Overheating...

[TwoForties]

Hey guys, my 91 240sx ka24de has been overheating and I need to find out why. It usually overheats after like 5-10 minutes of normal driving. So far I have taken out and tested the thermostat, it opens when it's supposed to(Yes I replaced the gasket). I flushed the system until clear water came out(took five times). I also replaced the radiator cap with a 13psi one. I filled the coolant to the top, then bled the system(maybe improperly?). Okay, so after all of that I drove the car on and off the highway for 30 mins and it didn't overheat. The next morning, I checked the coolant and it was still full. But on the way to work it began to overheat again(it took a little longer than before, but it still did). When I got home, I tried bleeding the system again. After finishing, I drove it for almost an hour, cruising and beating it yet it didn't overheat. When I bleed the system I ,1.) turn on the car. 2.) take off the rad cap and take out the bleeder screw. 3.) I fill the radiator with coolant until coolant squirts from the bleeder valve hole. 4.) then I screw in the bleeder screw and close everything up. Am I doing something wrong here?

[Sileighty_85]

Check your clutch fan to make sure it has some resistance when you spin it. Fan might not be spinning fast enough.

radiator is obstructed.

Water pump fins might have rusted away (seen that happen on some iron bocks)

[laurentj23]

For overheating issues, check the following
Coolant level. Check for any leaks
Obstruction in the radiator/hoses
Thermostat
Is the fan kick in ?
Did you bleed it right?!

Ka tends to trap a lot of air in the coolant system.

[TwoForties]

For overheating issues, check the following
Coolant level. Check for any leaks
Obstruction in the radiator/hoses
Thermostat
Is the fan kick in ?
Did you bleed it right?!

Ka tends to trap a lot of air in the coolant system.

-The coolant level is full and I flushed and filled the system a couple days ago.
-Over night the coolant level remains the same, so I don't think there are any leaks.
-Cleared the radiator of leaves and debris.
-I have yet to check the hoses.
-I took out and tested the thermostat, it opens when it's supposed to.
-The fan turns on immediately when I start the car and it stays on the whole time.
-Did I bleed it right? 1.) turn on the car. 2.) take off the rad cap and take out the bleeder screw. 3.) I fill the radiator with coolant until coolant squirts from the bleeder valve hole. 4.) then I screw in the bleeder screw and close everything up. Am I doing something wrong here?
It only doesn't overheat after I bleed it. The next day it starts again. Am I not getting all of the air out? Maybe there is a small leak that is letting air in, but not big enough to let much coolant out.
Btw, the coolant release bolt on the block doesn't go in all the way, because the last few threads are rusted. Maybe this has to do with it?

[spooled240]

Does the coolant in the reservoir get sucked back in after the car cools down? If not, you may have a leak where it's sucking in air on cool down.

[TwoForties]

Does the coolant in the reservoir get sucked back in after the car cools down? If not, you may have a leak where it's sucking in air on cool down.

I think I know what you mean, but i'm not 100% sure. But the coolant in the reservoir is at the same level that it has been, not more nor less.

[TwoForties]

Also while driving sometimes the temp gauge will be at operating temperature then will shoot passed the H, but then drop back down to operating temperature within like 10 seconds. Sometimes it fluctuates and sometimes it rises steadily. Is there a chance that the temp gauge sensor is bad, or can the coolant actually change temperature that quickly. All I can think of is maybe there are some small air spots that pass the sensor, idk.

[acslater9]

Have you tried replacing your CTS?

[e1_griego]

Bad grounds will make the temp gauge on the dash go wonky.

[TwoForties]

Have you tried replacing your CTS?

Sorry, but what's CTS?

[e1_griego]

The coolant temp sender.

[TwoForties]

The coolant temp sender.

Thanks

Have you tried replacing your CTS?

No, but i'll look into when I get paid next week.

[TwoForties]

Can someone explain in detail, step by step, the proper way to fully bleed the system of air? Please and thank you:)

[spooled240]

I think I know what you mean, but i'm not 100% sure. But the coolant in the reservoir is at the same level that it has been, not more nor less.

The coolant level in the reservoir should rise when the engine is warmed up then drop back down when the engine cools down.

[TwoForties]

I found a small leak in the lower radiator hose. I assume air can get into the system that way. So I assume that is the problem. Will get new hoses on Thursday:) Thanks for the help guys.

[TMann]

If replacing your hoses does not work, it could be your water pump. When the car is in idle the water pump might be working. But when the engine warms up the pressure builds up if your water pump is warn out it can start to slip. If the bearings in the water pump start slipping the water will not circulate like it is supposed to causing the engine to overheat. The fan can be turning fine but the fins on the water pump that circulate the water will not be turning. A lot of times you can open the radiator cap and see if the water is moving across the top of the fins.

[TwoForties]

If replacing your hoses does not work, it could be your water pump. When the car is in idle the water pump might be working. But when the engine warms up the pressure builds up if your water pump is warn out it can start to slip. If the bearings in the water pump start slipping the water will not circulate like it is supposed to causing the engine to overheat. The fan can be turning fine but the fins on the water pump that circulate the water will not be turning. A lot of times you can open the radiator cap and see if the water is moving across the top of the fins.

Okay thanks, i'll check that next if the hoses don't work. I think I might also have a problem with like the temp gauge or the grounds or something. Because I have flicked the cluster plastic in front of the gauge and sometimes it goes back down to operating temperature, lol.