thermostat choice

[SHADY280]

o.k so im driving 1400 miles to msa this year, and back again. i got a 195 thermostat, i think in there right now (heavy modded n/a motor). 3 core dense rad, 16" puller fan. what does everyone else run in hot temps down there. im asking cause my car never sees past 34 deg celcius up here in canada. i just dont want to overheat in cali. really need input on this one. any help is appreciated.

[SHADY280]

im kinda disaapointed in all who have viewed and not answered. there has to be some ppl here that at least know what thermostat they run in there cars. or does everyone have cars that dont run?!?

[JSM]

I'm in Orlando, FL and it gets pretty hot. I run a 160. I'd run either 160 if it was Southern Cali or 180 if it was Northern. To me it is easier to error on the cooler thermostat. But bring a 180 and some tools. Easy swap, unless your housing breaks like mine did.

 

You are driving a NA 240z, 260z, 280z, 280zx?

[Pop N Wood]

When I lived in California some years ago I ran a near stock 2.4L. I had some getting hotter than I liked issues with the stock cooling system when I would go up the mountain to Big Bear lake on a hot desert day.

 

I then puta 3 row core into the stock radiator, oil cooler, chin pan and MSA fan shroud for the mechanical fan. Never had an issue after that. My car also had the vents in the middle of the hood.

 

Maybe some so cal guys with a set up closer to yours will chime in.

[Guest 280ZForce]

I run a 180* thermostat, i believe a lot of us out here run a 180*. Plus it's not even that hot down here, it's not summer yet. We've been in the 60-70s F this month so far.

[BRAAP]

In short, if your cooling system is up to par, then you could run the thermostat that your particular set up is “tuned” to and it should work under all conditions, i.e. no need to change it out other than for routine maintenance.

 

FWIW, All my custom engines that leave our shop, (keep in mind that all these engines are built with performance in mind, not mileage and emissions), and as such, I prefer to run the 160 degree Thermostat, and whatever you do when buying a thermostat, don’t skimp on quality. Over the past few years, I have run into NUMEROUS medium quality thermostats that were bad, i.e. either were very inconsistent varying engine temps, stayed open, or didn’t want to open fully. It has been my experience playing with, and performance-tuning engines, with performance as the primary goal, that cold water and hot oil has allowed the engine to run stronger. Smokey Yunick also supports that theory for making power. Take that for its worth.

 

Keep in mind, that if you do change the thermostat to a different heat range, especially if you go to a drastic change, you might want to retune your AFR’s and ignition timing to compensate for the different thermal environment within the combustion chambers. Your target AFR range shouldn't change, but if left untuned, the actual AFRs will be different, at least slightly.

 

Hope that helps,

Paul Ruschman

[SHADY280]

thank you guys, now i have some info to run off of. i live in canada, so cali is known to be hot all the time according to us whom dont visit down there, esecially in 27 year old cars. i run a heavily modded 79 280zx. the reason i ask is the rad shop that re-cored my rad (3 core dense) said that if i run too cool a thermostat, it will flow too quickly thru the rad, thus not cooling it, but his knowledge is based on our cooler temps. that is why i come here and ask, you guys live down there, drive down there. just made sense to me, sorry i got kinda testy, watching the views go up with no response get to ones brain!!

[Pop N Wood]

...that if i run too cool a thermostat, it will flow too quickly thru the rad, thus not cooling it, ...

 

That statement is misleading to the point of being untrue. It is true the temperature of the coolant may not drop as much in a single pass through the radiator. But you will be moving the coolant faster through the SYSTEM, getting more passes through the radiator and thus should see lower temperatures coming out of the engine. Moving the water faster, within limits, will remove more heat making your ENGINE run cooler.

[Tony D]

I have to agree with Pop N Wood, the radiator guy may be a fine soldering technican but he has a long was to go to understanding what actually happens inside the engine's cooling system!

 

I run a 160 thermostat for a number of reasons. Braap hit manyn of them on the head. But from an underhood analysis of engine components using surface contact probes, thermocouples, and I-R non-contact thermo guns, I came to a realization that in 110 F heat in the desert, the 160 degree thermostat keeps EVERYTHING under the hood cooler!

 

Running a 195 thermostat, on an 85 degree day would result in some underhood components like the fuel rail (75 EFI engine) to run well over 160 degrees. Many of the components nearby the block were also considerably hotter. Switching to the 160 degree thermostat would cool formerly searing components to something that is cool enough to touch with a bare hand! (Less than 140)

 

I have see similar reductions on Carbbed Cars as well. I think the reason the vapor lock problem subsized on my 240 was because the underhood radiated heat load was so much lower and the fuel was not baked as much.

 

I run the 160 on stock radiators, three cores, and four cores all with similar results. I'm in a rush now, so can't detail a lot of the testing, but I change my thermostats twice. Once when summer comes to 160, and on the car that takes short trips, to 180 in the winter. If it is my 'highway car' I run 160 year round down in SoCal.

 

Overall, the temperature of the stock EFI cold-start system usually is satisfied (170-175F) by running the 160. Remember it only starts opening at 160, it is not FULLY opened allowing flow until at LEAST 10F higher! Litte known fact...and confirmed by my underhood temp chasing.

 

Be forewarned, in desert driving on a clear day there are not a lot of aerosols to block UV, I have seen 160 degree thermal layers (the air that actually passes through the radiator) on top of the Macadam surface of the roadways on as little as an 85 degree day! In comparison, in Iowa with heavy aerosols blocking UV, I have recorded 110 F thermal layers on I80 on a 103 Ambient day!

 

The reaction of the radiator to the temperature of the air passing through it can not be discounted. If you are overheating up north, you will play hell down south where the actual cooling air is schorchingly hot! And thermostats will only help somewhat. Make sure it all is in good condition, or slow it down so imparted heatload is less.

 

My car runs cooler at 65mph than it does at 55! Odd, huh?

[SHADY280]

this is why i post questions here, they usually have scientific facts to back them up. i will switch to the 160, and see what happens. my system is in VERY good shape, so no worries there. and since the swap from 180 to 195, i have noticed considerable power loss and engine bay temps come to think of it. ive been trying to tune around it, but hot engines just dont work that way. now would a oil cooler be of any benifit to a car that has NO turbo to severly increase the oil temps?

[Tony D]

i have noticed considerable power loss

 

That's odd, usually when they are on the edge of 'too cold' they will kick in the cold start system and the richening helps on the top end.

 

There may be other forces at work unrelated to the thermostat.

[GeeZ]

Where did you guys get a 160 deg. thermostat? I could only find a 180 at the usual places (Autozone, Oreilly's, Advance). The turbo got so hot that the paint bubbled.

[cygnusx1]

Where did you guys get a 160 deg. thermostat? I could only find a 180 at the usual places (Autozone, Oreilly's, Advance). The turbo got so hot that the paint bubbled.

 

I am about to replace mine also. I might go with a 160 too. Any sources?

 

I found a Wahler Thermostat that rates 160F

 

http://www.autopartsauthority.com/parts_catalog/buy.php?make_text=nissan&model_text=280z&ml=280-z-001&year=1976&part_name=thermostat&brand_name=wahler&r=1&make_code=NI

[z-ya]

Running a cooler thermostat is not necessarily going to make it run cooler. If your cooling system does not have the heat dissipating ability to maintain a 160 degree temperature, then the thermostat will always stay open. Let's say your cooling system has enough capacity to keep your engine at 175 on a hot summer day. If you put a 160 thermostat in, it will never actually reach 160. The engine temperature will continuously vary. I would rather have it run at a consistent temperature. A 180 thermostat in this example would do that.

 

I know we could have a huge debate about this but I have seen how running a hotter thermostat stopped an overheating problem a couple times.

 

In the race car, on my first track session after putting the supercharger on, it overheated and eventually blew the head gasket. When it hit 240 deg, the gasket blew. I was running a 160 thermostat. Got the whole thing back together, and put a 195 in there. The next time at the track, it maintained a constant 195 degrees and did not overheat. The ambient temperatures on the two track days was about the same. No other changes were made (besides a new head gasket). The only explanation I have is that when the thermostat closes, it stops the flow, allowing the majority of the coolant to remain in the radiator longer. It has not overheated since, and has run track sessions in 50 to 95 degree ambient temps.

 

I got the idea to up the thermostat temp from a life-long mechanic that I have a great deal of respect for. He had the same problem in his 429 powered Cobra replica (scratch built). It would overheat with a 180, but not with a 195. He has seen this behavior a bunch of times.

 

I don't think everyone should run out an put 160 thermostats in their cars. If you are not having any problems, leave it alone.

[cygnusx1]

My Z had been running 30- 50 degrees too cold when driven easy and then peaks at the thermostat temperature when driven hard. I suspect that my thermostat hangs open. Since it never overheats, I say the cooling system has not reached its limit. Therefore, a lower thermostat temp MIGHT allow me some ping leeway.

 

Z-YA, I see what you mean about fluctuating temperatures if the t-stat is too low. Basically if the t-stat is wide open, you might as well not even have one in there. If you imagine it's not there (wide open), engine temp will be proportional only to engine load and system cooling efficiency. Both of which will fluctuate causing the coolant temp to fluctuate as well.

[SHADY280]

ive only noticed high under hood temps, and power loss since installing the 195, the engine bay is very warm now. it used to bearable. i think i shall visit nissan and get a 180 or 185, the 10/15 deg. should make a diff. it would also help if i remembered what exactly what i put in, i kept swapping them trying to see what would happen. the last one i remember installing is the 195, so hope im right. i have noticed this cheap stat sticking once in a while, so its best to get a oem replacement. or what other good quality ones can a person get?

[Zmanco]

One other thing to consider: the size of the hole in the thermostat varies by brand. I had a Stant and later put a Nissan unit in (both were 180). The Stant had a significantly smaller opening than the Nissan. I was pretty surprised - I just figured that all thermostats would have the same size opening.

[Slow_Old_Car]

and outside of warmup time... what was the functional reason behind a thermostat?

 

perhaps this is the southern hot states mind set, but down here... i don't see a time where we'd find ourselves driving in 32f or lower weather. and we spend a majority of the year above 80 degrees. in addition to the thermal layer notations by tony c which can have some extreamly high effects too.

 

seems to me if you live in a hot climate, and don't mind the warm up time, that you could run without a thermostat and make the most of the constant cooling rather than stop and go.

 

that being said, i have a 160 unit in my car, and was idling at 179 or so last night with ambient temps being in the 60's.

[Zmanco]

A thermostat enables the engine to operate at a consistent temp regardless of the ambient temperature.

 

It also helps it warm up faster, but for a modern engine (certainly one running FI), I suspect that is a secondary benefit.

[Pop N Wood]

Fuel injected motors are sensitive to the thermostat used

 

From this thread

 

Well, the newest news is that I failed emissions again! The idle hc reading was almost 4 times the limit (875ppm to a limit of 250ppm). I called the tuner to see if they had missed something, but his records showed every trim was spot on. So.... I went to an emissions specialist place today and really got schooled on LS1 engines. Turns out that all the stuff I've done to make the engine run cool are really problems. They said to reconnect my MAF water jacket, and to loose my 160 degree t-stat and put the stock 180 degree unit back in. The engine was flipping between open loop and closed loop operation because it couldn't tell how hot it really was, and open loop equals very rich. They also said my intake air sensor was bad, adding to the temp problem. AND the biggest fubar was that the shop who reflashed my computer last year was supposed to turn the back two O2 sensors off, but they didn't. So now the front sensors are reading at one end of the scale, and the rears are at the other extreme because there's nothing plugged in to them. Again the computer is confused on what to do, so it dumps in more fuel. Oh, and the two O2 sensors that are on the car are slow responding and should be replaced. So now I need an IAT sensor, new O2's and simms. Another $500 or so to piss away. I sure hope all this works, cause I'm about out of options and patience (not to mention money!)....