P500 Temp light and fan come on before enjine warms up

[Rb40]

Even cold, temp light and fan come on and stay on a few minutes after starting, already changed temp sensor, no change

 

[Bastardchild]

Hmmm. That woulda been the first thing i suggested also. Im sure someone more knowledgeable will be along shortly with different ideas, but in the mean time maybe you could disconnect the battery cables for about 10 minutes to reset the computer maybe? Ecu, ecm, whatever it is. Ive heard doing this cures other electrical related things sometimes, wouldnt hurt. Just my .02. Good luck!

 

[Hondasxs]

Even cold, temp light and fan come on and stay on a few minutes after starting, already changed temp sensor, no change

Did you check both sensors? There should be an oil sensor and a water sensor.
Sounds like its lots single, default is fan auto on. Most likely just a disconnected wire.

 

[Hondasxs]

Maybe only 1 sensor for the 500 as that's all I'm seeing. The water temp sensor on top of the head.
With it unplugged, did it change anything?
The manual really doesn't give much info on it.

 

[DG Rider]

T-stat sticking closed?

 

[Rb40]

T-stat sticking closed?

Checked t stat, its good, unpluged pcm for couple of hours, unpluged t sensor, no change, runs about 5 minutes at idle then fan and temp indicator comes on and stays on till you kill enjine, let it sit a maybe 20 min, it does it again after running a few minutes, enjine never really warms up. Used it around the yard to do some weed spraying while watching radiator temp, barely warmed up---------strange

 

[DG Rider]

Checked t stat, its good, unpluged pcm for couple of hours, unpluged t sensor, no change, runs about 5 minutes at idle then fan and temp indicator comes on and stays on till you kill enjine, let it sit a maybe 20 min, it does it again after running a few minutes, enjine never really warms up. Used it around the yard to do some weed spraying while watching radiator temp, barely warmed up---------strange

Can you tell if water is circulating in the radiator? Don't know what the water pump setup is on these (how it's driven). Did it do anything else strange recently?

 

[Bastardchild]

Also, there is an air bleeder bolt for the cooling system under the seat that @jak9922 showed me. If you have an air pocket in the cooling system it will overheat. You can purge the air out of the system by taking a little bolt out of a cooling pipe roughly under the seat belt assembly in the middle of the seat. Take a little piece of plastic off from under the seat and its right under there. After i purged mine i cut a hole in the plastic to make the purge bolt easier to get to in the future. It sounds like yours says its overheating from the get-go though.

 

[Rb40]

Also, there is an air bleeder bolt for the cooling system under the seat that @jak9922 showed me. If you have an air pocket in the cooling system it will overheat. You can purge the air out of the system by taking a little bolt out of a cooling pipe roughly under the seat belt assembly in the middle of the seat. Take a little piece of plastic off from under the seat and its right under there. After i purged mine i cut a hole in the plastic to make the purge bolt easier to get to in the future. It sounds like yours says its overheating from the get-go though.

After trying every thing I and every one else and the Honda service manual can come up with I finally had an idea, I pulled the new temp sender, plugged the wires back on, plugged the hole in the head with the old sender and fired it back up, ran for 20 minutes, no temp light, used my heat gun to heat the sensor just hanging on the wires, took about 5 minutes for temp light to come on. My conclusion from that is that I have a head gadget leak, obviously the sensor was getting hot enough to turn on the light and fan before the coolant even go warm in the radiator, oh by the way I did pull the water pump apart and it was fine mechanically and the hose to the radiator warms up and you can feel It pulsing. Then I proceeded to pull the head, that's where I discovered that the 2 nuts on the head bolts under the rocker box were loose, turned them off with my fingers, when I found that the head lacks about 1/4 " of room to slide off the studs, looks like I might get by unbolting the enjine mts to let it sag enough to get it off, maybe, that's where we are now, back at it tomorrow, will update

 

[NTCPrezJB]

After trying every thing I and every one else and the Honda service manual can come up with I finally had an idea, I pulled the new temp sender, plugged the wires back on, plugged the hole in the head with the old sender and fired it back up, ran for 20 minutes, no temp light, used my heat gun to heat the sensor just hanging on the wires, took about 5 minutes for temp light to come on. My conclusion from that is that I have a head gadget leak, obviously the sensor was getting hot enough to turn on the light and fan before the coolant even go warm in the radiator, oh by the way I did pull the water pump apart and it was fine mechanically and the hose to the radiator warms up and you can feel It pulsing. Then I proceeded to pull the head, that's where I discovered that the 2 nuts on the head bolts under the rocker box were loose, turned them off with my fingers, when I found that the head lacks about 1/4 " of room to slide off the studs, looks like I might get by unbolting the enjine mts to let it sag enough to get it off, maybe, that's where we are now, back at it tomorrow, will update

I’d smash a dislike button for you if there was one. I’m glad you figured it out at least. Bummer it is taking up so much time that could have been spent riding.

 

[Rb40]

I’d smash a dislike button for you if there was one. I’m glad you figured it out at least. Bummer it is taking up so much time that could have been spent riding.

The rest of the story, pulled the head and barrel, piston was badly scrubbed and cracked, head was warped 8 thousands, probably from over heating from the gasket leak, maybe caused by loose stud nuts from factory, maybe from me overworking it, anyway after a 60 overbore and new piston, 10 off the head ,it is back together, runs and sounds better than ever, onely have a few hours on it so dont know if oil consumption is changed ( it has used way too much since new), need to add a little to the disassembly that I detailed earlier, if pulling head and barrel in the frame, take out both rear motor mt bolts and Jack up the rear of the motor, long studs will clear the cross tube behind the seat. The good part is I got it back together in time To take it back to Alaska to launch the boats, watch out ninilchik we are headed your way on Thursday the 14th of June, will try to attach a pic of the rig ready to head north

 

[Chooglin]

Glad all is well again !

 

[Rb40]

Glad all is well again !

Thanks, it had me worried that I might have to use my backup rhino up there , it's not really set up like the p 500, we also do a lot of trail riding and it's really set up for that, doors, windows, glass windshield with wipers, winches front and back, 26" big horns etc