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Old 12-23-2008, 06:46 AM   #1
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CRX Thermostat Temps - Why the Wide Range?

I noticed last winter that I didn't have enough heat in the CRX to quickly clear all the frost/ice from all the glass. When I did the flush and refill thing I also changed the thermostat. The original was for 172* or so. That's low! I'm used to thermostats being set for around 190-195*. I put a new one in set for 175 or so because I wasn't sure about getting a 190* one.

This year it's been cold and we had an ice storm. What a pain to clear the glass with a low t-stat. I want to put in a 190*, but before I do that, why such a low temp stock t-stat? I noticed there are a wide range of available temps. Are they just for different regions of the country? Is there an important reason to have a low temp in the Civic/CRX?

It sounds like a no-brainer, but that's never stopped me from screwing stuff up...thought I'd ask you guys first.

Thanks.
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Old 12-23-2008, 09:33 AM   #2
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I think the low temp thermostats give a little "safety net" if you live in a hot climate and have AC. If the engine is running hotter (195 thermostat) and you have AC on and you get a coolant leak or a clogged radiator, there's less of a margin between "normal" and boiling/overheating. The 84-87 civic cvcc engines were bad about crushing/blowing the head gasket if they overheated. The other issue is spark knock- it gets worse as the engine gets hotter.

On the other hand, too cool of a thermostat will decrease mpg and slightly decrease oil life.

If I was loaning an older car to someone who didn't know much about cars for the summer and if I knew it needed a thermostat, I'd put the lower temp thermostat in.

I have the 195 degree thermostat (I'm a frequent gauge checker), but my problem is that it takes a long time for the engine to heat up so that the defrost will work. I blame the Honda designers that put the thermostat in the lower rad hose inlet instead of the block outlet to the upper hose. This allows hot coolant to circulate into the top of the rad by convection currents.
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Old 12-23-2008, 11:42 AM   #3
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The CRX engine CAN heat up VERY rapidly. Having a lower-temp thermostat can help since CRXs don't have an audible warning or the like if they start to overheat, and they have a tendency to if not watched and maintained.

This is common for most vehicles - usually 3-5 temps available. The more you know about your vehicle, the more you can do something like this.

Erik is dead on in his comments, btw.
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Old 12-23-2008, 01:31 PM   #4
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Thanks Erik & 101mpg. I read your posts from way back that were informative but not spot on in answering the question I had developed.

My CRX starts getting warm pretty quickly, but takes longer than practically every other car I've owned to start producing the kind of heat that clears ice from windows. With a low temp t-stat, it just ain't happenin'.

I know that some people put colder t-stats in to keep temps low for horsepower, and that some put in hot t-stats for FE. But why such a low (172*) in the CRX? Has anyone had any problems using a 190* t-stat? Did the fan come on too often or create other issues with programming for a cooler 'stat?

I haven't been able to find out via web searchs and thought somebody might have some prior experience.
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Old 12-23-2008, 02:47 PM   #5
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If your CRX cooling fan coolant sensor is the same as my 87 Civic, this sensor is in the bottom of the rad- right next to the lower hose. So it doesn't matter how hot a thermostat you put in it, the fan will only kick on when the coolant entering the engine is above a certain temp.

It makes a lot of sense to do it this way. The only drawback is that a grill block can cause the fan to kick on even if the engine isn't getting hot (because the coolant exiting the radiator is still pretty hot due to lack of airflow).
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Old 12-24-2008, 07:36 AM   #6
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Thank you very much. I appreciate your help.

Merry Christmas and a Happy New Year to you.
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Old 12-24-2008, 04:14 PM   #7
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Sounds like your heater core may have some blockage that slows the transfer of heat or maybe the valve that regulates (rheastat?) coolant to your heater core is not opening all the way.

My crx is similar but not as extreme as yours. My HX is SUPER hot very quickly


As for different temp thermostats. I recently replaced one and they parts store didn't tell me there were different ones available. Not sure which one I woulda picked. On a rig I have with a chevy 350 I went with a 195. You'll notice most modern vehicles run hotter thermostats. As for the crx...I also gotta wonder with you if there is a reason for needing that 170ish temp...maybe a threshold for activating certain computer/thermo/vacu switches..???
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Old 01-07-2009, 07:42 PM   #8
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With being in a colder climate I think I'd go with the hotter thermostat if I knew my cooling system was in good shape. I run a 195* thermostat in my '88 Escort. I have the cooling fan on a toggle switch so I can turn it on and off as needed, but the only time I ever have to turn it on is when I'm in town and get stopped by several stop lights. I don't even worry about turning it on unless the temperature reaches 230*+. I doubt that the hotter thermostat would make much difference in the amount the cooling fan runs since most cars are designed where the cooling fan doesn't come on until about 220-230*.
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Old 01-07-2009, 08:01 PM   #9
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When I bought my 84 CRX in Houston Texas it had a 190 thermostat from the factory. I had it changed to the colder one. The CRX was serial number 1018, made in July 1983. Bought it new. Never had a problem with insufficient heat.

Most of the Hondas I have owned warmed up farly quickly, within a couple of miles.

I would have the heater core reverse flushed to see if you have a partial restriction. Also check to make the heater control valve is working properly. I dont remember if it was vacuum operated or cable operated. It was 25 years ago. If the valve is not working the hoses will not get hot without circulation.

Feel the heater hoses when it is warming up to see if you are getting good circulation. Leave the blower motor off and the hoses should both be fairly hot to the touch. Most people can not hold their hands on a 180 degree hose for more than a few seconds without pain. The heater hoses should warm up before the thermostat opens, which is when the top radiator hose will get hot quickly.

A good test of the cooling system is to feel the top and bottom radiator hoses. The temperature difference should be about 60 degrees in the summer and more in the winter. If the bottom hose is very hot the radiator is not transferring heat well, but that is not your problem.

I have also found that in many cases aftermarket thermostats do not seem to allow engines to warm up as fast as the original equipment thermostat. It may be worth it to put an OE tstat in your car, but that will not affect heating potential once it is warm.

If your core is blocked the heater hoses will not get hot, because the coolant will not circulate properly. Heater hoses are not controlled by the thermostat, so they should get hot before the thermostat even opens.

On cold starts I like to keep the heater off until the engine has a chance to warm up enough to see the temp guage move significantly.

That may not be possible in your case, my car stays in my garage, so I don't have to worry about ice on the windows.

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Old 01-08-2009, 06:22 AM   #10
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I got myself an infrared thermometer from Sears for my birthday. It's proven itself and is great for finding cold drafts around doors and windows, as well as ensuring the coffee is at the correct temp.

I had it out to the CRX two days ago, checking the hoses, etc. I had it warmed up and the heater off so I could check out temps when the fan came on.

The hose at the thermostat housing was at about 195* when the fan came on. The hose to the top of the radiator was at about the same. The fan didn't stay on more than a minute and the temps didn't drop much at all. The t-stat I took out last year was rated at 172*. The one I replaced it with was a little bit more...maybe 175 or 178*. Might have been 180*. I don't recall and if I wrote it down I don't remember where I put it. The repair manual shows the t-stat start opening at 172* and is fully opened at 194*.

The young couple that had the CRX before me lived in Rapid City and traveled a LOT of gravel roads. They also had a large white dog. It took an extreme cleaning to get out all the dog hairs and dust. When I did all the body work and took out all the interior panels there was a huge amount of dust and dog hairs under/behind them all. Also, when I first got it there was evidence of prior mouse habitation coming out of one of the vents. I can't be sure I got it all without taking the dash apart. I'm great at taking things apart but I don't relish the thought of trying to get it all back together without breaking old plastic bits.

In the short run, I still wonder why the optional low-temp t-stat. In the overall view, I think it's possible the heater fins are not giving up as much heat as they might due to a thick layer of dust and hair. Cleaning all that off/out is on my list of things to do, but I think a hotter t-stat is called for more.

Thanks again for your insight(s).
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