I did a search here and it looks like I might have a bad switch for the fans. Temp normally runs a little under 1/2 way, but the other day I noticed as I slowed to turn the gauge moved up to about 75-80% of the way to hot (still not to the mark, but not where it should be). Moving along on the highway it hovers between 50-60% (again, in relation to top/hot mark). Fans do not seem to be working unless I turn the AC on, but with AC on both fans are running. Temp Gauge still fluctuates with AC on (so fans are running), never getting quite HOT, but I've had this car for 15 years and I don't like that gauge moving. Is the sensor for the fans the same sensor that runs the temp guage?

At 250K or so I had to put a new radiator on the car (not OEM, Oreillys with lifetime warranty), new tstat (also from Oreilly), new coolant,and new hoses.

I'm going to jump that switch/ check fuses tomorrow and see if the fans come on. That will hopefully be an easy fix, but I'm still concerned about the guage moving even with AC (and thus fans) running.

Car has 336K, uses no oil, and is not losing coolant.

Thanks!

 

No, the sensor to turn on the cooling fan is different from the sending unit that controls the temperature gauge.

When the car is cold, check that the radiator is full of coolant and that the overflow tank has the proper coolant level too.

If you are in a bind, you can turn on the heat with outside air full blast to help cool down the engine.

 

Coolant is full. I can turn the temp on the AC controls to about 1/2 between hot and cold and that brings the temp gauge back to it's normal spot. The gauge doesn't ever get all the way up, but I put about 3K/month on this car so I'd like to have it right.

I'll check it over probably saturday AM and see what I can find. Wonder if the tstat might be stuck 1/2 way open or something?

Thanks for the response. If anyone else has any insight on what I should be checking it would be appreciated.

 

Interestingly enough, driving the car around town today (to and from work, to lunch etc) the temp gauge went to it's normal spot and not any higher. It behaved this way both times I drove the car, and didn't move regardless of whether the AC was on or off (and thus when the fans were on or off) so I'm leaning towards the thermostat sticking 1/2 open on certain trips.

Does that make sense or am I rationalizing hoping it's something minor like a tstat?

 

I agree w/ your diagnosis of sticking thermostat. I would try an OEM thermostat. I've found that aftermarket thermostats are slow to warm and don't hold required temp as precisely as OEM.

good luck

 

Well, to update this, the car has been running cool (temp gauge in normal spot) since 10/31, including a couple of rips that were > 200 miles each way. I figured I'd keep an eye on it and if it acted up again swap out the tstat.

Tuesday I put about 500 miles on the car and about 2/3 of the way into the trip I look down and the temp gauge was up about 80% of the way to the top of the gauge. This was cruising down the interstate at about 75 mph. I kicked the heat on high, and that cooled it down a little bit (not much, I watched it like a hawk), but it still wanted to stay up around 3/4 of the way to hot on the gauge.

Yesterday morning I went to the Honda dealership and swapped in an OEM tstat. Driving home yesterday it ran a little bit cooler, but temp gauge is stillgetsup to about 70-75% of the way to hotat crusing speeds (75mph, 3K rpm), and will drop to about 1/2 way mark if I cut the heat on full blast, so I ran home yesterday with sunroof open and heat on all the way. What I did notice was if coasting (still moving 75ish) that the gauge would start moving up, and when driving around town the gauge seems to go down as the engine is revved, but moves up pretty quickly at idle. Given that the fans are electric (not affected by engine speed), and that I have a new tstat, could this be a water pump going south on me?

Thus far
New radiator about2 years ago
new OEM tsat wed
no leaks/ coolant is full and was replaced with rad

The only things I can think of would be a bad water pump or a hose that is partially collapsing. Hoses felt firm at idle (when car tries to run hot) and hoses were replaced with rad.

Thanks for any input on this. I have been debating trying a timing belt and water pump for awhile anyway, as I am overdue. If this IS a bad waterpump I need to bite the bullet and get it and the timing belt changed.

 

I have heard of water pump impellors corroding so badly as to reduce their ability to circulate coolant. If your system has had normal coolant replacements (every 2-3 yrs at least), this seems unlikely. However, if this is original water pump I would not discount the possibility.

Have the timing and balance shaft belts ever been replaced? If not, then TB's and water pump are certainly due.

One other possibility is a partially blocked radiator. This seems unlikely w/ a 2-yr old radiator.

It could be the temp changes are not real.There is a possibility of a faulty gauge or coolant temp sensor.The coolant temp sensor is under the distributor. You check the gauge by removing the connector and grounding the connector. Turn keyswitch to ON and observe coolant temp gauge. It should move rapidly towards H. Turn key OFF before gauge reaches full range or gauge can be damaged. If gauge checks OK measure resistance of sensor relative to ground. Resistance at 133F= 142 ohms and at 185-212F = 49-32 ohms. Anywhere close to these values would probably be a good sensor.

good luck

 

Thanks for the help Texas. I found the FAQ on overheating here on the site (doh!) and bled the system today on my lunch break and while the rad looked full the overflow bottle was low so I topped it off. Drove it to work and back and it was running at normal temp again. I wonder if I might have had some air in the system. I'm going to replace the fan switch on the tstat housing this weekend too. I checked it and it's bad.

I'm taking it on a 150 mile-ish trip tomorrow and will see how it goes.

Thanks again for all the help.

 

TexasHonda:
I have thinking about your car. Could the noise be from the starter and flywheel and not from the front of the engine? It would be high pitched.

 

It is definitely from the timing belt region. Your suggestion that the harmonic balancer/crankshaft pulley is rubbing on the lower timing belt cover may be correct, although I did not see any evidence when I removed the cover. However, at that time I was convinced the timing belt parts were probably at fault. That proved wrong.

The noise seems to have increassed slightly since I removed the cover last and is now slightly noticeable at idle and when engine is coasting. I plan to remove the wheel, and wheel well cover and lubricate between timing belt cover and crankshaft pulley. If there's rubbing the noise should stop for a while. Not sure how I might fix this except to addsome thin shims between pulley and crankshaft end to push the pulley slightly further away from engine.

thanks