KA24DE overheating

[corey170]

My car is overheating periodically (once every couple weeks) after about 20 minutes of driving. When i feel the thermostat housing it doesn't feel very hot, but the upper rad hose is very hot, which leads me to believe its the thermostat. Normally I would just replace it without thinking (so easy on the DOHC compared to the SOHC), but the guy who I bought the car from last month said he had just replaced it. Is it possible he installed it wrong (i.e. jiggle valve in the wrong position) or could this be a water pump problem?

additional details:
After letting the car sit (engine off) for about 5 minutes its cools off, then when started it doesn't overheat again and drives fine for the rest of the day. Also, coolant is coming out of the rad into the reservoir and the coolant is not dirty (nice and clear; green color).

Any help?

[biggie]

Sounds like the thermo is sticking occasionally, would replace. Could have installed wrong or got a bad one.

[SemperWrenchin240SX]

not sure if this is totally correct but the lady I bought my 240 from had issues. Hell the top of the radiator is still cracked and filled with some sort of putty to seal it...terrible job. Anyway I pulled the thermostat out completely so its always circulating. Granted on cold mornings it takes a bit longer to heat up but that is my only draw back. Other wise pull the hose and check to ensure it is facing the correct directing. If im not mistaken its stamped "ENGINE SIDE" or something like that. Then obviously fill and bleed your system.

[corey170]

OK, so I changed the thermostat on the weekend and the car is still doing the same thing. I tried bleeding it several times and I'm still getting the same problem. Does anybody have any idea what I should replace next? I'm gonna go with rad cap because its so cheap/easy. Any other insight would be very helpful.

Extra notes: when it does overheat, its always at the same time (i.e. ~20 minutes after driving). I know this from me pulling over at pretty much the same spot every couple days on my way to school.

[ricebike]

but the upper rad hose is very hot, which leads me to believe its the thermostat...

i thought the thermostat is linked to the lower radiator hose

bleeding the system is a PITA for nissans... i'm thinking of getting one of "those burp funnels" for my next cooling system service
(i LoLed at the way the FSM caters into burping the cooling system for the minivan~ you got to do a makeshift IV jug with a windshield washer bottle and some hose)

i guess if the gaskets on the rad cap is bad, doesn't hurt to change it as part of the maintenance.

are you using OEM or aftermarket t-stat?

from another site:

I did more research and found that the stock Nissan thermostat is a lot different from the crappy Autozone OEM ones. The bleeder hole is much higher and has a bigger bleeder to fix the bleed/bubble problems with these motors.

So in the meantime, since I am too broke to buy parts right now, I drilled a 1/8in hole in the top of the thermostat above the bleeder hole in the OEM one from Autozone. I used a large funnel in the radiator to bleed the system and utilized the bleeder valve again on the manifold.

...the nissan was more bulky, had a larger coolant flow hole, as well as larger air bleeder hole. It operates a lot better than the autozone..thing.

...autozone bleed hole is real close to the middle vs the nissan being near the edge

I was lucky that i've used a stant / aftermarket one & has bled the system properly, using that bleed bolt by the coolant sensors, jacking it up, heat on full HOT, etc.

the next time that i'll be going to change the t-stat will be to either drill a small hole on the aftermarket, or get an OEM one.

PS: is the cooling fan working? belt-driven clutch fan ~ the silicone,oil inside may have bled out & it's easy to diagnose by putting your finger in the center of it & check if the fluid leaked out of that clutch



when i was guessing why the fan wasn't moving alot of air when hot, i stuck my finger around the center of that fan clutch and felt the oily residue that had leaked out of the unit...

if you have jury-rigged electrical fans on it, then disregard the last part of my post & verify if the fans are working

[corey170]

No fluid leaking from the fan and I have popped the hood while overheating and the fan is spinning. Does anybody have any idea on what this could be? it always happens at the same time and it stays at working temp for the first 20 minutes or so of the drive. I was going to say water pump but there is no leakage coming from it and it doesn't sound bad at all.

Any help at all would be appreciated...

[moso]

how clean is your radiator? use a pressure washer and blow it out from the motor side. I second using genuine nissan thermostats because most aftermarket ones are smaller and dont flow enough. the fact that it takes so long to overheat is what trips me out because the ka warms up super quick. your getting some sort of restricted flow, clogged radiator possibly, failing waterpump, too small thermostat, possibly a collapsed hose ( i have seen fuel line collapse internally).

[LDB477]

I have had the same problem for a few years now. Same symptoms - no leaks, happens after a few minutes of driving, then I rev my engine to "help the flow" and the needle drops down slowly to the middle. I've tried replacing the thermostat as well and that didn't change much. If it was the water pump that would really surprise me because it is only that impeller driven by the pulley.

[corey170]

OK, so I changed my rad cap and water pump. That was on the weekend (5 days ago) and I have been bleeding the system every morning before I drive to school. It seems like a lot of air comes out each time, leading me to believe that air is somehow getting into my cooling system. I didn't bleed it this morning because of the weather and it overheated again on the drive home.

Any ideas?

[Canseri]

Remove the jiggle valve drill two small holes one on each side (the top inside circle) about 1/8 inch no larger for air to pass. My car (95 240) was overheating on 85° days here in AZ. I have since driven in 115° days and i have no water pump mounted fan, and my radiator shroud is mangled, and still I have no issues overheating. If your radiator is crap replace it. Also of note my car warms up in two miles even on 50° days. So my thermostat still does its job keeping the engine at its operational temperature

[corey170]

Thanks for the reply,
I doubt the hole in the stat will do anything because air isn't trapped, its just getting in somehow (if it was trapped then it its about 2 liters of air over the last couple weeks and i doubt that). Also the amount of air seems to be consistent every time I bleed the system, like it reaches a equilibrium mixture then stops. Is there supposed to be a little bit of air in there? If so, how does it get in?