overheating questions

Post by **97gesex** » Mon May 24, 2004 7:03 am

ok, the car is my friends 91 240sx se. the car is overheating after driving about a mile down the road. she brought the car over and i put in a new water pump and thermostat. the thermo i got was a 170 degree one, and i boiled it to make sure it was working (dont trust autozone very much). i also pulled the radiator and flushed it out. i looked on here and burped the system as everyone describes how, but the car is still overheating. when i get back from driving it down the road, the upper radiator pipe is extremely hot, but the lower one is completely cool. i also made sure fan on the end of the water pump is working and the one on the radiator itself is working. i also felt around in the floorboards to see if it was damp or anything to see if the heater core could possibly be bad. no luck there either. the car is not losing coolant. checked for leaks and didnt find any, and after the car has overheated, the radiator will still be full of coolant. also, no oil in the coolant or vice versa. im stumped.

thanks very much in advance for any advice or info.

Post by **NISTECH** » Mon May 24, 2004 7:03 am

really dumb question here but are you sure you have the T-stat facing the correct direction [ not in backwards]? if thats right you have to have an air pocket still.

Post by **97gesex** » Mon May 24, 2004 7:03 am

the main body of the thermosatat (the part with the springs and all) is inside the block, not the little neck part that you unbolt to get to the thermostat. ill just keep trying to burp the system and hopefully thatll do it. it just seems like coolant is not circulating through the car.

Post by **DAEDALUS** » Mon May 24, 2004 7:03 am

Another far out question: Is it possible the belt may be routed incorrectly, such that it's driving the water pump the wrong way?

Post by **97gesex** » Mon May 24, 2004 7:03 am

i just put the belt back on the way it was when i took it off. its is the belt that runs the water pump and the power steering off the crank pulley.

Post by **NISTECH** » Mon May 24, 2004 7:03 am

I just remembered something that I seen about a year ago on a 240. The fan was installed backwards on the clutch causeing the air flow to blow out toward the front of the car and it overheated quick when you would put the car under load. see which way the air flow is going when you throttle the engine. It should be able to suck a peice of paper against the front of the A/C condensor[in front of the radiator]. If it doesnt flip the fan around.

Post by **97gesex** » Mon May 24, 2004 7:03 am

when i reinstalled the fan, i just looked at the oxidization on the metal part and you could tell which way it went on. ill double check that though, never hurts.now a possibly dumb question regarding the radiator hose routing:the upper radiator hose goes into the head where the bleeder screw is and the lower one goes into the water neck/thermostat housing correct?i was just pondering what could be wrong and wondered by chance if somehow i mixed the hoses up. i looked at how the hoses were routed on my gsx, and the upper went into the thermostat housing, making me wonder if i ran them wrong on the 240.i also rebled the coolant system by elevating the front of the car, starting it and letting it get up to normal op temp with the heater on full blast. then i took out the bleeder screw and took off the radiator cap. it was blowing bubbles for about 2 minutes or so, and i was just adding coolant until they stopped. unfortunately during this i was bombarded with rain, so i havent had a chance to drive the car since ive done that, but im hoping that was the correct way to do it.

thanks a lot for the suggestions so far, keep them coming.

Post by **droll** » Mon May 24, 2004 7:03 am

Since the upper hose is real hot and the lower one is cold I would think it to be a flow problem more than anything else.

Post by **droll** » Mon May 24, 2004 7:03 am

Are you getting any overflow into the coolant overflow tank?

Post by **NISTECH** » Mon May 24, 2004 7:03 am

have you had any head work done on this car recently? The way the coolant flows is into the block then up into the head at the back of the head then back out to the radiator. If there was a restriction in the head gasket at the back it would not allow coolant to pass into the head.

BTW you dont remove the bleeder screw while the car is running, you do it when you are filling it up initially. put it back in then start the car with the cap off and a special bleed funnel where the radiator cap goes and it being elevated.

Post by **NISTECH** » Mon May 24, 2004 7:03 am

coolant flow layout

Post by **97gesex** » Mon May 24, 2004 7:03 am

well, i ran the car when i got home this morning. it was raining pretty hard after i got done bleeding the coolant yesterday. it ran fine and never got hot. the back roads around my house are really crappy, but there is about a 5 mile stretch where i took it up to about 90mph for as long as i had road to do it. never got above the normal mark. the girl drove it home, which is about 20 miles from me, and she never called to say it overheated, so i assume everything is good to go.

thanks a ton for all the info and suggestions that everyone has posted. you guys have a great community here, matching the dsm one im currently a part of. nice to know theres still places around where someone new can just pop in to get some help. thanks again everyone.

Post by **ricebike** » Mon May 24, 2004 7:03 am

off topic: what is the dsm group u belong to? my lil brother just got his 91 eclipse & i can't find any good ones...thanx

Post by **NISTECH** » Mon May 24, 2004 7:03 am

no problem guy. Your welcome aboard anytime. Talk the girl into getting on board. even she might find stuff interesting on here about her car.

Post by **97gesex** » Mon May 24, 2004 7:03 am

nistech- the girl is 35, and not much into cars. she just likes them if they run good.

ricebike- tell your brother to try dsmtalk.com and dsmtuners.comthey have some decent info on those sites for anything from engine work to paint jobs. for a more serious, mechanically oriented site, try teamnabr.com. be warned though, some of the mods on that site are really tough on people who post questions without doing any research beforehand. they will all tell you to go to vfaq.com and find it there. vfaq.com is one of the best resources for dsm owners on the web. magnusmotorsports.com and roadraceengineering.com also have some really good tech info on engine swaps and other things like that. good luck to him.

Post by **ricebike** » Mon May 24, 2004 7:03 am

thanx for your reply

& nissan tech thanx for your contribution on making this group one of the best ones on the net:ylsuper ever heard of http://www.batauto.com that's another resource i use for my family's cars if i'm stuck on something...

another thing to add: when I had to replace my radiator... there was soo much debris <leaves n stuff> lodged between the rad & the A/C condensor ~50% was covered over the years that this may also affect the cooling efficiency...

i now make it a point to check in between them every time i do the preventative maintenance coolant flush from now on!

Post by **NISTECH** » Mon May 24, 2004 7:03 am

dude I will be 35 in a couple months and I hate cars yet here I am

If she came around at least I wouldnt be talking to children...lol

overheating questions

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