system but no leaks. Did a compression test, all 4 cyls hold 170psi roughly except 4 which is at like 90. The piston looks the same as the others when viewing it with a borescope.

So I pulled the head and found that the #4 was pushing out into the water passages. Sent the head off to the machine shop, it pressure checks fine, I have it milled to correct warpage and new valve seals installed. Str8 edged the block and its fine, maybe .001mm warpage at one point. I put the exhaust back on and only put on my header and downpipe for right now.

Crank it, fill it with coolant, and it still does the same thing, so Ive fixed one problem but I still have another with this cooling system. I took the water pump off and flushed water thru the motor by holding a water hose to it, takes a little bit but it comes out the top coolant port to the radiator and thru the heater core outlet. Ran it thru the heater core and it comes right back out the other hose, ran it thru the heater core inlet back to the motor and it flushes out the front where the water pump mounts like it should.

The car has a new water pump on it so says the previous owner and it looks new, its a asc water pump, no play in it, I dont see a leak from the weep hole underneath. Also I put a new nismo thermostat in the car, checked it before install and it is opening up at 150degrees like it should.

It just seems like the car doesnt want to flow coolant at all once it heats up.

Sorry for the long read but I just wanted to make sure I showed all the bases Ive run with this damn thing.

 

BTW the car is a 1995 with a KA24DE

 

I ran into the same problem these engines are a pain in the ass to get the air pockets out of the engine. what i did is get the motor up to running temp with out any coolant in it as soon as you do shut it off and fill it back up and put the cap back on and let it run. for a while. keep your on the temp. if it doesnt over heat shut it off and let it sit and cool down and then check th ecoolant level. you should be good to go.

 

so I came to find that the aftermarket waterpump that I had was bad, It was somehow getting air in thru the weepholes in the top and bottom and aerating the cooling system as I was trying to bleed. Swapped to a OEM nissan pump and bleed the car for 30mins and the damned thing finally bleed and stopped overheating.

 

The main reasons for overheating are coolant level is low, leak in the engine cooling system, thermostat is bad, water pump is failing, radiator cooling fan is not working, blown head gasket. so now you must have to take your car to an expert. you should visit to a good auto repair shop. I suggest you a best auto repair shop i.e. Transmission Experts, they are really helpful. Transmission Experts also offers a wide range of auto repair services including Transmission rebuilding, Radiators, Drive shaft repair, Breaks, shocks, alignment, suspension etc.