Quick Background:
‘98 2.3CL 210K miles (Simular to an Accord)
New rad (old one sprung a leak)
New thermo and all coolant hoses

Car’s been running fine the last few months (that’s when the rad / thermstat and hoses were replaced).

The last few days the car temp is perfect driving around town (and the fans kick in normally) but climbs up to the half way mark on the highway. Slightly higher when going up hills on the highway. Then stays at the half way mark for the ride home through town after getting off the highway. Pull into my driveway and the fans are not on. Shut the car off and the fans kick on…

Fluid levels in the rad and res are normal and there are no obvious leaks. My thought is the thermostat is bad but it was just replaced and the car acts fine in town (before hitting the highway).

Engine seems to idle and run fine.

Any ideas?

 

Lets assume the tstat is stuck open, one purpose of the tstat is to stop the flow of coolant, hold it in the radiator so the ram air and fans can cool it off, it seems yours is stuck open, the coolant is flowing through too fast at highway speeds and is not cooling off very much.

Start it from scratch, and monitor both radiator hoses by hand, they both should not warm up at the same time, this would be a stuck open tstat, common problem with Hondas but even more so with aftermarket parts, get the correct part number from the dealer if you think it is bad.

 

That makes sense!!! I was starching my head all day think what would cause this problem…. It did not make sense that the car would be getting hotter the faster it went….

And yes I the part I got was aftermarket and not Acura OEM.

I'm going to go feel my hoses now and see how they warm up!

 

Well the top hose rad hose was getting hotter before the bottom. Is it possible the tstat is working bust opening too much or too little? Either way I think my next step is to get one from the dealer and replace the aftermarket ASAP…

 

I just took out the tstat and tested it in hot water per the manual. Seems to be working fine.

 

So I checked the Tstat and that was fine (water test on the stove per the service manual) I filled the rad the propper way for the 1st time. Using the bleeder on top of the Tstat housing. Opened the bleeder while filling the rad until coolant came out (per the manual). Went for a ride. Temp is solid and steady!!!! My one theory is air was trapped in my heating core and came out the last few days as it was the 1st time the heater was on this season. My other theory is If I filled the radiator the proper way this would have never happened. Just another example of what you should RTFM!!!

Thanks for listening!

 

OK,, For those of you following this I spoke too soon! The car is still getting hotter on the highway, particularly the hills. Since I ruled out the Tstat and air in the system I’m beginning to think it’s the water pump. I had the timing belt and water pump changed 80K miles ago, but honestly I don’t trust the place that did the work so you never know (could be the original water pump)….

As an experiment I down shifted on the hills to up my RPMs. And guess what,,, the temp did drop down. Making me think the water pump is not working at the required efficiency and the higher RPMs are needed to get enough flow through the rad. Do these water pumps “wear out”. Are the impellers plastic or metal? I was going to replace the timing belt / water pump soon anyway, might have to put a rush on it!

 

You may be very correct in all aspects, I like to put the jug on top of the radiator cap neck and keep an eye on it for bubbles coming out, when it clears up, I like to run it up to about 3000 RPM and watch for more bubbles (big ones) means air still in system, once that clears up at 3000 then any further sign of bubbles is a sign of a bad head gasket. I also like to do an IR temp gun across the radiator looking for cooler spots and this is a sign of a slightly clogged radiator.

As far as a worn water pump, even a brand new one can errode quickly with the wrong type antifreeze installed or electrolysis in the system, a digital volt meter can check for this, one probe to ground and the other dipped in the antifreeze with the engine running fully warmed up.

Air in the heater core mostly means no heat, not overheat the engine (until that air moves into the head), getting air out has proven to be an issue sometimes. Keeping the radiator topped off is assurance that the air is working itself out and having heat is a good sign too.

Your diagnosis should tell us something like you stated, raising the speed of the engine helped but the air running through the radiator is the same so the water pump is suspect but again the inside of the head and engine need to be clean, no brown junk from corrosion or stop leak or head gasket repair in a bottle, is there any build up on the inside of the radiator cap.

 

Bumping this back up with some new findings....

So last night I drove home in stop and go traffic for 45 mins and the gauge never moved from the normal 1/4 - 1/3 mark.

This morning I'm driving with no traffic on the highway and it goes back up to the half way mark. Then I hit traffic and it goes back down. Traffic ends, I speed up to 70 and on cue it creeps back up to 1/2. At least it was acting consistent today.

I get off my exit, pull into Dunkin Donuts right off the exit with the gauge still at 1/2 and the fans are NOT on. They do kick on like normal after letting the car idle for about a minute. But get this... With the car running and still at 1/2 on the gauge I shut the car off and turn on just the ignition. The gauge bounces down to 1/4. Fire up the engine and it goes back to 1/2. Def a strange hot spot or false reading.

My two ideas are:

• Swap out this sensor since its only 30 bucks just to rule it out

• Monitor the ECU to see what temp it’s reading and if it fluctuates like the gauge.

By the way I picked up a no-spill funnel to fill the system and burb out any air:

As seen here:
http://www.troublecodes.net/ar...3.jpg

Thanks again for any insight...


Modified by Nickbee at 1:14 PM 10/12/2007

 

I had this problem, and then the temp gauge started goin in the red. After replacing sensor, tstat, flushing coolant 2x, nothing changed.

the needle would climb to red about 20 sec after starting cold engine.

After flushing coolant 3rd time, I saw that the coolant would start to overflow out of the radiator when I opened the throttle. I am changing the headgasket in a few days to see if that was the problem.

In the mean time, the gauge is burnt out now.

 

SuperSlow,

Sounds like we might both be barking up the same tree. After filling and burping my system two days ago (with the no-spill funnel, it's a great tool), My radiator level is below the filler neck tonight. Also squeezing the top rad hose I can tell it is dry. I don't think that should be the case. I think I'm either leaking or burning coolant. I think my next step is to do a pressure test on the system to see if there is a leak (there is none that is obvious) or give up and go get a new civic Si ....

BTW, it might be normal for your rad to overflow with the top off as there is more flow at higher RMPs. The no spill funnel works great so you can fill and burp the system with the coolant expanding.

 

you are aware of the f23 cracked block issue right? anyway, don't give up on the car! civic si will be bigger payments, higher insurance premiums and expensive gas only. Keep the accord. It is a great car, and it may cost you a few hundred to fix it, but dollar for dollar it is well worth it in the end.

 

Monitoring the voltage at the ECU is a great diagnostic since you do not trust the gage. This is a step I use with my Break Out Box (BOB) prototype. Work In progress.

 

have you by any chance checked the radiator cap ??

 

Super slow,
I've never heard or the cracked block issues with the F23... This is a '98 2.3 Acura CL (basically and accord with an acura tag).

Honda-Master,
The cap is new from a few months ago when the rad was replaced.


New info!
The radiator that I replaced 2 months ago appears to have a drip somewhere (there is some coolant on the plastic splash shield that is below the radiator). This is on the right side of the rad away from the hoses. Warming up the car I can't see any obvious leaks.

I called the auto parts store where I got the radiator (after market, not an Acura part). They said to have the radiator pressure tested and if it is leaking because of a defect and not damage (like a road strike of some kind) they will replace it for free. If I can't see the leak I'm going to bring it to a shop I'm friendly with for a pressure test.

I'll be happy if the issue is that simple. It would explain why my system is not staying full and also the hot spots that might be causing my gauge to jump around.

Stay tunned for more!!!!

 

OK, I got too excited too soon. I think the fluid I saw was just some spilling. Rad does not appear to be leaking. Over the weekend I replaced the Gauge sensor. Problem is still there. Seemed like air was not working out of the system when filling. I'm beginning to suspect the head gasket. The car went into my local friendly shop today for some diagnostics. He's going to hook up the car to a computer to see the ECU temp and also trouble shoot the head gasket. Should know more in a day or so.

 

ok,,

My mechanic (who is a great honest guy) does not think I have a head gasket problem. He did some kind of test that looks for gasses in the coolant and didn't find anything.

He suggested a fan switch issue since when he shorted out the front fan switch the fans did not kick on. But after some research I found out that the higher temp switch at the inlet housing is for turning the fans on when the engine is off (which is why they didn't come on when he shorted out the connector).

The fan switch on the thermo housing (the one that turns on the fans when the car is running) does seem to work since the fans kick on. But I'm confused why the fans would not be on with the higher gauge temps. BTW my mechanic also confirmed the gauge is accurate by monitoring the ECU temp. That is fluctuating up and down also.

My next step is to replace the cheapo Thermostat I installed with an Acura OEM part. If that does not work I'm not sure what to do next.

 

Some new clues from tonight...

I picked up my car from the mechanic tonight and drove home. A good 20 min drive with he gauge reading hotish, between 1/2 and 3/4 (same issue). I get home (gauge still at 1/2) and the top rad hose is hot but the lower hose is STONE COLD. Now this is making sense of why my fans are not kicking on with the higher temp gauge reading. The fan switch is on the tstat housing where the lower hose enters (the cold hose).

So what does this mean? Also feeling the top of the rad it is hot just like the top hose and the bottom of the rad is cold again. Same thing when the car is sitting at idle with no air blowing over the rad and the fans not on (we sat around and pondered for 10 mins with the engine idling).

Could the rad be working that efficiently that the water is cold at the bottom after a 20 min ride? Or just sitting at an idle? Does this mean I have no flow though the rad?

Another theory my dad had was what if the aftermarket Rad (picked it up at an auto parts store, not a dealer) was cooling too much and closing the tstat? This issue seemed to raise its ugly head when it got cold outside. For the 2 weeks that it was warm in northern NJ my temps were not getting hot.

I'm still planning to swap out the generic tstat I installed for an OEM tomorrow night. But figured I would let you guys think this over a bit.

Thanks!

 

I will be taking the head off mine in a couple of days after the gaskets arrive. I think that my problem is water pump causing no flow and then overheating which led to HG failure. When did you last change your water pump/TB?

 

TB and pump where cahnged about 85K miles ago. They are due for me too. But I don't think that is my issue now... but who knows at this point!

 

BTW I checked my rad level this morning and it was filled to the brim. I thought maybe my mechanic might have not filled properly while he was looking over my system.

Tonight the Tstat gets changed out for an OEM. Stay tuned for more!

 

My other thought is air was next to the Tstat insulating it from the hot water and not allowing it to open (I read this on a cooling system troubleshooting web site) This could be why that bleeder is right by the thermostat. If my mechanic didn’t bleed yesterday when he was poking around that might be the issue. Either way I’m swapping out the Tstat and bleeding / filling EXACTLY as it mentions in the service manual tonight to rule both those issues out…

As it states in the manual

#1, open bleeder (and I will attach a clear hose to look at coolant coming out).

#2, fill until bleeder has no air coming out, just fluid

#3, Close bleeder

#4, Run car with cap off (and in my case the no spill funnel filled half way up so the coolant level stays above the rad neck).

#5 Run until fans kick on twice.

#6 Cap rad and check for leaks

The one thing I did on previous fills was leave the bleeder open while warming up the car… And I noticed the fluid in the hose attached to the bleeder got sucked back into the system. Maybe air got in there too? This time I’m not deviating from the manual!!!!!!

 

forgot one step before step one.

Turn heater on to full!!!!

 

Here’s one an interesting point. The OEM Tstat I picked up today has 78 deg C stamped on it (172.4 Deg F). I looked up the STANT tstat I installed and it’s rated for 180 deg F.

Mmmmmmmm.

 

You are good, replace with OEM tstat and make sure the little nipple is at 12 o'clock and that the seal is properly installed, a cold radiator is a stuck closed tstat. The temp difference between the two tstats wont hurt your car.