Overheating... why?!

[SHINCHU]

I was driving my s13 up the freeway and just happened to glance down at the temp guage out of habit, and to my shock and horror, it was about 3/4ths of the way overheated. (. ./.) about like that. i immediately pulled to the slow lane and limped home doing about 50. didnt get any worse but it didnt cool down much either. i wasnt going 90 or anything. just doing a casual cruise at about 70. didnt hear anything, no leaks, nothing. just pure HEAT. i got home and let it cool down and eventually checked my coolant level. looked fine. no oil in the coolant. nice and green. checked the oil. perfect honey colored and full. now i get curious and pull the thermo out. original nissan so i replace it. fire it up. overheats just sitting in front of my house in neutral with just 3,000 rpm of throttle and no load. i get even more curious and change my water pump. same thing.

could this be... the head gasket? god i hope not. i just put this engine in 6 months ago. this is a KA24DE, btw. its not under boost. no cams. just intake and exhaust and a couple drift events. regular oil changes and have maintained it like i work for NASA. has anyone else had wierd overheating problems like this? my next suspect is a clogged radiator. had that problem on my ae86. another wierd thing is the coolant seems to rise and fall rapidly in the radiator when i took the cap off while it was idling. almost like a pulse. wtf is it? any useful tips and knowledge are greatly appreciated. thanks.

[MadChild]

Visually you can't really check the coolant level in the raditor, Make sure there is plently of coolant in the raditor. Also check all your coolant hoses see if there any slight leakage of coolant. If everything goes well, check the raditor...The raditor might be going bad or your water pump is not functioning properly. See if your fan is runing good if its not i suggest to up grade to a electrical one.

[Bill Roberts]

Use search and my name. I wrote an entire radiator primer not long ago. It will help you find out why.

Air needs to go through vanes, system must flow, thermostat must be open and block or radiator cannot be clogged, use antifreeze to raise your boiling temp and make sure the cap is clean or new.

that about covers it.

Most coolent problems are airflow and water flow conditions.

Do the search..it is your pal..I got very detailed in my analysis.

[old_s13]

1) When the car is cold, just make sure your radiator has coolant in it, open the cap and take a peep -- WHEN THE CAR IS COLD.

2) Let the car warm up a bit, you should notice pressure in the 2 radiator hoses.

3) Water pump is responsible for circulating your coolant, if that is not being done the car will overheat.

[kkw4p]

Take out your thermostat and see if that solves it. Your therm might be sticking shut. If taking it out solves the problem then boil your therm (in water) to make it open.. if it doesn't open, it's bad.

[240Stilo]

Originally posted by kkw4p
Take out your thermostat and see if that solves it.


Originally posted by Shinchu180sx
now i get curious and pull the thermo out. original nissan so i replace it.

He covered that one already. Read up son...:doh: :rolleyes:

[Eyescream]

Bleed the system. Jack the front end up and with the car warm bleed the system. Add coolant to bring you to level and you should be fine.

I chased a problem like that for days before I figured out what I wasn't doing right.

[Kid Zelda]

Plaese tell us you did not install the THERMO' backwards ! :aw:

[DuffMan]

I had a similar problem and it turned out to just be air pockets stuck in the system. Are you sure you are bleeding it properly?

This is what I do:

Fill it up until the burp hole overflows. Shake the engine as hard as you can by pushing on it from the side to get the air bubbles out. Run the engine for a few secconds and fill again. Repeat a few times until the burp hole overflows instantly when you add coolant.

[mbmbmb23]

Could the water pump be failing? I think some shops have a tool that sucks all the coolant out and pumps new through under pressure....and I think that gets rid of the air pockets.



-m

[MadChild]

I worked at a local shop around my area and they had that. But its mainly use for coolant flush so it might work

[TonyC]

I don't know if this would help you solve the problem but I had a similar problem in my 96 SE-R. I tried everything from bleeding, changing thermostats, to even chaning both the coolant temperature sensors. My "temperature" needle says it overheats in the car. I mean literally it goes over the "H" into no man's land. I was so worried that's why I changed all those stuff mentioned above. Well it turns out my temp gague might be screwed up. What I did was hook up a Techtom MDM-100 to my OBD-II port and set the setting to water temperature. It turns out my fans turns on (FWD) at the FSM indicated 212 degrees F, with the G20 ECU I have on I believe it kicks on at 210 degrees F or something. During normal driving around town (35+MPH), when the needle would be literally on the "H" I would hit a very normal mid to high 180 degrees F. I don't know which to trust, but since the Techtom reads straight off the ECU, I would tend to trust that more. Just my $.02.

[Eyescream]

It's possible the temperature sending unit is screwed up, it's not the most accurate piece of instrumentation in the world, after all.

Just bleed the system (make sure the car's good and warm so the thermostat's opened up so you can really bleed ALL the air out instead of just what's behind the thermostat, and see if that helps.

The first S13 I had had this exact same problem and I fought it for a week before I tried bleeding it.