91 240sx Over Heating Solution I used to fix the prob

[spikey144]

91 240sx auto (This is what I wrote before to see if anyone had any ideas)

Changed Thermostat, Water Pump, Rad. Upper Rad hose is hot, lower is cold. I bled the system many times as well with the front of the car jacked up. Some ppl say head gasket but i don't think its the case here. Compression test read all same with all cylinders. I think its a flow prob but whats the best way to check my prob??? Take out the thermostat and see if i still overheats? Its a new water pump not a re-man, so i'm sure the impellers are installed correctly. Any info would be Great, thanx

Tips: When changing Rad, always change Rad cap
When changing Water pump, change Thermostat

Here are the steps to take if you like to see what I did:
1. Check your coolant Level
Level was fine but a little dirty so I flushed it out. At this time check your heater core by passing water through it and making sure it comes out the other end (do not blast the water as your heater core can't take that much pressure).
2. Feel all hoses (Are they hot/cold)
For me upper hose was hot, Lower was cold
3. When does it overheat? ( While driving, Idle... ect)
Overheated after driving on the highway coming to a stop. If it overheats on the highway its most likely your water pump (not the case for me) If you replace your water pump and it still overheats while driving (not idle) check to see if the impellers are pointed the right way. Sometimes on re manufactured pumps, the impellers(little fan blades on pump) are installed backwards causing no flow.
4. Clutch fan. Not usually the case but would cause overheating.
5. Is your Rad plugged?
Put your hand behind the fan(watch out you don't burn your hand on the engine or get caught by the fan), do u feel hot or cold air? For me it was cold so no coolant wasn't going to the rad to cool down. You can also touch the rad to feel the temp.
6. Is your thermostat opening?
This was my Problem!!!!! If your lower hose is cold (upper being hot) while your car is operating at normal temp, your thermostat isn't opening (so no flow to Rad). Make sure that little pin is facing up so that air bubbles can flow out (coils facing the engine block)As of right now i'm running without the thermostat (it takes awhile for your car to warm up) and no problems. I put in a new Nissan thermostat and it did overheat ONLY BECAUSE MY RAD CAP WAS BAD. It was holding 3 psi when it should be 13psi.
7. Any air in the system? Did you bleed it properly (there a ten mil nut above the thermostat) You can also jack the front up so your rad is same height as your engine as you are bleeding.
8. Try a compression test to see if all cylinders are reading the same. Mine read all same.
9. Your worse problem( In my opinion) Head gasket.
You can use an gas analyzer to see if coolant is burning in your engine. Is there white smoke from the tail pipe? (If so coolant is leaking inside your engine)This is common for the 240sx but don't jump right away to conclusions(follow the above steps).
10. Check your timing. If its out by a single notch it can overheat.
I hope I've been of some help here.

[RED_DET]

I have seen this issue before and no matter what we did, it still over heated. The owner finally ended up putting in a SR. The problem is more than likely the head-gasket as it shouldn't take that much effort to the bleed the system.