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warming up problem


bandit22re
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i got a 96 pathfinder 3.3 L , auto trasmission . and i just changed the thermostat a month ago. it was stuck open i figured because it didnt put out much heat. and wouldnt shift into 4th gear unless it was really warmed up. it was a bitch to change the t-stat in this thing. when cruising at 60 mph in overdrive and my heater at med when its 20 degrees F it will drop gears and be at a higher RPM trying to warm it up again. not really like before tho. the heater seems to be warmer than before it had this problem. so i was thinking maybe the tranny cooler. but i dont really know much about that @!*%. if i start my car in the morning on a below zero day and immediatly hop on the highway and do 70 mph with no heater on; how long is it supossed to take till i can get into 4th? mine would probably take 10-12 miles at 3500 rpms somewheere round that. how can i fix this. and i get alot of ice on the inside of my windsheild some times in the morning. and my power windows always get frozen and wont open even when it hasnt snowed or rained.

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when it is below 4 celcius, i experienced that it is not eager to shift to 4th gear. or lets say overdrive. when it is warmed up, it shifts normally. it takes 10 miğnutes in freeway at that temperature. this seems normal operation. i put a nylon sheet infront of radiator to make it warmed up faster and it worked. it saves few minutes.

 

by the way my transmission started to shudder while shifting 3 rd to 4th gear, now is it in service shop for rebuilding. all internal mechanical elements will be replaced.

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well, considering how cold it is, it would be normal operation. You have to remember you have a fan thats always spinning (except at higher rpms) so all that cold air is being sucked through the radiator, hence why its not always as warm. SO, you should get something to block SOME flow to the radiator. I don't know if you have ever seen big semi trucks or school buses, but durning the winter they have those winter covers on front to keep the engines from cooling down too much.

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get a piece of cardboard and an exacto knife, then cut the cardboard so you can slip it in between the a/c condenser and the radiator.

 

this will act like a winter front but for way less $$, on my wd21 i cover about 2/3 of my rad and leave the portion open where the flow is interrupted by the aftermarket tranny cooler i installed. Works like a charm, and i did the same on my r50 that i had a few years back.

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FYI, the issue with not shifting into OD has nothing to do with the engine temperature, it has to do with the transmission fluid temperature. The torque converter slips to generate friction and heat to help warm the fluid to operating temperature. Once the AT is warm, the torque converter can lock. It sounds to me like it's just too cold out to get the fluids up to temp, so the others who have recommended some kind of radiator blocker are on the right track.

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ive been putting a grocery bag over half of the transmisson cooler and it seems to help. i just hope that it wont get too hot now and fskc up my transmisson. is there some kind of t-stat or valve on the tranny radiator? or does it just keep pumping it through? im pretty sure there was some kind of warning lite if it overheats. in case u tow alot. which half of the engine radiator is better to block? drivers side or passenger. i did passenger cuz the hose is at the top so i figured that i'd let the antifreeze cool a little first from the bottom hose (driver side).

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is there some kind of t-stat or valve on the tranny radiator?

 

No, the tranny fluid just keeps pumping through. Hopefully that grocery bag you're covering the AT cooler with isn't plastic. If it gets hot, it'll melt and then you'll be screwed. Better to cover it with cardboard or paper (or even thicker plastic, such as lexan).

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I know on my other vehicles that a lock-up torque converter will not lock up until the engine is in closed loop mode (Open loop = warm up cycle, closed loop = engine at some miniumum operation temperature). If this is happening to you, it could be: tstat stuck open, too low of a stat temp rating for your climate, temperature sensor failure, temp sensor signal not getting to the ECU. There may be other causes?

 

Cold front kit and block heaters are a great thing. If you have no block heater, you can buy a similar thing that installs in the heater hose or rad hose.

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I know on my other vehicles that a lock-up torque converter will not lock up until the engine is in closed loop mode (Open loop = warm up cycle, closed loop = engine at some miniumum operation temperature). If this is happening to you, it could be: tstat stuck open, too low of a stat temp rating for your climate, temperature sensor failure, temp sensor signal not getting to the ECU. There may be other causes?

 

Cold front kit and block heaters are a great thing. If you have no block heater, you can buy a similar thing that installs in the heater hose or rad hose.

 

On the R50 (at least on my '97), the engine can enter closed loop long before the transmission has warmed up. The TC lockup logic seems completely based on the AT fluid temp, not on other engine sensors.

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Good to know the pathy works a little differently, thanks.

 

 

Bandit - are you due for a trans fluid change? What temp rating thermostat did you install?

Edited by BowTied
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i heard that you should never change the tranny fluid if u buy a used car cuz itll fskc it up. unless u know it has been changed regularly. but i checked the level with the engine on after driving a mile and it was on the cold marks on the stick. and i think they only had one kind of t stat at advanced auto. dont know what the temp was, but i know it worked alot better than the one that was in there. that was a real nissan one. and i think the bag is on the end of the cooler. so the fluid is alot cooler by the time it makes it to that half. and its always cold here so it wont melt. its easy to put in and remove if i drive in the around city alot

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