huidaman

I have a 1998 Honda Accord EX 2.3L Vtec (F23A1) that's been acting strange lately with regards to its cooling system.

When I bought the car about 7 months ago, I noticed there was a small coolant leak (a couple of drips every time I drove the car) where the Upper Rad Hose connects to the head (I assume that's the thermostat).
I pretty much forgot about it for the longest time until recently.

I noticed my car would take a bit longer to get to temperature (a bit below half), and the odd time the heat would go warm, not hot, when I stopped at a set of lights.

So I checked the rad one morning, and noticed it was low. Not empty, but just low. So I put a bit of pure green coolant in it, filled up the rad. I started it, and it took almost forever to get to temperature. Even longer than before.

I put the rad cap back on and drove it around the block a little bit. It got to temperature (or a bit below it), and pulled into a parking lot. I noticed that the upper rad hose was still stone cold, so I drove around a bit more. After about a 5 minute drive, I pulled into my parking lot and checked it out again.

The upper rad hose was warm, lower one was warm as well. So I bled it (rad cap off, let it run for a few minutes). After what seemed like most of the air bubbles were gone, I put it back together and shut it off for the night.

Next morning, and every other morning since then, I notice that it gets to temperature fine, heat is great, and everything. But I noticed that after every drive, although the upper rad hose is hot, and so is the top of the rad, the core of the rad and the lower rad hose are cool, although after sitting in traffic, it's warm at best. It doesn't pressurize, either.

However, I notice that when I take the rad cap off and rev it, there seems to be little-to-no flow, however the levels do rise and fall when I rev it. However, the coolant that I filled the rad up with sank to the bottom no problem, like there was no blockages.

Did I mention that throughout all of this, it's never overheated once?
Oh, and the overflow tank was empty when I started having these problems. It has a bit in it now, though.

I'm going to change the upper rad hose, thermostat, and flush the system this weekend, but would like to know your opinions here.
I was told that the F23A1's aren't common for having headgasket problems, but I don't want to rule that out. I don't see any bubbles in the system, no oil in there either, and no coolant or anything in the oil. The exhaust's clean, no smells, and the plugs look their normal tan color.

jdowen2

Thermostat is a good bet.

huidaman

That's one of my thoughts, but I mean after the car warms up, the upper Rad Hose is hot. Until then, it's fairly cool.

I'd like to add a correction that it's only the bottom part of the radiator that's cold after driving on the highway. I was feeling the wrong Rad :D
The bottom part is cold to the touch after driving on the highway. I'd assume it would be at least warm. It's only warm after the car idles for a good 10 minutes after any sort of driving.

Water pump seems to be working fine, otherwise I wouldn't get any heat in my heater, right?

DCFIVER

If you not experiencing problems, what are you trying to accomplish?

holmesnmanny

1) The thermostat is at the end of the lower hose. Just follow it from the bottom of the radiator. Where it ends up, that's the thermostat housing. It's not inside the upper radiator hose housing.

2) Contrary to what most people believe the flow of the coolant goes from the water pump on the driver side across the firewall, past the thermostat and UP the radiator, though the engine, and back to the water pump. The reason your lower hose is staying cool is because the thermostat stays closed until the coolant behind it warms up enough to open it.

Lost Again

Well I guess I'm not most people why else would the "pill" on the t-stat be pointing into that "tube" that comes from the wp.

Glad your AC is working now

huidaman

Okay, so a little update.

I changed the upper and lower hoses, the thermostat (MotoRad brand), thermostat gasket, and water outlet o-ring. No more leaks.
I also drained the old fluid from the rad and replaced it with new coolant. I've been slowly topping it up with distilled water. I would have flushed it fully, but I didn't have the time or the tools to do it properly.

The lower radiator hose is still cold, however. So I'm gonna bleed out the block using the bleeder screw located on the thermostat housing on Friday when my replacement bleeder valve comes in from Honda (the on one on there is SUPER rusty), and also replace the rad cap (Honda OEM).
The temperature gauge still acts exactly like you'd expect it to. However, this time I got my OBDII scanner out and pulled the live data from it, and it says it's running at roughly 184ºF when in traffic, and anywhere from 188.4ºF to 195.8ºF when driving down the highway, which I assume is rather hot for a car with at 170ºF thermostat. It was doing this before the thermostat change, by the way.

So this leads me to a couple of new questions:

First of all, how many temperature sensors does my F23A1 (2.3L Vtec) have on it?
I noticed this one: (on the thermostat housing)


And this one: (under the distributor)


On the first picture, I'd like to know exactly what this is. It couldn't be a temp sensor, because it comes after the thermostat. So is it a fan switch? I unplugged it while the car was running and nothing happened.
On the second picture, I'm assuming that THAT is the temp sensor?
On a related note, what is the sensor right in front of it? Oil pressure switch?

jdowen2

170 degree thermostat opens at 170 degrees. If you're running 185-195 I don't think you are having a problem.

huidaman

But shouldn't the car be running cooler while on the highway than in traffic?
I also haven't heard the rad fans come on in a looong time. Only when the A/C is on.

EDIT: I forgot to mention it's been around 32ºF out for the past little while, if that makes any difference.

Fitz Williams

iTrader: (1)

I agree. Sounds like good numbers to me. If you want to run cooler then you probably need a bigger radiator. But I really don't think you need it to run cooler. The motor is built to run those temps.

huidaman

I may be being a hard-head here, but I'm still not really convinced all is well. Can someone go out and check their Accord after a long drive? Is your lower rad hose hot? Warm? Cool? Cold? This-thing-feels-like-it's-been-sitting-out-all-night stone cold?
That last one describes mine. All the time. The whole hose.

huidaman

UPDATE:
I just bled the cooling system using the bleeder bolt on the thermostat housing, and replaced the rad cap.

A constant stream of coolant came out when I opened the bleeder valve with the engine and rad cap off.

Just out of curiosity, I opened the bleeder valve while the engine was running, expecting a jet stream of coolant to shoot out, but nothing. Only coolant came out when I squeezed the rad hose with the rad cap on, and it simply dribbled out by itself when the rad cap was taken off.

Shouldn't the coolant be under pressure in there? Is this a sign of a failing water pump?

holmesnmanny

It doesn't sound like there is anything wrong with your car.

holmesnmanny

I stand corrected. It looks like 6th gen accords use a 170 thermostat. Be that as it may, I don't think there's anything wrong with your car.

DCFIVER

Again I ask what you are trying to accomplish? There does not seem to be anything wrong with your vehicle.

The thermostat is there to keep the engines temperature consistent. Operating temp on most Hondas is 180-200 F ( for most vehicles in fact.) The temp range of the thermostat is not the same as the operating range of the vehicle. It does not matter if you are in stop in go traffic or running WOT on the freeway, your engines temperature should not deviate from the operating temperature. Ambient temperature also has little to no effect on the operating temperature, again, this is becuase of the thermostat. ( extreme ambient temp swings are the exception. Even a closed loop system has its limitations)

huidaman

First off, I'll say that last night, there was actually flow through the rad (both hoses were hot), but that wasn't until the ECTS read 204ºF when the car was idling in a parking lot. I turned the A/C fans on (they didn't come on by themselves...I'll be replacing the fan switch), and the temps went back down to 186ºF. The lower hose went cold again shortly after.

There is also pressure in both hoses now that I fixed the leaky upper hose.

I'm going to bleed the system once more, but if this doesn't do anything then I'll finally admit that all is well.

But what I don't understand is pretty much this:
- Starting the car and letting it idle, the temps will climb at a fairly normal rate, but won't go any higher than ~160ºF.
- Start driving the car in the city, and it will go up to 184ºF and hover around there (rad fans don't come on)
- On the highway, the temps jump up to 194ºF, but don't go any higher than 195.8ºF
- Get back off the highway, they will go down to 184ºF again (rad fans still don't come on)
- Park the car, they will go up to 190ºF typically. Only once have I seen them go higher (last night), but the rad fans still don't come on


With that one exception, every time I've checked it, the lower rad hose is ice cold. I've never heard the fans cycle on, and turning the A/C on (which turns the fans on) doesn't bring down the temps whatsoever. If anything, they go up.



tl;dr? With the exception of one occurrence, as the amount of air that passes through the rad increases (i.e. there's a load on the engine), so do the temps.

holmesnmanny

I'm gonna try to answer to the best of my ability

If your thermostat is working properly, and it's set to open at 170, it's not going to open at idle if your car is at that temperature because it's not 170 yet. Your car is simply not working hard enough to get over 160 yet.

I know on cars with thermostats that open at 180, it will be fully open around 195. The fans don't come on until it gets just above that point. Since your car has a 170 thermostat my best guess is that it's going to be fully open around 180-185.

When you're on the highway you are cruising at around 2500 or 3000 so it's putting an added strain on the motor so it's going to get hotter. The thermostat is set to be completely open at 185 or so, so when it gets below that tempature, it will close and temperature will go back up until it stays around that temperature. Keep in mind that when driving fast, cool air will cool the radiator more than the fans would.

Again, since you're not putting a strain on the motor anymore, the temperature is going to go back down. This is why the fans run more when the car is stop and go, because the cool air isn't cooling the radiator anymore.

If you rev the car while at a stop at around 3000 rpms you will see the fans will come on because cold air isn't cooling the engine. If they don't then the car will overheat. You can try this.

Turning the ac on puts an added strain on the engine.

As the temperature goes up so will the pressure in the system.

huidaman

I appreciate your response, thank you. I have a pretty good understanding of how a cooling system works, but any help is welcome.

The problem I'm having is that even though my car is idling around 190ºF, the lower rad hose is still ice cold even when I'm stopped. I would assume my thermostat would be defective, but it was doing this before with the old thermostat.

My temps did go up to 207.6ºF according to my OBDII scanner again earlier today. This seems to be a sweet-spot where my thermostat finally decides to open, and both hoses become hot, however it would seem it's 30ºF too late.
Even though I was stopped in my parking lot, hood open after a little drive on the highway, the rad fans didn't come on. I just replaced the fan switch on the thermostat housing, too. Is there a way I can test these wires? I don't want to just short the two wires and risk damage to something else.
Turning the A/C (fans) on almost immediately brought the temps down to about 188.6ºF, but almost just as quickly, the lower hose started to lose heat. More than it should have from just the fans being on, too.
From time to time I'll notice that simply revving the engine will bring the temps down a little bit, too.

I'm also probably going to replace the rad, because I noticed there was a little bit of steam coming from possibly the upper core of the rad around the cap when it was over 200ºF today, though I doubt this will fix the problem, as it pressurizes and flows through fine.

holmesnmanny

As long as you went Honda OEM on the thermostat the thermostat isn't going to be an issue. You can use test leads to jump the fan switch by applying direct battery voltage to both terminals if you want. Again, if you went Honda OEM on the fan switch(which is located at the end of the lower radiator hose towards the back of the engine, and is situated inside the thermostat housing) you won't have a problem.

The problem with aftermarket cooling system products is you are saving a few bucks for what's a very critical car part.