Underheating problem? lol

[DataXUnknown]

Recently my car is running kinda funky. Like performance wise it's pretty normal. It's an S13 hatch with a blacktop SR20DET

-z32 fuel filter
-walbro 255lph fuel pump
-hks intake (fucking huge filter)
-3" exhaust piping all the way turbo back
-apexi dual chamber bov
-bee*r rev limiter
-hks turbo timer

And here I state the problem. My exhaust is like blowing AC or something lol. My exhaust temp is so normal air temp that I can stick my hand inside my pipe (fisting my exhaust oh yeah baby), and touch the exhaust with no problem. It kinda makes a very faint noise too like something maybe is loose.

Also my temperature gauge on my cluster goes down when I step on the gas depending on how much I push the pedal the farther it goes down.

This is all when my car is warmed up too. It's also (judging by the smell and 12mpg) running rich as fuck.

I have an oil pressure gauge and everything seems pretty normal. Oil pressure goes up to like 80psi at full throttle, 10-20psi on idle.

[haggard240]

lol i never heard of anything like that even after you drive for a while the exhuast is still cold??

[DataXUnknown]

Could my radiator be too big? I have a mishimoto 3" core I think it is. I put a lot of antifreeze in it and bled it for a long time because i know how sr's are notorious for overheating...never thought i'd come across this problem though.

so weird how the temp needle is going down when i hit the gas. the thermostat is fairly new (little less than a year old). could the water pump be pumping too much or somthin? is that even possible?

n yea exhaust is still cold. im gunna push it pretty hard tonight i'll let you know if it gets any hotter. (throwin flames off the limiter im sure will heat it up)

[GSXRJJordan]

Stock temp gauge sucks - get a real temp gauge.

Sounds like you have a leak that lets cool air into the pipe as the exhaust passes through, cooling it down. Without an EGT gauge, you can't tell how "hot" or "cold" the exhaust actually is.

[aNskY]

running rich will keep your exhaust temps (and power) down

try getting a fpr to lower the increase in pressure from the 255lph pump


altho i used to run no fpr on a walbro/stock turbo and i was nowhere near 12mpg.. more like 27-28

[NMs14.5kouki]

i have the same problem until i go really hard on my car, daily driving, the temp stays 10 celsius below operating temp, its strange, my setup is not like yours at all tho. what thermostat you running?

[d-magic]

the problem seems like you have a bad thermostat, like it's stuck open. Basically, If your car is not at operating temperature, the car will run rich until you go into closed loop. The thermostat should stay closed until operating temp is achieved.

[Banegraphix]

Unless your running 550cc or higher injectors on a stock SR ecu I really don't see how your getting that bad of gas milage. I would get a EGT gauge and wideband to see whats going on, I run the same radiator and in normal driving in Florida heat It stays around 180

[silviaz]

I had the same problem as u.

I changed my water temp sensor. The connector was also loose, that's why when you pump the gaz, the temp. lower.

[DataXUnknown]

The temp sensor is pretty new, less than a year old. I'll check to see if it's loose though.

Thermostat was pretty much replaced at the same time my temp sensor was. It was just a normal OEM one from westco nissan. I was thinking the thermostat was stuck open too, but I know people that run no thermostat at all (open all the time) and it's perfectly fine.

FPR is my next "to buy" item just gotta gather some $ for it. As well as a new water temp gauge.

[artdrifter]

yeah i thouhgt i had that problem until i looked and the wire was disconnected. lame

[d-magic]

i thought you said your engine is blowing cold exhaust? I don't know how running an open thermostat at all times is good. It's better than being closed, definetly. That can explain your low mileage too.

[S14DB]

low egt is usually running rich.

[jspeedm]

The temp sensor is pretty new, less than a year old. I'll check to see if it's loose though.

Thermostat was pretty much replaced at the same time my temp sensor was. It was just a normal OEM one from westco nissan. I was thinking the thermostat was stuck open too, but I know people that run no thermostat at all (open all the time) and it's perfectly fine.

FPR is my next "to buy" item just gotta gather some $ for it. As well as a new water temp gauge.

running with no tstat will actually overheat your engine. check for an exhaust leak first. do you have an 02 sensor or wideband? if you have an exhaust leak before the sensor, the computer will dump fuel into the engine to compensate for the extra air. the cooler air entering the exhaust combined with the extra rich mixture could make the gasses coming out the tail pipe seem cool.

[ixfxi]

running with no tstat will actually overheat your engine

oh really..................


what planet do you live on?

[jspeedm]

oh really..................


what planet do you live on?
the planet where coolant moving through the engine too fast wont absorb the heat from the cylinders efficiently. your coolant temp will be low but that's only because it's not doing it's job. cylinder temps will be higher.

it's called thermal physics.

[ixfxi]

the planet where coolant moving through the engine too fast wont absorb the heat from the cylinders efficiently. your coolant temp will be low but that's only because it's not doing it's job. cylinder temps will be higher.

it's called thermal physics.

you're contradicting yourself. how can your coolant temp be low and simultaneously overheat the engine.

the only downside to running too cold is that you will be out of the motor's efficiency-range and that it will take longer for the oil to warm up.

thermostats didnt always exist and motors continue to work the same way they did 100 years ago. there were engines that had thermosyphon or air cooling, remember?

dont forget, a water pumps flow is not consistent and dependent on RPM. but you already know that.

[GSXRJJordan]

Its rumored that if you pass the water through the engine and radiator too fast, you won't have enough time to heat the water and cool it off... so in that since Mike, it's not a contradiction...

...but I haven't seen any evidence of this ever happening in a street (production) motor. That certainly isn't the problem here. Everything else Mike noted is true though, the motor (and the air passing through it) being out of it's efficiency range (which is about 190* for SR20's) and the oil not being up to temp are your biggest problems.

[luftrofl]

Its rumored that if you pass the water through the engine and radiator too fast, you won't have enough time to heat the water and cool it off... so in that since Mike, it's not a contradiction...

If that logic were true (not just rumored) then it wouldn't be a contradiction.

the planet where coolant moving through the engine too fast wont absorb the heat from the cylinders efficiently. your coolant temp will be low but that's only because it's not doing it's job. cylinder temps will be higher.

it's called thermal physics.

So you failed thermodynamics?

The idea that you don't have enough "time" to heat up the water is ridiculous. A higher flow rate will keep the engine cooler because the coolant will stay at a lower temperature so it will absorb heat faster and thus the cooling system will be more efficient.

Regardless, the point is moot as the primary purpose of opening the thermostat is to keep the coolant at a relatively low temperature, when the engine reaches operating temperature- the change in flow rate is not significant.

[FrankDukes]

running with no tstat will actually overheat your engine. check for an exhaust leak first. do you have an 02 sensor or wideband? if you have an exhaust leak before the sensor, the computer will dump fuel into the engine to compensate for the extra air. the cooler air entering the exhaust combined with the extra rich mixture could make the gasses coming out the tail pipe seem cool.


Your thermostat is meant to heat up your engine, then open and circullate the coolant when it becomes hot enough.

Running with no Tstat will actually mess up your Engine and not Overheat it.

Running with no Tstat will probably damage your engine block. If your car sits outside in the cold weather and you wake up in the morning and try to warm it up, it will take about 20 minutes to do so. You have an open thermostat/no Thermostat that allows all the fluids to circulate. It makes your engine work a longer time to warm up all that fluid from your Engine, Intake, as well as the radiator.

In the case that your thermostate does not open, then it will mess up your engine because it can't cool properly. The main function of the Tstat is to help your Block get warmed up before you drive it.

It is like you should not turn of the Heater in the morning, because the coolant will bypass and go through your Core and takes a longer time to warm up. It is the same reason why if you are overheating you should turn on your Heater with the windows down (in C.A.) so more fluid is circulated and thus cool your engine.

Answer to OP's Problem:

BLeh, it's not an issue at all. It is due to Electrical issue with the sensor. When I have my aluminum coolant resevoir too high filled with coolant, this problem occurs, because due to gravity, the radiator cap cannot push the hot coolant out and it fluctuates up and down. When the coolant level is perfect, the problem doesn't occur and the temp gauge stays still.

On occasions the gauge will hop up and down as I accelerate quickly, that is just because when you accelerate your Water pump is spinning faster and the flow may not be consistent due to various belt tention issues. I think that my belts are warn out and sometimes it will catch well and sometimes it slips while accelerating, thus the water pump and the temp gauge fluctuates.

Temp Sensor may be an issue or broken, being that our cars are OLD!! I've had to Solder about 5 different electrical pigtails on my 240 this year, so I wouldn't be suprised at all due to the age of the car.

But, since it is not overheating, that is good, It ain't broken and doesn't cause any problems so I stick by my rule "If it ain't broke, don't break it!"

In addition, a Few air bubbles may just be stuck in there and just Messing with you. =) I use the bleeder screw every once in a while to check/release Z bubbles.

[Row]

Running with no Tstat will actually mess up your Engine and not Overheat it.




running an engine without a thermostat will overheat and mess up the engine. as the coolant circulates through out the system , it keeps heating up and doesn't have time to sit in the radiator to cool down.

[Razi]

I'm sure people run with no themostats on their tracked 240sx's with no overheating problems.

[S14DB]

running an engine without a thermostat will overheat and mess up the engine. as the coolant circulates through out the system , it keeps heating up and doesn't have time to sit in the radiator to cool down.

These aren't SBC's...

[ixfxi]

running an engine without a thermostat will overheat and mess up the engine. as the coolant circulates through out the system , it keeps heating up and doesn't have time to sit in the radiator to cool down.

gaddamn another one.

ive never read such misinformation. if you guys have facts, actual proof, then post it. i dont want to hear this nonsense about the coolant not having enough *time* to absorb the heat. You guys make it sound like a relationship, there is a time that the coolant needs to sit down, have coffee, chit-chat and get to know the engine block... then when ready, the block gives the coolant some heat. How sweet.

I mean what you guys dont understand is that the water pump does not flow consistently (as it is variable) and that there is resistance in the system. Flowing through a radiator is different than water flowing through an empty pipe.

[Row]

gaddamn another one.

ive never read such misinformation. if you guys have facts, actual proof, then post it. i dont want to hear this nonsense about the coolant not having enough *time* to absorb the heat. You guys make it sound like a relationship, there is a time that the coolant needs to sit down, have coffee, chit-chat and get to know the engine block... then when ready, the block gives the coolant some heat. How sweet.

I mean what you guys dont understand is that the water pump does not flow consistently (as it is variable) and that there is resistance in the system. Flowing through a radiator is different than water flowing through an empty pipe.

whatevers man. I'm an auto technician, and i deal with cars every week. sorry that I'm not one of those that says "get that thermostat out of my engine , I don't need it anyways".

[brent the junkie]

I ran my old s14 hard everyday for 2 years without a thermostat and I never had a problem with the car and it was always in a good mood lol. Only reason I stopped was cause I was forced too. Totalled the car out :(

[jspeedm]

gaddamn another one.

ive never read such misinformation. if you guys have facts, actual proof, then post it. i dont want to hear this nonsense about the coolant not having enough *time* to absorb the heat. You guys make it sound like a relationship, there is a time that the coolant needs to sit down, have coffee, chit-chat and get to know the engine block... then when ready, the block gives the coolant some heat. How sweet.

I mean what you guys dont understand is that the water pump does not flow consistently (as it is variable) and that there is resistance in the system. Flowing through a radiator is different than water flowing through an empty pipe.

sorry to tell you, but heat does not transfer instantaniously.

whatevers man. I'm an auto technician, and i deal with cars every week. sorry that I'm not one of those that says "get that thermostat out of my engine , I don't need it anyways".

i am a certified master tech, and i agree.

I ran my old s14 hard everyday for 2 years without a thermostat and I never had a problem with the car and it was always in a good mood lol. Only reason I stopped was cause I was forced too. Totalled the car out :(

2 years is not a long time. i drove my first s14 for 7 years and my current one for 3.5. i am not saying that it is going to instantly kill your motor, but, a motor with a tstat will last longer than one without under the same driving conditions.

[DataXUnknown]

I know this isn't too related to my underheating problem, but from my running to rich problem. Recently I visited my buddys car at a cool JDM shop and the guys were saying his injectors were bad, they were constantly pumping too much gas in, but everything was ok when the engine was being pushed because there was more air coming in.

So could my injectors be pumping to much gas in? They are stock and I have had problems with them before, but then just ran injector cleaner through them and it fixed the problem. Or could I simply just need to clean/replace my filter?

[s13boy89]

what about cts

[DataXUnknown]

mario did you even read through the thread? lol the cts was replaced less than a year ago and is tightened on there nothing loose or anything.

[s13boy89]

nah i just posted

[s13boy89]

what if you get a safc and lean out your injectors a little

[DataXUnknown]

^that was an option I was keeping open if i get the money.

[luftrofl]

sorry to tell you, but heat does not transfer instantaniously.

You are mistaken. Heat does transfer instantaneously- it will transfer just as quickly to a flowing fluid as it will to a stationary or slower-flowing fluid, provided that the difference in temperature is the same in all cases.

[Codrifter]

ixfxi actually your wrong go talk to any skilled tech not your local shop tech. and he will tell you what were telling you now im not saying that it will overheat your engine but it can cause higher normal temps cause its not giving the coolant enough time to absorb heat. and for the last post heat does not transfer istantaneously it need time how ever it being milliseconds it still needs time as it passes by the cyclinder walls. now that may not be the same for every car depending on how clean the water jacket is and how thin the cyclinder walls are and so on. but to the original problem if your engine is dumping fuel it will wash down the cyclinder walls causing the cyclinder temp to be low which could cause there to be low engine temps cause theres not enough heat coming from the cyclinder to heat up the coolant and it also depends on what your running through the engine like straight water or 50/50. and that would account for the shit gas milage cause your just dumping excess fuel into the exhaust that wasnt burned in combustion. and that would also account for the low exhaust temps also but if your running that pig rich there should be some black smoke. but there is many thing that could cause this like you car never goes into closed loop and always stay in open loop that causes the computer to just want to dump extra fuel to keep it running. is there any type of hesitation when you snap the throttle.

[luftrofl]

its not giving the coolant enough time to absorb heat. and for the last post heat does not transfer istantaneously it need time how ever it being milliseconds it still needs time as it passes by the cyclinder walls. now that may not be the same for every car depending on how clean the water jacket is and how thin the cyclinder walls are and so on. but to the original problem if your engine is dumping fuel it will wash down the cyclinder walls causing the cyclinder temp to be low which could cause there to be low engine temps cause theres not enough heat coming from the cyclinder to heat up the coolant

Okay, so prove it. I have no idea where you're getting the idea that less heat transfers because the coolant is flowing.

As long as there's contact between the fluid and the surface, you're going to get heat transfer- it doesn't matter if the fluid is moving or not.

[DataXUnknown]

*goes to check antifreeze* i used 50/50 and bled the shit out of it. so my car is simply just running too cold? how do i make it warmer hahaha. take some coolant out?

or is my radiator simply just too big? its a mishimoto i think it's a 3" core if i remember correctly.

[GSXRJJordan]

You don't even know that it IS running cold, Wes. Get a real temp gauge.

[DataXUnknown]

^Yes sir!

lol thanks jeff. pickin that up tommorow.

[Codrifter]

what degree thermostat are you running that could be you problem to cold and you car will never warm up sorry if you already said. and i never said that you dont get any heat transfer but you don't get enough so read before you speak. and if you knew anything about an engine than you wouldn't be talking. besides in your case being a red neck back yard mechanic that doesn't know anything doesn't qualify you to be giving someone advice.

[luftrofl]

what degree thermostat are you running that could be you problem to cold and you car will never warm up sorry if you already said. and i never said that you dont get any heat transfer but you don't get enough so read before you speak. and if you knew anything about an engine than you wouldn't be talking. besides in your case being a red neck back yard mechanic that doesn't know anything doesn't qualify you to be giving someone advice.

Take a moment please to learn what you're talking about.

If you knew anything about fluid dynamics, you'd know that the velocity of the fluid is effectively zero at the edges of a pipe so saying that the fluid is going too fast for the heat to transfer is false.

Fluid velocity in a pipe is proportional to the radius squared minus the distance from the center squared: v ~= (radius^2) - (distance^2).

(Hagen-Poiseuille equation)
http://img7.imageshack.us/img7/8697/240db86cc22ef6626ae50bb.png

[FrankDukes]

running an engine without a thermostat will overheat and mess up the engine. as the coolant circulates through out the system , it keeps heating up and doesn't have time to sit in the radiator to cool down.

I would respectfully disagree. According to technical definitions:

While the thermostat is closed, with the exception of the small bypass flow, all of the coolant flow is recirculated to the engine without being cooled in the radiator as the engine warms up. The thermostat stays closed until the coolant temperature reaches the nominal thermostat opening temperature. The thermostat then progressively opens as the coolant temperature increases to the optimum operating temperature, reducing the coolant recirculation flow and increasing the coolant flow to the radiator. Once the optimum operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant recirculation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range as engine heat output, vehicle speed and ambient temperature change. If the load on the engine increases, increasing the heat input to the cooling system, or the vehicle speed decreases or air temperature increases, decreasing the radiator heat output, the thermostat will open further to increase the flow of coolant to the radiator, preventing the engine from overheating. If the conditions reverse, the thermostat will reduce its opening to maintain the coolant temperature.

***So, it opens to to cool the engine, if there was no Thermostat (It will be always open) and thus cool underheat the engine.***

In otherwords, The Tstat's purpose is to keep the hot coolant in the engine until the engine block comes up to Optimum temperature. It waits until your block is at the right temperature then it opens to circulate the coolant. In simple terms, It is used to warm up your engine quickly as I've indicated in my first post. It will close to warm up the engine and not allow the coolant from the Radiator to circulate inside the engine block. So, in theory and from experience, running with NO Thermostat will definitely NOT OVERHEAT, BUT UNDERHEAT Your car. Yes, it will not run at optimal temperature, but the argument you have given is incorrect.
The thermostat's purpose is to regulate the temperature at an EQUILIBRIUM, an ideal temperature so the car performs as OEM / STOCK specifications and optimum purpose.


I'm sure people run with no themostats on their tracked 240sx's with no overheating problems.

Yes, they do. Many people do. One way you can tell is hooking up a water temperature gauge on your car with a Thermostat and doing it without a thermostat. I've done so and my coolant temperature is significantly lower without a Tstat. Those who have never done the measurement, you're talking without any logical support to your premise. :duh:

I ran my old s14 hard everyday for 2 years without a thermostat and I never had a problem with the car and it was always in a good mood lol. Only reason I stopped was cause I was forced too. Totalled the car out :(

Yes, I've driven many cars without thermostats in my life. Never had an "OVERHEATING" issue which many "Mechanics" and "ASE Mater mechanics" on here argue about.

I studied 4 year related courses on Fluid Power, Dynamics as well as heat transfers of materials.

[FrankDukes]

Just go here and CLICK PLAY!:

http://auto.howstuffworks.com/cooling-system2.htm

[Bigsyke]

Zilvia is funny shit. 4 year courses at 15yrs old.....suddenly when aerodynamics or cooling comes up, at least 5 people pop off and claim they are scientists. ive heard some "skilled" techs say some of the dumbest shit, and have strictly book smarts, which should not apply to tracked vehicles.

If heat transfered right away with 50/50 why do we need water wetter then? Either way, run a fucking thermostat.

OP an OE radiator is actually superior to the mishimoto in cooling terms.

[FrankDukes]

Zilvia is funny shit. 4 year courses at 15yrs old.....suddenly when aerodynamics or cooling comes up, at least 5 people pop off and claim they are scientists. ive heard some "skilled" techs say some of the dumbest shit, and have strictly book smarts, which should not apply to tracked vehicles.

If heat transfered right away with 50/50 why do we need water wetter then? Either way, run a fucking thermostat.

OP an OE radiator is actually superior to the mishimoto in cooling terms.


I never use my real name or age online. I am over the 1/4 of a century years of age. =)

I've heard an ASE guy at EZ/Jiffylube, said that "If you don't do a coolant flush your engine will blow up." And didn't get sued for that?

The OP said that his cooling gauge is lower than average and fluctuates at times. I said don't worry about it.

Someone said that "No Tstat will Overheat." so that is why there is this arguement. 50/50 of the peopel say it's correct, and the others say likewise. GETTING WAY OFF TOPIC.

[ixfxi]

ixfxi actually your wrong go talk to any skilled tech not your local shop tech. and he will tell you what were telling you now im not saying that it will overheat your engine but it can cause higher normal temps cause its not giving the coolant enough time to absorb heat.

Okay, so prove it. I have no idea where you're getting the idea that less heat transfers because the coolant is flowing. As long as there's contact between the fluid and the surface, you're going to get heat transfer- it doesn't matter if the fluid is moving or not.

I cant believe this discussion is being debated, let alone still going.

I think the problem here is that certain textbook professionals need to step off their pedestal and need to further their education. Think rationally for a second here, saying that coolant needs time to absorb the heat would be like telling a firefighter to lower the pressure on the hose so that the flame would get doused slower thus making it more effective - its asinine.

The coolant system is not designed as precise as you guys make it out to be, hence the reason temps change and are not consistent. In most conditions, the cooling system works as designed. In harsh conditions, stock may be underdesigned.. this is why we do things like install upgraded radiators and lower temp thermostats.. it all depends on what we're trying to accomplish.

I think the point everyone here is trying to make, isnt whether or not to install a thermostat - because we all know that in pretty much every application a thermostat is necessary.

[luftrofl]

If heat transfered right away with 50/50 why do we need water wetter then?

Water wetter works to prevent air bubbles, which reduce the contact area between coolant and metal, from forming in the cooling system. By maintaining a higher surface area, the overall rate of heat transfer is higher.