I've been searching this forum and haven’t found an answer so thought I’d post. And I thought I posted this yesterday but I'm not seeing it, sorry if it's a duplicate. I have a 96 Accord EX 2.2 VTEC, 243k miles. I’ve had it for the last 150k miles.

Some background. I had the thermostat and upper and lower rad hoses (and timing belt and water pump) changed approx. 60k mi ago. Not sure the thermostat was OEM since it wasn’t done at Honda. Come to think of it, maybe they didn't even change out the thermostat, just said they did.

A week ago after R&Ring the shift control solenoid I finally got around to removing all the black oil/gunk (at least an eighth inch thick) clinging to the bottom half front of the engine to see if the solenoid gasket was leaking (gunk probably added to by a long-time mildly leaking oil pan gasket; had replaced 15 months ago). As a result of cleaning the engine I’ve noticed that whenever I’ve opened the hood, the hood stand rod hasn’t been so hot to hols as it always was on this car before cleaning the engine, so hot that I couldn’t leave my hand on the metal part of the rod for more than a couple seconds. So, I wondered if cleaning the engine helped to cool the engine compartment since the gunk wasn’t holding as much heat in the block. But I don’t know.

Ok, to the problem. Yesterday I was driving about 75 mph (low 70s temp outside, early evening) about 20 miles, got off the highway, parked about five minutes and once I started going again I noticed the temp gauge was up at the ¾ mark. If I slowed down on the freeway the temp would go down toward the halfway mark, speed up to 80 and the temp would rise back to ¾ mark. Turning on the heater would cause the temp to drop within a couple seconds just a little bit. Turn the heat off and the temp would go back up to ¾ or so.

When I stopped, there's no leaks, no steam, no abnormal heat coming off the engine. The radiator was full when I checked it last week, and the reservoir was half full when I checked it yesterday. I tapped on the thermostat hoping it might dislodge it, if sticking, before driving back home. That brought the temp back to the halfway mark once I started back up and drove off. But as I drove at 70 the gauge very slowly went back up to the ¾ mark, over maybe five minutes. When home I went under the hood and the hood stand rod still wasn’t hot, just only warm, as it’s been since cleaning the engine. The engine fan was working. The a/c wasn’t on so the a/c fan wasn’t on).

I'm wondering if cleaning the bottom half of the engine made it cool more naturally so maybe the thermostat was closing (inaccurately) to compensate. As logical as that might sound, it doesn’t make sense because it seems the thermostat should do its thing regardless of removing a layer of gunk “insulation” form outside of the engine lower block. Does it take some time for one of the computers to reset after cleaning off the block?

Maybe a sticky thermostat? And I haven’t noticed the gauge going up before yesterday, but I’ve only driven it maybe four times since the engine cleaning.

Hopefully not too much detail.

Any thoughts? Thanks in advance.

 

When the engine is cold, open the radiator cap and check the coolant level in your radiator.

You should have enough air flow when moving at high speeds to cool the radiator. Take close look at both sides of the radiator fins to see if you have a bunch of dirt/debris blocking flow. Look at the a/c condenser as well. If you attempt to clean, use something light coil-clean that you can get at most home improvement stores. Use light water pressure from your hose to clean off, because high water pressure can bend the fins.

When the engine is running, the radiator and a/c condenser fan should turn on to cool the engine when the coolant gets above a certain temperature. On the 96, the radiator fan will turn on when the engine is shut off to prevent heat soak. I don't think the fans are your issue, but a quick test is to start the engine and turn on the a/c. Both fans should turn on.

 

Thanks PAhonda. Engine cold, radiator couldn't be anymore full, reservoir halfway full, both as should be. Both front and back of the radiator and condenser have no debris, looking quite good. Radiator cap seems fine, both valves move separately when compressed with my thumbs (but I knew that wouldn't be an issue since it wasn't spitting any fluid when hot yesterday.


I started the engine (first time today), what struck me immediately is that the temp gauge needle shot up from the bottom up, where it sits when off, to where it would normally be once at operating temp, fully warmed up, and did so in a second, literally. Then it stayed right there for the 15 minutes I let the car idle, not moving at all. Hmm.

After a couple minutes of running I started the a/c, the radiator fan came on but not the condenser fan. I did this three more times over the 15 minutes, same result. The refrigerant has been fine, plenty cold.

It was interesting to me that the rad fan never came on during the whole time except when I turned on the a/c.

The upper rad hose eventually got too hot to touch, the lower hose got barely lukewarm at most. Again the rad fan never came on except with a/c, which is puzzling, making me wonder how the lower hose didn't get hot since there was no fan(s) cooling the rad. Unless the thermostat was stuck closed, not circulating the coolant?

After I turned off the engine I thought the rad fan might come on, but it didn't. Maybe I didn't get it hot enough. Granted the hood was open the whole time, preventing heat build up in the engine compartment.

So, the temp gauge movement is strange, don't know what to make of it. Anyone with a Honda knows it takes a few minutes to go from bottom to just below midway on the dial (normal operating position).

I don't think a bad thermostat would cause the gauge to act that way, jump up to normal position (never has in the past). And I don't think it would be closed if the upper hose is very hot. But I'm not experienced enough with this issue.

I'm stumped here. I'd appreciate any thoughts you have on this. Thanks again.

 

When cold, squeeze one of the radiator hoses repeatedly. Listen & feel for sloshing - there should not be any. You might hear a tiny sound from the little vent-pin in the thermostat, but I've found that air/water sloshing is rather distinctive.

Hondas don't like air to be trapped around the thermostat. If you feel anything like that, there's a bleed vent on the T-stat housing (looks like a brake bleeder valve).

Now the temperature gauge. It's not possible for the actual temperature to climb instantly when you first start the cold engine. That seems like an electrical short in the sender wire. The temperature sender is in the cylinder head somewhere below the distributor. It has only 1 wire. If that wire is pinched somewhere & shorted to ground, that will send the temperature gauge high. Or maybe the sender itself is messed up.

Nearby there's a 2-wire sensor that measures coolant temperature for the ECU.

On the T-stat housing is another "sensor" which is the fan switch. Unplug that one & short between the wires with a paperclip. Key on, that should make both fans run. Probably only one will run, just like when you switched on the AC.

https://www.hondaaccordforum.com/for...sensors-39096/

 

Jim, thanks for your inputs. Since I wasn’t familiar with the coolant circuits I didn’t know what to make of your suggestions, so I studied up.

The short of it is I did three different tests on the sender unit, all said it was bad. Then out of curiosity I cleaned up the sender wire since it was corroded inside, and banged on the sender with the end of my ratchet wrench. Works perfectly now. God I love simple fixes! But I ordered a new one since my fix is probably temporary.

I had assumed there was no air trapped in the system since I had bled it out a few years ago when changing out the upper hose. And since the rad has always been full to the top I didn’t see how any air would get in there; not to say I’m right about that.

Since the car was running fine when the temp gauge was wacky I figured the “D” switch (to ECU) was probably okay. Seems to be a non-issue now that the gauge is working fine.

Yeah, I heard that pin-jiggling sound in the t-stat when squeezing the upper rad hose, which was firm, no water sloshing around. But I ordered a new OEM t-stat for 18 bucks (eBay) as a backup.

Regarding the condenser fan, jumped the “A” switch pins, no condenser fan. Then did a jump directly from the battery and a block ground to the motor wire pins. It appears the motor is out (which is weird since I’ve rarely used it, maybe 5 minutes at a time a handful of times each summer over the years, just to make the cabin tolerable; prefer fresh air to a/c). The fan spins freely by hand. Maybe a corroded connection, I’ll look further into it.

And I discovered my coolant needs changing per a voltage test (never heard of it before); bad coolant if over 0.3v (mine is 0.42), can corrode internal engine parts. Wondering if old coolant can cause erratic temp gauge movement.

Thanks again.

 

Honda uses their legacy terminology for the "radiator" fan & "condenser" fan because years ago the radiator & condenser were side-by-side. Several years before your car, they switched to full-size stacked and when the engine temperature calls for the fan they both run. So you've run your "condenser" fan more than you think.

For your coolant, it's the anti-corrosion additives that get used up. Not the ethene glycol itself. The voltage test is measuring corrosion as it's happening.

Who knows if the sender problem is related to the antifreeze, but repairs by hitting something are usually not very permanent.

Glad you're on the way to getting it sorted out.

 

Ah, that's a very useful understanding about the two fans, been using the cond. fan more than I thought.

New info: when I start the car cold, the gauge goes immed. to the normal position as if the car is already warmed up, but it doesn't go any higher while driving for 20 minutes. Interesting. Hoping the new sensor unit will get the gauge to act normally.

I probably didn't need to do the voltage test on the coolant itself since it's been too many years/miles since I've changed it, surely too old. Regardless, I thought it was an interesting test to do, and very easy.

In looking into how these coolant sensors and switches operate, I'm wondering if the "D" sensor/switch that goes to the ECU could be going bad, a different symptom: for a several years now whenever I start the car, whether summer or winter (here in San Diego, not very different) the tach always goes right to 1700 RPMs to idle, which is high. When warmed up it idles at about 800-850, a little high. I haven't bothered with it since the car has always run fine. It first seemed to happen around the time I cleaned out the IAC valve (the little screen was somewhat clogged). I thought the computer would correct the idle, but never did. I bring this up because the car bucks when putting it into gear more than I'd like for this old car. Any suggestions on this? I wait the usual 30 sec for the oil to circulate, but the idle doesn't come down much in that time.

Thanks again, Jim and PAhonda.

 

Computer control of the fast-idle (via the IACV) didn't start until 1998.

Your car has a fast-idle-thermo-valve which I think simply operates on the temperature all by itself. It has coolant running through it, so if that's blocked by some crud then it won't see the correct temperature.

I don't remember the details, but search here and in the DIY section for a thread about taking the FITV apart & cleaning it & tightening the plunger. I never had an Accord of that generation, so I don't have first-hand experience with that.

Finally, the DIY section has a thread started by me about setting the BASE idle.

 

Jim, sorry for the delayed response, took me awhile to do some necessary research and then get to fixing it. You're right, it was the FITV. I screwed it down to snug. Cold idle is now 1,200 rpm instead of 1,750. Thanks again for your help. All you guys help make my life under the hood much easier.

 

Thanks for the response. So many times we never hear back whether it's resolved or not.