Howdy all -- my first post here to the forum, after my obligatory intro post.

This '98 Civic EX is my daughter's -- she bought it this past November, so we're still getting used to it. I happened to be out in it today when I noticed the temp gauge was reading rather high. I had the A/C on, so I shut it off, but the temp continued to climb. Pulled over at a service station and noticed that the top radiator hose had blown, and there was about a 2-inch long rip in it. Fortunately, this service station was next door to a drug store, where I was able to buy a roll of duct tape, which was good enough to get me home.

I noticed when I was first filling the radiator that the fan wasn't spinning. The car had managed to lose most of its coolant and I was wondering if it has the sort of temp sensor that requires being immersed in coolant in order to operate properly. If it would have come uncovered, I reasoned, then perhaps this was why the fan wasn't operating. I was also wondering if the non-operating fan may have led to the hose's failure, cuz it still looked to be in good shape at least. Except for that nasty separation.

Well, replaced the hose and added coolant (I had my daughter replace the hose, btw -- something she shouldn't be afraid of doing), then fired up the car and waited for the temp gauge's needle to reach mid-scale. Still, the fan wasn't running. I had her turn on the A/C, thinking surely it would kick on the fan then, but still nothing. Oh, and the fan spins freely -- it doesn't have a frozen or stiff bearing or anything.

Weather's been from cold to cool since she bought her car, but now things are starting to warm up here in Houston, and when she might have been able to get away with a non-operating fan in the cold months, that isn't gonna be the case any more.

So, my questions are, first of all, what are the normal operating parameters for this car's cooling fan? E.g., when should I typically expect it to switch on? Does the fan automatically switch on when the A/C compressor is engaged?

Next, since I'm likely gonna have to troubleshoot things, I'd like to know where a good place to start is. I've already done the obvious and checked the fuses. I don't know where the temperature sensor and/or fan controller(s) are located on this motor -- or cooling system. If you can advise on a good way to proceed in this regard,I'd appreciate it.

Since I will likely be the one doing most of the maintenance on this car, I'd also appreciate any input into which are the better repair manuals to use. For years, I've used a Haynes manual for my Volvos, and back in the old days when I drove a Civic with a CVCC engine, I had John Muir's incredible guide to use. I know that there are often lots of things offered on CD/DVD now, but my experience with this type of product so far has been much less than favorable. That is, they were junk for the most part, and pretty much useless. I'm old school enough, anyway, to prefer good old paper -- even if it does get all smudged up with dirt and grease. All part of the process.

 

The fan is started by the temperature of the coolant leaving the radiator. It takes quite a while idling before it will start. If there is no flow through the radiator, it won't start.

The A/C is entirely separate. The condenser fan only cools the condenser.

 

You can download the service manual from here - hondatech.info: Honda service manuals it is rather large (38MB) but well worth it.

The fan is controlled by a thermistor assembly (Engine Coolant Temperature Switch - ECT - PAge 10-10 of the service manual) that screws into the thermostat housing - it does go bad... if your fan does not kick on after 15 minutes of idling then it is more than likely bad. You can always replace it for good measure as they are fairly cheap and known to go bad.

To test the fan, find the relay in the under-hood fuse/relay box (the manual for the layout starts on 23-52) and pull it, and jumper the contact points in the box where the relay would be. The fan should immediately turn on... if my memory serves me right, I think it will run with the key off (when jumpered).

Hope this helps, and good luck.

 

Thanks for your reply. I waited until the upper radiator hose was hot, signifying to me flow from the engine to the radiator. I'm gonna assume the radiator isn't clogged at this point. Wasn't aware of the condenser fan. I'll give it a look anyway and make sure it's operating also.

Thanks for the link and the advice. I'll d/l the manual and have a look-see. I'll report back and let y'all know what I've found out.

 

My apologies if you covered this already, I simply read what Mk said (you quoted) and your reply to that.

Coolant travels through the motor, then through the upper hose, radiator, lower hose, tstat, then back into the motor. The upper hose will always get hot regardless since the coolant is coming from the motor.

If the lower hose gets warm, you can tell that the radiator is not 100% clogged at that point. Also, if the lower hose gets warm, that also shows that the Tstat should be working properly.

 

Okay, you got me, I suppose. I was assuming -- wrongly I guess? -- that the t-stat was located under the water outlet on the cylinder head. That's where they've been located on every car I've owned. Er, well, I don't recall off-hand where it was located on my old CVCC Honda, but I suspect I would remember if it would have been located down under. So, according to your verbal diagram then, the T-stat is located downstream of the lower hose, correct?

I mention all this because that's the way I've always checked if the thermostat opened up -- by feeling the temp of the upper hose.

Anyway, I'm happy to report that my fan appears to be working normally. Took about 20 minutes at idle before the fan finally kicked on, but that's fine. I took a look at the temp gauge and it was still reading dead-on in the mid-range. Dunno about Honda, but Volvo has a significant -- um, dunno what it's called -- a damping circuit maybe? -- that has the effect of the temp needle staying right in the middle of the range until the cooling system is almost catastophically hot, then finally it will begin swinging up into the "H" zone. Just wondering if Honda does something similar. I tend not to think so, though, based on the way the gauge was responding yesterday -- or at least it isn't damped as heavily as Volvo's is.

 

Glad you got this figured out.

I have been having a very peculiar problem that I think I have fixed. Last summer I blew a heater hose - coolant went everywhere. I had the car towed home, replaced the hose and while I was at it, replaced the timing belt, all belts, water pump, motor mounts, cam shaft seal, thermostat, and a slew of other stuff...

I filled it back up with coolant per the manual and it runs fine, but was still losing coolant. It was overflowing/puking from the overflow container. I was adding about a quart of coolant every 2 - 3 weeks.

After months of messing with it, I thought it was a head gasket problem, and started to get worried...

I read somewhere that when you add coolant to these things, follow the manual - but take it a step further to ensure you elevate the front end (jack it up, park on an incline) and fill the cooling system per the manual. The concept makes sense because when the thermostat opens and you have the heat lever all the way to the right to ensure fluid is flowing through every nook and cranny, the elevated radiator ensures any bubbles travel up and out.

I did this as a last resort, and ensured the overflow bottle was not too full.

It has been 2 days and so far, no coolant overflow whatsoever.