very WEIRD overheating problem

[j00ni3]

i was driving my friends s14 zenki bone stock ... absolutely no mods...

auto ...

now i was driving down i80 and it was fine... got on the 95 pulled out on pal park. i got onto broad ave and was at a red light...

no exhaust upgrades so i couldn't hear it ... but then i felt the car trying to nudge forward... so i looked at the tac and it was going a little bit over 1000 rpm .. which was weird with no a/c or anything on... and i looked right over to the temp and it was over heating like crazy~~ ...

so we stopped it and let it cool ... turned it back on and then drove.... it was fine for like 5 min then again... so my friend says to me ... it's ok ... just rev it a bit... so i slap her into neutral and i rev it around 4000-5000 ... ( i don't know if that was good but hey not my car ) and the temp gauge started to go down ... so i was like.. hum... ok maybe system is not bleeded... but after that it ran FINE... for like 4 hours ... in local traffic/ and highway

then we went to his house... i flushed the system twice over.... put in water wetter and distilled water... no anti ...

i bled it on his driveway... ( steep ) with theheat on and everything ... so only coolant was coming out of the bleeder hole... no air

we drove... for about 20 min and then let it cool ... and put it ontop of his new cement driveway to see for any leaks...

nothing...

so he drove.... and about 10 min later... B"OOM starts to overheat like a mofo..

so he s tarts revving which i wasn't really fond of... and then it cools down...

now we drove her back and checked for any leaks on a jack and everything ... nothing... checked for oil in the coolant ... NOTHing ...

when we start the car with the rad cap off... it doesn't like GOOSH out... it just like.. ripples a bit.. but that's it ...

edit :: also ... checked his compression at my house... IT Was ALL FINE... no abnormal compression in any cylinders...

edit :: my friend took out the clutch of the fan and checked it like the fsm states.. no problem ... fans kick in at right temps... everything's fine~~~ AHHHHHHHHHH driving me crazy

what can it be? help

[MELLO*SOS]

Try removing/checking/replacing the thermostat?

[g6civcx]

Do a pressure test on the cooling system. You may have leaks.

[s14xman]

so you checked the clutch fan, but did you check the rad fan? if it cools after reving it, it could be your clutch fan kicking on at high rpm's and cooling it down picking up the rad fans slack

[aznpoopy]

basic checks...

thermostat
coolant temp sensor
waterpump
clogged rad
etc...

if everything else fails you probably have a small break in the headgasket... just happend on a friends' dd 93 cavalier. new rad, waterpump, thermostat, temp sensor, hoses, etc... runs fine at idle and overheats under load. no smoke at all, anywhere. final diagnosis = blown headgasket. really gay...

so you checked the clutch fan, but did you check the rad fan? if it cools after reving it, it could be your clutch fan kicking on at high rpm's and cooling it down picking up the rad fans slack

i may be totally off base here, but the clutch fan is the rad fan... the stock electric fan is an accessory fan that only kicks on when the a/c is on. or that's what i thought... maybe i'm wrong.

[j00ni3]

checked everything just now...

no problem watsoever with anything ... electrical and mechanical...

may be it is the headgasket...

but i found no oil in the coolant...

also ... with a broken headgasket would it cool down after revving hard?

i mean i dont' get that part tho... a broken hg means that it will just overheat crazy after a while no ? and not go down when revved hard... idk

educate me ...

thanks guys again... but all in all everything you guys said didn't work

[Frenzy13]

Had a problem similar to this on my 92. I went through and replaced everything; ie clutch fan, radiator, therm, and hosing, bled the crap out of it and still it happened. I would pull over and rev the motor to about 5k and hold it there and low and behold the temp would always settle back down. The wierd part was that she was never boiling hot even the she should have. Long story short it turned out it was the temp sensor for the guage that was fowled and the electric fan wasn't kicking in.

Found out the hard way that you do need both of them, at least on mine. The electric kicks in periodically to add to the cooling, also I confirmed it when I was driving down I5 to LA and the alternator went out and she over heated. Anyways here's my 2 cents

[MELLO*SOS]

turned out it was the temp sensor for the guage that was fowled and the electric fan wasn't kicking in.

Might want to check the ECT sensor also. GL

[j00ni3]

sorry but what's a ECT ?~ hehe... ^^

[s14xman]

i may be totally off base here, but the clutch fan is the rad fan... the stock electric fan is an accessory fan that only kicks on when the a/c is on. or that's what i thought... maybe i'm wrong.

i'm pretty sure it is the rad fan because i ditched my clutch fan long ago and the rad fan kicks on at high temps with no a/c on, you can hear it kick on.

[j00ni3]

yea... the e fan works fine..

so ECT?~... what's that?~ hehe ... *^^*

[slider2828]

Every think it could be a water pump issue or belts?

[Frenzy13]

E.C.T.
Engine Coolant Temperature sensor

If I'm not mistaken this is the sensor that goes to the ecu. THere are 2 sensors right after the inlet hose for the radiator. The first one is the sensor for the ECU and the second if for the gauge.

Could be wrong though. Going off memory right now and the brain won't jumpstart today! Good luck

[MELLO*SOS]

Yeah sorry, there is one for the gauge and one for the ECU, test them both maybe the one for the gauge is just out of whack and you're not really overheating?

[j00ni3]

oooooo ok thank you frenzy... me and my friend did a full diag.. on the car today since 830am est time till now ... 4 o clock... no leaks... no bubbles... no nothing~~~~ AHHHHHHHHHH

thermostat good
waterpump <-- brand new
fans good
compression good
rad no clogs..( new oem .... idk why i think the old owner had this problem so got it changed at a dealer or something)
voltages ran fine on all sensors ... no shorts or anything anywhere ... checked all voltages... also knew it wasn't electrical before hand because when the gauge goes up the overflow tank... bubbles and spits out water throught that hole next to the cap





me and my friend looked at eachother and actually came to a conclusion... it might be that the engine is just crapped out... no ? i mean maybe the cylinder walls are scratched badly... but compression is good .. so maybe not?

also ... like i asked earlier will a blown headgasket really overheat occasionally and settle down on high revs? ... idk ... does it ?

wow... he had this car for like 3 days hahahahah i feel bad for him and my hands... can't see my hands... its so black it blends in with the keyboard HAHAHAH.. ( don't like using gloves ) like the feel of metal hahaha ... * weird fetish *

anyone... suggestions? and please don't say cylinder walls or head gasket~~~~~~ AHHHH

anyone ?

[aznpoopy]

if everything checks out and it's still overheating, i say a blown (albeit only slightly blown) headgasket. but i'm not there running the tests... go over everything again and cross your fingers.

[Frenzy13]

I don't think a blown headgasket would calm back down. Just because of the nature of the beast. I've been trying to think and it's got me stumped just like mine did. If you haven't replaced the sensors you might want to. They aren't expensive that expensive I think for both of them it's like 60 bucks. Also try using a bottle of the coolant system flush, you might have a little buildup inside the block somewhere.



Also you said you compression tested what did that come back as??

I'll keep pondering it and try to help you out as much as I can

[OdessaS13]

voltages ran fine on all sensors ... no shorts or anything anywhere ... checked all voltages... also knew it wasn't electrical before hand because when the gauge goes up the overflow tank... bubbles and spits out water throught that hole next to the cap

did you check relays? maybe bad contact somewere

[j00ni3]

like around the 160+ - like 5 marks from 1-4 ... did i read that correctly ? hehe..

cranked at wot..

odessa... yea... that was actually the first things i checked when i started going over all elec. stuff

[Frenzy13]

like around the 160+ - like 5 marks from 1-4 ... did i read that correctly ? hehe..


With numbers like that I'd say that the head gasket isn't blown, because usually a leaking headgasket will drop compression a little bit out of spec.

[j00ni3]

yea i know what your talking about frenzy... i mean your's wasn't blown either right ? ... you just had something else.... but that something else i ca'nt find it ~~~~~~ ahhhhhhhhhhhh

[Frenzy13]

yea i know what your talking about frenzy... i mean your's wasn't blown either right ? ... you just had something else.... but that something else i ca'nt find it ~~~~~~ ahhhhhhhhhhhh


No mine wasn't blown, in fact I got a compression of 178 across the board and the motor is running great. Its something. Honestly I drove mine for about 5 months before I finallly found out the problem. I just planned that where ever I would go it would take an extra 10 min to pull over and make the engine cool down. So long as he doesn't bang of the rev limiter he shouldn't cause a much damage if at all.

How do you know that therm is good? Try pulling it out and driving with out it. Throw it into a pot of water that you have on the verge of boiling. If it opens try driving without it, it might help the problem. If it doesn't open you know its bad. On my friends 240sx, he had an air buble that we couldnt get out of the block, it would get stuck right behind the therm and it wouldn't open. He drove the car without the therm in for a week and it never overheated. We put it back in and then bled again and it never overheated again.

Also I know that a lot of people have had problems bleeding these darn motors and have ahd to take them to Nissan to have them pro bled. I personally spent like 40 min bleeding mine. Jumping up and down on the car to force all the bubbles out the block cause its easy to get them out out of the radiator but not from the block.

Keep pondering for you and I'll talk to my friends now too. Wish you luck. Let me know if you figure it out.