My background with Hondas/Acuras
98 integra LS stock - wife's car
95 civic cx with built 240whp/165lb ft engine 95x84mm (built by me - daily driver)
90 civic ef hatch back - single cam - stock.

Thermostats: (please bump if you find it useful)

I have a 98 Integra LS. When I bought the car used, it didn't warm up so I knew that the thermostat was stuck open. I pulled it out and replaced it with a Napa thermostat. On longer drives... (45 min or more) I noticed that the temp would go just over half and then drop down to the normal slightly under 1/2 mark. I also noticed that my heat worked really well... too well. If my hand was close enough to the vent, it was uncomfortable. Finally, I boiled over after a couple of longer drives. I pulled the Napa thermostat out and tested it in water. The thermostat did not begin to open until 187'F. At 210'F it only opened to 4mm (measured and remeasured). The water pump cannot pump the volume needed to keep the car cool when it is only open that far... especially at 210'F. Remember, this is behavior from when the t-stat was new.

Below are the detailed measurements of the NAPA thermostat for 1998 Integra LS for all of you:
210'F - 4mm open
205'F - 4mm open
200'F - 2.75mm open
195'F - .75mm open
190'F - .25mm open
187'F - Fully Closed!!!

In addition to this, the Napa thermostat orifice is about 2-3mm smaller in diameter than the OEM. So not only was it not opening at the right temperatures or to the full amount (8mm), the coolant passthrough orifice is actually quite a bit smaller. Remember, when dealing with circles area is 3.14 x radius^2, which means that the loss in orifice surface area is exponentially greater the smaller the radius/diameter of that circle. Essentially what this means is that I was probably only getting around 1/4-1/3 of the flow that I should have when the Napa t-stat was fully open (4mm).

OEM tolerances are as follows (see attached manual image):
Fully open: above 8mm (mine was opening later and only halfway)!
Starts opening: 169'F-176'F
Fully open: 194'F

The Napa t-stat was a far cry from this... obviously.

I ended up paying the money for OEM because I know it will open at the correct temperature. This is extremely important for a couple of reasons:

1. Your cooling system WILL boil over even with proper Honda coolant in it.
2. Your radiator cap has a plastic support column up the center of it, holding the spring and sealing platform to the upper part of the cap. This plastic, when constantly heated above OEM temperatures, gets brittle and breaks. I found my cap in pieces in the top of my radiator. This will also allow the coolant to boil over easier since it is only under atmospheric pressure when it is not allowed to pressurize due to heat. There are other components that will wear faster at higher temperatures as well. Maintaining the proper temperature is extremely important. The difference in cost between an aftermarket thermostat and the OEM is usually about 15 bucks. Don't skimp here. Buy the OEM - it is a quality unit and does the job correctly.

The OEM t-stat part number for the 1998 integra LS is 19301-PAA-306






Giving it props because it rocks:
If you are looking for an oil pan gasket that actually seals check out www.myhondahabit.com for a non-nitrile oil pan gasket. I'm using it, it rocks. I'm also using their oil pan stud kit and their extended intake manifold studs. All excellent products. Ok, onto the topic at hand...
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good to know because i had a napa stat that i was going to use in my build.

 

For a device which can destroy a multi-hundred-dollar engine if it's defective, I can never fathom why people would try and save $15 by buying aftermarket. Never would I ever install an aftermarket thermostat or rad-cap on any engine I ever work on.

 

That is definitely the message here.

 

People need to think here... Why is aftermarket $15 cheaper? Hint: It has nothing to do with "stealership" markup...

 

 

Try and keep in mind Most autoparts stores have a Low end and a High end version of all the parts thay sell.

napa has about Three thermostats thay sell
one is made by Ballkamp (this is owend and run by Napa Corp and mostly not for Cars and light trucks)
one is made by third party and is made as CHEAP as it can be. (it will have a Smaller pellet for opening the thermostat as well as a weaker sring for closing it)
one is made to exced the oem specs and has a Larger pellet and stiffer sping.

you will also find that the third party company makes the same part for other autoparts stores.

like say accardon they make 90% of the electric motors for cars and also distributors (im not sure what all thay do make but i know for 100% thay make those parts)

you can find accardon sold as Napa, Autozone, O'Reilly Auto Parts and Many others
some times there reboxed for the autoparts store to carry ther name on the box and some times there just a plain old white box with a part number on them.

also Alot of the parts you find in an autoparts store are made by the same company that make them for the dealer.
napa sells both NEW and Reman CV axels and the new ones are lifetime warrenty and made in the saome plant that makes them for HONDA, Kia, Hyundia and most other japan auto makers.

not sure if all napas can but my napa here can get parts from a third party source knowen as ALTROM.
Now altrom buys out parts that were over produced for auto makers of import cars this is nice because i can get OEM honda parts for cheap as most parts from altrom are just white boxed dealer parts.
I ordered a set of rear brake pads from altrom sold as ultra8 brand for $10 VS the Napa Pads at $19 and the box i got them in just had a lable over the Honda DEALER lable that was still on the box.

just to throw this out there I know of about 30 differant brands of batteries sold out there but most are still made by the same company. see link below to see who realy makes your battery
http://jgdarden.com/batteryfaq/batbrand.htm#index

So what i'm saying is if you get the Cheap option when your at the parts store don't get mad when it fails and just because you bought it at napa doesn't mean you will get a better one from a
differant parts store doesn't mean its not still made at the same place

 

That is exactly what happened to my radiator cap. Thanks for the pic. I would have provided one, but I already had thrown it away.

 

^all good information; however, Napa didn't offer me one of 3 thermostats, they just offered me the one i bought which leads me to believe they are more interested in making a sale than the right sale. Additionally, who sells a legitimately bad product just to make a sale? If Napa does this, I'm really not interested in buying anything there. If a product sucks and can cause as much damage as a badly designed and produced t-stat, it should not be shelved for sale. A quality company is in business to make a profit and to provide services and products that are good for the customer. Doing only the first is not excusable. Their t-stat no where meets the OEM specifications, yet is sold for that application (orifice size, opening depth, and opening temperature - all failed to meed OEM specifications). That is bad business practice - the kind that would make it hard for me to sleep at night if I were selling this product in my stores.

 

I do agree but you have to remember that not all parts are tested only a few in a run of thousands is ever tested and if thay meet the specs the whole run is deamed good so to say thay sold you a bad part is a little harsh thay may have no idea it was bad and you may hoave gotten the 1 of say 10 bad ones from the run of t-stats that day

Now i'm not a big fan of Napa as a parts store but i do know most of the people that work at my local one and do tend to get a near Employe price on most of the stuff i buy

 

good read

 

Great research. It's a common thing and highly recommended by all to run a OEM t-stat and rad cap. Somethings aren't for screwing around with. And as you figured out these are a couple of them

 

ive never had a thermostat come back in for being bad

 

Ok. But don't assume they don't go bad based on that. Thermostats go bad all the time. They get stuck open and stuck shut, sometimes they even break mechanically (rarely).

That's great for you though. I hate changing them because it is messy.

 

recently i had one stick shut and burst a hose under my hood, good times, and in my old eg coupe i had my radiator carp break just like that one in the pics, caused my car to over heat and couldnt figure it out at first

 

we sell at least 5 thermostats a week and considering ive only had 1 or 2 come back within the last year, i would trust them on my beater integra. would i put one on my rsx? no simply because oem > *** and that car deserves the best

im not saying they are as good as oem, im just saying this thread makes these aftermarket ones sound like they are the devil

after rereading this, for the price difference i wouldnt even bother going with an aftermarket one. never realized oem ones were so cheap

 

great post it really makes you analyze what you buy.

 

Hmm...I wonder which thermostat I have in my RS. It heats up nice and quick, which RULES in the winter time. I'm lovin that.

Most of the Integras I've owned/driven including a few GSRs and a Type R all take the LONGEST time to heat up. I don't even drive my ITR in the winter....but in the spring/fall, it takes about the entire drive home to warm up with a brand new Honda OEM thermostat and Honda genuine coolant.

My RS is the first non-VTEC integra I've ever owned. Do the non-VTEC ones tend to warm up faster than the VTEC models?

 

hmm, this might explain alot

 

My GSR motor takes forever to warm up too, but my wife's integra (the one this thread is about) doesn't take much time at all. I don't think the warm up time changed at all with the t-stat change. That makes complete sense since they are both blocking flow until they are open.

 

Yeah, I realize this post doesn't really cast a good light on non-OEM t-stats. It's not to say that all non-OEM t-stats are bad, but it does demonstrate that there are non-OEM t-stat manufacturers that don't give a rip about whether the t-stat is actually designed correctly. That is enough for me to steer clear of non-OEM. I don't want to do the job twice if some engineer wasn't willing to do his job correctly when designing the non-OEM part first. BTW, I should note that this t-stat, although problematic from the beginning, did not get pulled out for a couple of years. I'm super **** about how my cars run and I won't put up with one that begins to overheat and then cool itself again because of a poorly designed t-stat. My wife mainly drives it and she works very close to where we live so it barely warms up by the time she gets to work. We don't drive far often (beyond 30-40 min), but when we did, that was when it the temp began to go slightly over middle, after parking the car, I could hear the coolant boiling in the radiator because the coolant had been so hot that it destroyed the radiator cap therefore making the cooling system leak and no longer be under pressure. As we know, coolant at atmospheric pressure will boil, but under pressure, trapped in the cooling system it requires higher temps to boil. Anyway, if the t-stat orifice is smaller, it opens less, and opens later, the manufacturer got the t-stat all wrong from the design table. They were just looking for a part to sell and did not care about the end user. If NAPA carries that kind of crap, how can I trust their parts? It's that simple.

 

Super good read. Thank you for the informative post. I'll definitely be buying OEM next time I do a thermostat....

 

Extremely interesting thread. I am having similar issues. My temp gauge seems normal, just below 1/2, but my oil temp gets up to 220 after sustained 80mph driving, so I know my ECT must be close behind (or ahead). I never really thought it could be the thermostat not allowing enough flow, because it 'seems' to be working as I would expect. I will stop by the acura dealer tomorrow to get a new OEM one and will test the old one afterwards. Thanks for this thread!

 

love your choice of words!

 

This is old thread though. I and my buddies all have negative experiences with non-OEM thermostat. I got my project car(B18C1 swapped) with a blown head gasket. It only overheats if I turn off the heater. After I got head gasket fixed it still overheat once I hit the highway. I changed it with Carques one which change nothing. The water inlet hose was COLD even when overheating. Then I got OEM thermostat in 32 bucks, it fixed the problem. I even suspect the bad thermostat was the reason this car head gasket was blown.
The first thermostat has a significantly smaller size of the flowing surface. The second thermostat needs to be tested.