Quick Background:
‘98 2.3CL 210K miles
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?

 

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!!!

 

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!

 

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 ¼ - 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 ½. 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 ½ 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 ½ on the gauge I shut the car off and turn on just the ignition. The gauge bounces down to ¼. Fire up the engine and it goes back to ½. 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. I’m not sure what’s involved with that. I know the ECU sensor is right next to the gauge sensor. Is there a handheld thingy out there that can be plugged into the ECU connector (I think it’s the one behind the ash tray).

 

are the fans kicking on when you drive? or just when you turn off the car?

 

The fans kick on like they normally do (like when coming to a stop and idling for a min). But they are not on when the gauge is reading at the half way mark.

The fans work off of two temp switches not the gauge sensor.

My local autozone has the gauge sensor in stock for 15 bucks. I'm going to swap it out this weekend for the hell of it to see what happens and to rule it out...

 

try a more expensive thermostat, the cheaper ones tend to not be very accurate when they open and close.

 

If you have an Obd2 scanner w/ monitoring features, you can monitor the coolant temperature (not same sensor that drives gauge) and see if the temp changes are real or false sensor problem.

I bought a scanner (Harrison Eng. Obdscan) several years ago that works w/ a older laptop (~$200 total inc. laptop). It has been a really useful tool for problems such as yours.

I also would suspect the thermostat, particularly if it's not OEM. Even though you tested it may not be fully opening all the time.

Interested to hear of the final resolution.

regards

 

Texas,
The tstat opened great while in the pot of water at the specified temp (forget what it was off the top of my head ) but who knows…

New info!

I filled and burped the system using a no-spill funnel a few days ago (the no-spill funnel is great) and my water level has been going down slightly each day in the reserve and in the rad after a few days.

But get this. The radiator I replaced a few months ago appears to be leaking. There is some coolant under the rad on the splash guard underneath. And it’s on the right side away from the hoses. I watched the car warm up but there is nothing obvious dripping out.

I called the auto part store where I got the rad (after market, not Acura) and they said if the rad is leaking from a defect and not damage (like a road strike of some kind) that they will replace it for free. They said to have it pressure tested to make sure. Since I don’t feel like springing $100 for a pressure tester I’ll bring it to a garage I’m friendly with next week if I can’t see an obvious leak.

I’ll be happy if the issue is that simple. It would explain why my system is not holding its level and possibly causing some hot spots that are making the gauge act funny.

BTW, if and when I drain the system to replace the rad I'll toss in an Acura Tstat for the hell of it.

Stay tuned for more & thanks!

 

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…

 

There are two methods to avoid air pockets; fill very slowly allowing system to vent air out the radiator, or bleed air from the bleed valve on the thermostat housing. I've found that I can completely fill by slowly adding coolant w/o trapping air.

good luck

 

ya when I did it yesterday I used the bleeder on the tstat housing. And used the no-spill funnel to allow the system to heat up in the propper way with the cap off.

I hope my mechanic can find something silly with a presure test and/or ECU test. We'll see!!!!

 

Not looking good.

My mechanic is seeing bubbles with the rad cap off and the engine warming up. He’s going to do some kind of test tomorrow that detects exhaust gas in the coolant.

With the engine having 210K miles is it going to be worth it to do a head gasket (assuming that’s what it is). I guess if it’s something like a cracked head I won’t know till it comes off.

Also with an engine this old is shaving the head a good idea? I would imagine the increased compression puts a strain on the other components of the engine.

The engine still runs well and smooth if that makes a difference.

 

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.

 

The thermoswitch A (near the distributor) should turn on when coolant reaches about 194F. If it's not closing when your temp is high, it could be the problem or part of the problem. However, the thermostat seems more likely since forward speed of 20 mph or more is adequate to provide cooling air w/o fan support. Try replacing the thermostat and be sure to completely fill the radiator and engine w/ coolant.

good luck

 

Thanks Texas!

I'm picking up a tstat from the acura dealer tomorrow. I'll fill the rad the propper way by using the bleeder and my no spill funnel.

I'll report back tomorrow night.

 

Some new clues from tonight...

I picked up my car from the mechanic tonight and drove home. A good 20 min drive with the 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 was just looking at your problem (my first post read on this site)

-Noticed that nobody has suggested water pump. Have you replaced your timing belt recently? The water pump may be worn out (if oem). Just an idea. Hope it helps.

 

yes the water pump has about 85K miles on it and is due. But I don't think that is the issue. With the no-spill funnel on the rad you can see plenty of water agitation when revving the engine.

 

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 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.

 

Ok I replaced the STANT aftermarket tstat with the OEM tonight (this one made by Nippon according to the Acura part #, made in Japan). I can say the two tstats did not look alike at all. Completely different construction (Now I wish I took a photo).

Anyway, installed the OEM and filled the system exactly as stated in the service manual. Started the car… 1st the top hose heated up, then the bottom hose got warm / hot as the car got hotter. Fans kicked on like normal and the gauge never got above the 1/4 - 1/3 mark. Went for a ride, and it stayed steady!!!!!

Lesson learned!!!! When it comes to a component that has a specification or an important function use OEM! Sometimes you get what you pay for… Know when to say Yen!

The one thing I don’t understand. If I had a faulty tstat and it was not opening shouldn’t my car have overheated? I mean it did get warm (about 3/4 up the gauge) but it did not run away.

Thanks for listening guys and for the help!

 

glad you fixed your problem.

 

Ya the other thing I’m going to do toady is pick up (or order) an OEM rad cap from the dealer. The cap on the aftermarket rad I got a few months ago says 13 lbs on it. I know the manual says to test the cap to 14 -18 PSI. I realize that’s not a huge difference but this whole tstat experience has me a bit paranoid with aftermarket parts that have an important function. Of course I did not keep my old rad or cap. That was before I knew the rad cap was a dynamic part of the cooling system (not just a cap). But now I think I could write a book on cooling systems.

Thanks again!

 

So I picked up an OEM cap today. It turns out the stopper on the spring is at a different dimension than the aftermarket one on the aftermarket rad. It can’t be used. Oh well…

 

oh, i could of told you that if i saw this earlier, the oem one is a little bit bigger than the aftermarket one, but it still works.

 

mmm,, it's not bigger but the seal that is on the spring is taller on the aftermarket than the OEM. If you put them both cap side down on a table the rubber seal would be higher up on the aftermarket over the OEM. I don't think the OEM would work the proper way on the aftermarket rad.

 

I've had thermostats that would stick cold, then bounce up to high, and then overcompensate to cold again. I've found that OEM thermostats are much better than the inexpensive aftermarket t'stats, particularly when it comes to warmup time. The Honda/Acura T'stats will usually show operating temp in < 5 mins of driving. I've seen some aftermarket t'stats that took at least twice as long. On a cold day, I've gotten warm air in the cab w/i < 2 mins,...that's worth a little extra.

regards

 

Good point Texas. The funny thing is I did not pick up a Tstat at autozone to save $$$. I was doing the revamp of my cooling system over a weekend a few months ago. Got every hose I needed from the dealer. Then while swaping them out on a Sunday I figured, what the hell, I should replace my tstat also. Just picked one up from Autozone because it was a Sunday. Didn't think twice about it. Lesson learned!!!!!

 

BTW, I learned lots about the cooling system in my car and cooling systems in general during this whole ordeal. The one thing that pissed me off was some lack of info in the Acura service manual. They explain that there are two fan switches, and how to test each one (they come on at different temps). But they NEVER explain that the switch on the outlet housing operates the fans with the CAR OFF. Even the trouble shooting guide says “if fans never come on”. If it wasn’t for a post I read on honda-tech.com the mystery of the two fan switches would have never been solved. Oh and even the electrical diagram is no help. You can figure out that the switches turn on the relays, but not that the one only works when the car is off. This is why my mechanic was chasing a possible bad fan switch or wiring when he could not get the fans to kick on by jumping the fan switch B (with the car on).

OK , rant over…

 

In my manuals (Honda and Acura), but I don't have a CL manual, the explanation of engine off fan operation is at the bottom of a large graphic page which shows location of components including Thermoswitch B.

regards

 

I can’t find that paragraph anywhere in my manual. But I do have a CD version so maybe it’s just missing…

Thanks again!