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Discussion Starter #1
1991 Nissan Pu hardbody 4 cyl. 2wd

Last winter I replaced my Nissan thermostat with a Stant(same temp rating). It was the more expensive one that is designed to stay open if it failed.
The old Nissan thermostat still worked but the rubber seal was worn out allowing continous bypass of cold water and making it a long time before I could get hot heater air.
One thing I noticed right away with the Stant, it seemed the running temp was higher with the gauge a bit more that half way over.
This spring, the first 90 degree plus day, I was going down the highway (without AC) and saw my gauge way over close to max. I had to run the heater on full blast and reduce speed to about 45 mph to bring the water temp down to a safe reading. What a long miserable trip.

I had thought the Stant was not opening all of the way it should.
I pulled the Stant out, and compared it with the old Nissan thermostat that I still had around. Hey! I noticed the Stant had a much smaller valve opening diameter than the Nissan one. I felt the smaller opening would restrict the flow as compared to the OEM one and that is what caused my problem, could I be correct?

I tested the Stant on the stove. It opened all of the way when the water started to simmer.

I took the Stant back to the auto parts dealer. They had another brand but it also had the small opening. I went to Autozone store. Their thermostat also had the small opening. What is with these small openings?

Does anyone know what the deal is? Is there something wrong with my pickup since it did not cool with the Stant? I have a good mix of antifreeze in it.

Am I going to have go to the dealer to get replacement with the same size as the OEM?

I was going to replace the thermostat in my 1997 Nissan pu 4cyl also. They sold me an identical Stant to the one I got for my 1991 pu. So I took that Stant back also.
 

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check your radiator cap. It can make your car overheat as well if it starts to fail. I had a overheat problem cause whenever I drove my truck during the day it would overheat within the first five miles from my house. But when I drove it at night it never over heats at all. I thought it was the thermo so I then changed it. It still happen. I redid my rad flush and it still did it. I went out and got a new temp switch and guess what it ? It still did it the same thing. I then noticed that if I let my truck warm up in the drive way to a complete warm up until it reached overheat a hour before I left and then turned it off for about a hour or so. Then come out and restart the truck it didnt over heat until I got out on the highway in which the temp would raise up a little but not much. Well I decided to clean everything and while I was at Autozone getting new Rad fluid I opted to get a new Rad cap. As I left the store I but the new rad cap on and it didnt overheat not one time all the way home. I have sinced driven the truck for more then 2 weeks and not one overheat yet.
 

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The Stant thermostat is a piece of crap. I've used them on KA24 motors and they tend to cause more overheating problems. Get a brand new OEM unit from a Nissan dealer.
 

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Discussion Starter #4
Thanks for the helpful replies. I had overlooked the cap. I see that it is a Nissan cap. (Wow could it still be the original 17yrs old?). Upon inspection I noticed the rubber is bleeding a bit so it must have been in there quite a while. I am going to replace that also for reliability.

This morning I stopped off at Orielly auto parts and they sold Murray thermostats. The one for my truck had a small diameter opening the same as the Stant so I passed.

I then went to the dealer and forked out over twice the price of an aftermarket failsafe for a Nissan genuine. What I got was thermostat with an opening that was better. The diameter was only 1/16 less than the old original. Even though it had Nissan stamped on it, it looks very much like a Nippon brand.

At home I stove tested the New Nissan stat with the the old orig.
Both opened up at water simmering. The coil on the old one completely scrunched together, thus opening wide. The new one was not very impressive at all. It opened it tad slower and the coil windings never quite fully came together thus the opening had a gap size less than the old original. I guess that still is considered working properly though not quality in my opinion.

part number of the new Nissan thermostat - 21200-0C811
 

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Discussion Starter #5
Can someone please tell me where my temperature gauge needle should read on my 91 Nissan pu 4cyl. when at normal operating temp?
The Nissan thermometer is the standard 76.5 C. Consider the outside temp about 75 deg F and not using any AC.
All I have on my gauge is a 'C' on the left and 'H' on far right.
When the motor has got warm, the thermometer has the needle about straight up 12 oclock position. Seems a bit high to me.

Yesterday afternoon in traffic and 94 deg air temp, The needle started creeping way past the 12 oclock position towards High. I do not know what the problem is.
 

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There may be air in the coolant system. You need to purge the system of air every time you drain down the system. There should a '"burp plug" where the top hose connects to the head.
 

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1991 Nissan Pu hardbody 4 cyl. 2wd

Last winter I replaced my Nissan thermostat with a Stant(same temp rating). It was the more expensive one that is designed to stay open if it failed.
The old Nissan thermostat still worked but the rubber seal was worn out allowing continous bypass of cold water and making it a long time before I could get hot heater air.
One thing I noticed right away with the Stant, it seemed the running temp was higher with the gauge a bit more that half way over.
This spring, the first 90 degree plus day, I was going down the highway (without AC) and saw my gauge way over close to max. I had to run the heater on full blast and reduce speed to about 45 mph to bring the water temp down to a safe reading. What a long miserable trip.

I had thought the Stant was not opening all of the way it should.
I pulled the Stant out, and compared it with the old Nissan thermostat that I still had around. Hey! I noticed the Stant had a much smaller valve opening diameter than the Nissan one. I felt the smaller opening would restrict the flow as compared to the OEM one and that is what caused my problem, could I be correct?

I tested the Stant on the stove. It opened all of the way when the water started to simmer.

I took the Stant back to the auto parts dealer. They had another brand but it also had the small opening. I went to Autozone store. Their thermostat also had the small opening. What is with these small openings?

Does anyone know what the deal is? Is there something wrong with my pickup since it did not cool with the Stant? I have a good mix of antifreeze in it.

Am I going to have go to the dealer to get replacement with the same size as the OEM?

I was going to replace the thermostat in my 1997 Nissan pu 4cyl also. They sold me an identical Stant to the one I got for my 1991 pu. So I took that Stant back also.
i had that same problem with my ka24de. wat i did to resolve that problem was to simply remove the thermostat and now it takes a while to reach its normal water temp
 

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Can someone please tell me where my temperature gauge needle should read on my 91 Nissan pu 4cyl. when at normal operating temp?
The Nissan thermometer is the standard 76.5 C. Consider the outside temp about 75 deg F and not using any AC.
All I have on my gauge is a 'C' on the left and 'H' on far right.
When the motor has got warm, the thermometer has the needle about straight up 12 oclock position. Seems a bit high to me.

Yesterday afternoon in traffic and 94 deg air temp, The needle started creeping way past the 12 oclock position towards High. I do not know what the problem is.
I have the same truck/engine and my gauge doesn't go much further than about 1/3.
Do you still have the original rad? Mine slowly clogged up internally causing the engine to run hotter and hotter untill I figured out what was wrong. Replaced the original alum. rad with a brass and copper one. No problems since, 10 yrs. later.
 

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Discussion Starter #9
Thanks everyone for your replies. My problem still exists somewhat.
Afternoon air temps now around 97 deg. here.
I tried running withought a thermostat and water only. The guage ran around 12 oclock position then climbed up to about 3/4 way when in the city.
I had flushed the system with the Prestone superflush leaving it in there while running to the city and back and over night. The radiator appears to be very clean on the inside.
The hoses all look good. I put on another cap. It hold in the pressure. Still no help.

Every aftermarket thermostat I looked at, the opening was smaller than the original. I even bought one from the dealer and the clerk said it was a subsitute part number. That thermostat appeared to be a Nippon with a Nissan stamp on it. The opening was not quite a big as the original and testing it on the stove it did not open near as big as the original, so I took it back.


------MURRAY 4216 THERMOSTAT-------------
I finally found the best thermostat for the truck. A Murray Plus 4216. Orielly had the 180 degree (4218) in stock but I had to special order the 160 degree (4216) which is what I wanted.
The best part about this thermostat is that the opening is even a tad larger than the original. The box says this thermostat is high-grade stainless steel and made in Germany.
I removed the rubber gasket so the thermostat will fit fine in my truck and used silicone to seal the cap.
This thermostat is for application '94 Camero Z28 w/alum heads.
---------------------------------------------

After installing the Murray 4216 and antifreeze, the truck guage needle is still climbing to about 3/4 way. I think my antifreeze mix is too rich. I am going to correct that but I do not think that it will solve the problem.

Thank you ROGOMAN for telling me about the burp plug. I just looked and found it. never noticed it before. I will try to burp it and see if there is any air left in there.

mandy240sx - running without the thermostat will improve the flow but it will take forever in the winter time to warm the engine up to where your heater will work.

jmcduff - Yes I have the original Aluminum radiator but it looks very clean looking inside the cap and water flows thru it fast.
Where would I find a copper or brass radiator?
With the price of copper now I am scared to ask, how much?

I am running an aftermarket waterpump from Orielly autoparts lifetime warranty. From what I remember, I think that pump had a smaller impeller in it. Has anyone noticed this on an aftermarket waterpump. Seems like that would slow the flow and make the engine run hotter. I am reluctant to pull my water pump off and check that to be sure. I also do not have a stock pump or specs to compare it with.
 

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Hmmmm. If your rad is flowing fast it must be okay. I wasn't sure replacing mine would fix the prob, but luckily it did. The passages were narrow on the original so any gunk build up really slowed things down.
I went to an auto parts store and they said they could get either alum. or brass + copper. The b+c was about $200 back then. The alum. $100 or so more. Don't know what either would cost today.
I suspect the water pump in your case. But I don't have any knowledge of what the problem with it could be.
 

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There may be air in the coolant system. You need to purge the system of air every time you drain down the system. There should a '"burp plug" where the top hose connects to the head.
before you do this, have 3 prestone 50/50 coolant jugs. good bang for your buck. 2 for refill, 1 if you spill one or if you didn't drain the whole system. if that's still not enough, throw in some water between jugs. heh, just a lil

i was waiting for that qoute to be said. i put in an Autozone thermastat a ways back in my 240, nearly right after i got it. also rebuilt the front calipers (but some ahole that sold it left out an outer discpad and so i had to jb-mofo'n one on there.. never moved), tried to rebuild the rear calipers but after 60 bucks spent on trying to build the tool to do it, i said screw it and spent like 120-150 on brand new ones, then brake lines were changed... just the cheap black rubber ones, new, (well hidden, and not noticable beyond your 6k rims), bleed the lines... ...don't let me get into playin with old KA clutches. there's plenty of guys on here that know all about the direct clutch mod. "gettin rid of your box?"

On the thermastat, I thought the same thing with the smaller hole. But got the idea of there being air in the system because the Bleeder Bolt is so easily seen on the KA's Intake~~first port to you, just left of the Mating Surface that bolts onto the Head~~
you know those nice airtubes that you use to put bubbles in your fishtank?.. grab yourself a set of those.. all sizes from uber small to radiator hose size. ;] then ya got yourself a ton of any-sized, component vacuum system.. once you get the pump.
another way.. get a Vacuum Pump Kit like 15-30 $ at Autozone.
those smaller fishtank airpump hoses (the ones you attach the blue filterstone onto and drop into the tank?) are all about the same size as your..
Brake Bleeders
Clutch Bleeders
blah blah

well the reason i brought up the fishtank tubes instead of saying just go get a vacuum pump kit, is cuz the small size airpump.... comes with that blue filterstone thingy.... knock the blue filterstone thingy around till you come up with just the black hose attachment the blue filterstone thingy is glued to to attach to the hose... *flexes fingers* ...you use that hose that still has the black filter attachment still there, and attach the other end of the hose to an adapter to where you then can attach a small funnel...
thaz how you get the last of the air out.

the lil black thingy fits perfectly into your open Coolant System's air bleeder.

a vacuum pump kit's adapter also makes a nice seal.

but this is all the details... lol

WHEN ADDING COOLANT TO YOUR CAR, ALWAYS REMEMBER TO MASSAGE YOUR HOSE. ;]

pour coolant into the radiator.... it fills... is this the highest point in the coolant delivery system? no.

It's the Intake just before it attaches to the Head. There is a Bleed Port.

Make sure it's closed. now.

when the Radiator fills this time and everytime there after...
squeeze/massage/whack your Upper Radiator Hose... when you keep doing this.. gurgling will occur. ;] along with swallowing. heh heh! man i'm a lil "drunk" right now.

if you have a funnel sticking out of your rad cap that was pushed down hard enough to where it stays and holds fluid in... pour yourself a small pool.

**that is now the highest point in the coolant delivery system**

You got that Bleeder Valve open right? open it. ha, just kidding. don't. lol, not yet.

you will start to see the coolant lower... and..
a: gurgling,
b: moaning from having to do something, and
c: bubbling occurs...

oh and d: squirting from the Bleeder Port if you didn't keep it closed.

once it stops sucking in more coolant..
ONCE YOU STOP SEEIN BUBBLIES.
let the rest of the coolant in your funnel fall to the ground. ha.. for you eco lovers.. put a oil dran catch that's colored yellow underneath your car and catch it. duh.

leave the cap off! let it sit there with coolant aching to give your kids cancer via drinking water.

The Coolant System Bleeder Port... bolt. is now removed. that's right...
Open ''er Up!

that new homemade (engineered.. damnit), Funnel w/ the Fishtank Tube (or vacuum kit tube) goes into the open (hopefully not squirting yet.. i know, lame.. sux... but i'm the one that made her ...you know.. so i tell you how to do it so you can't. HA!) ....Coolant System Air Bleed ..threaded hole, hold the funnel up, fill the funnel and just hold it, trying to not get the waterfall effect where it rolls down your arm, armpit, and eneviteably to the pants. the weight of the coolant you put up top should push down and let those remaining bubbles come up to the funnel. *waits... waits...* *looks around and waits* wtf.. gd ...mit.. good school. ;]

entre: buddy happy and willing to piss off g/f by getting drunk and greasy with you!
:hal:
lol ..said buddy: more massaging can help...
ahh haha ...good jd n coke. lol

NO!.. lol. tell him to turn the key to on.
now you!
make sure the coolant doesn't go below the funnel and lower into the tube... in any Vacuum procedure, this is bad.. means you're sucking in air, instead of fluid like you're supposed to be.

if it gets low.. hit it up. goes too fast... turn it off.


air isn't too bad in the system .. if it's only a little. changing the thermastat and watching two coke bottles worth of coolant pour out before you had the yellow oil drain pan waiting.. is bad. ha, caughtcha. tree-killer! *told ya he'd get some on the driveway*

DO NOT ALLOW THE COOLANT TO SINK FARTHER THAN PAST THE FUNNEL WHEN YOU ARE FILLING EITHER SIDE!! this is similar to any other hydralic system.. AIR INSIDE IS BAD!! REAL BAD!! brakes fail, suspensions fail, active suspensions fail, clutches fail, etc. this is a lil different though, it can live with some air.. it just sorta moves cuz it's so small
and then it just sorta hovers ~~the steam~~ in the radiator.

A coolant system can't operate with air in that own circulatory system, if you have enough of it. There's is no coolant flow. It just collects in the low points and splashes around instead of flowing with the engine (which is exactly what you want your coolant to do... just like any other system, the tighter it is, the quicker the response is) ...and i think your waterpump/flowing coolant through the entire engine is something you want. Air can accumulate even if you didn't do much to the system at all, just bubbles that got moved around (think of a cave with a pond in it... vs. further down, a cave underwater)... but namely, the area the thermastat works in. When you took the thermastat off... it poured out a [email protected] of coolant. It needs to be submerged to work. In the KA, the thermastat is close to where the bleeder valve is, albeit, lower, but low enough to be a low point right? A curver here, a curve there, in the system and you've got an air pocket that formed when you were pullin parts off and puttin back on with no coolant in them. Hours later, new cuts, newly learned curse-words, when you just pour coolant into your radiator and stop when you see it full...
you're forgetting that there's still a huge air cave in the system, and with the way a waterpump works, it needs constant vacuum.. you get too many air caves in there and the fluid doesn't attach itself to itself ~~the fluid~~ and the water pump does not work... it just cools that one spot by the pump.. the whole engine is now put at risk of meltdown cuz of just a lil air. but it actually takes a bit.. it's just where it ends up staying.

air in your coolant is real bad for hydralics (worse for water pumps)... air in a clutch or brake can be really bad when driving... but it doesn't hurt the components.. just you. ;]
air in water pumps... hurt the system.
the components.. melt.

and unless you've always wanted an engine for a coffee table..
 

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course, i prolly saw the Bleeder port cuz my intake still had the stock sticker w/ japanese next to it.

and when you're playin with your hose it may take a while. i've gone through an entire jug of coolant on a maxima before i was done.

and you might want to bump your car on then off... on then off, instead of turning it on while bleeding. unless you have enough in your funnel. ;]

a lot of cars have these bleed ports on the coolant system. just gotta follow the coolant and find it. it's always a bolt by itself, just a bolt. and it opens the coolant system.

here's another fun way to get the air out. ;]

YouTube - 450SX Burnout
 
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