RX4 overheating

mvander · 05-18-2023, 10:51 AM

Hello!

I have been lingering on here and adventure bikes forum for about a year, some great info, thank you to all the contributors.

My 2022 RX4 has ~3700 miles on it and starting to have a mild overheating issue... First noticed it last week at the end of an hour long ride, was getting up to 102, outside temp was low 80's. Yesterday it was hovering around 104 and made it up to 107 for a minute or so before it came back down, outside temp was low 90's. Looks like 105 is the threshold when the temp gauge starts flashing.

What kind of temperatures are you all seeing on a warm day?

Coolant looks good and is topped off. Fan comes on around 87. I saw another post on here people suggested to flush the coolant. That was going to be my next step. I had a VFR800 that was overheating years ago - put the Honda special blue coolant in, and the issue went away. I still have some of that blue stuff left.

On another note, I have had some peculiar electrical issues. The first was about 100 miles after I picked the bike up from dealership, the throttle stuck wide open going over the grapevine - pulled over, shut down, let it sit for 10 mins - and this has never happened again.

More recently the bike died out of nowhere at freeway speeds, wouldn't start for about 15 mins and then fired up like nothing happened. Check engine came on and the code was for injectors, which has since turned off. CSC said if it happens again swap one of the 3 identical relays for fuel pump/headlight/fan...

Overall the bike has been OKAY. Not sure I would buy another. I'm 6-1, the legs feel a little cramped on long rides, suspension is not pleasant but not terrible, with the gearing setup to accommodate smaller engine, the thumper is spinning pretty fast at highway speeds and does not feel overly smooth, but I'm being picky. This is a budget bike and you get what you pay for. For the price I'm pretty happy.

Edit: I also had the right support bracket tab for the windshield/headlight/cluster assembly shear at ~2000 miles. No offroad, just normal city riding... CSC recommended welding. I fixed with JB weld and a pipe clamp since it is a fairly low visibility area. Seems to be holding up. Maybe I got a lemon?

pyoungbl · 05-19-2023, 10:43 AM

Your bike should not be running so hot. My first thought is thermostat not opening correctly. If you do replace the thermostat it's good time to swap the fluid although the fluid is so new it should not be the issue. Can't hurt, though. Since the fan is coming on the only other variable is the water pump. Although you can pull the pump to check for obvious problems I'd call that a low probability of being the problem. If the pump were toast you'd see much higher temps. Overall, these bikes tend to be over cooled so your problem is one for concern.

**JerryHawk250** · 05-19-2023, 10:48 AM

You may have air trapped in the hoses.

mvander · 05-19-2023, 11:13 AM

Thanks for the replies.

Looks like the thermostat is 10$ from CSC. I’ll pop one of those in, new coolant, and try to get any air out of the system.

Any tricks to purging air, or just let it run at operating temp with the radiator cap off?

J4Fun · 05-19-2023, 12:51 PM

Just another thought here what does your oil look like after running it a bit? My thought is it could also be a cracked water jacket, hope not. If the oil looks milky after running, this could be a problem from an over heated engine. As others have mentioned air in the system and stuck thermostat could be the problem too. Just thinking out loud…

outboardr · 05-19-2023, 01:48 PM

I agree, what does the oil look like, and might want to get a spare relay along with the thermostat.
Also, what does your spark plug look like? Is it a Torch? A few of us have switched to ngk or denso plug.

mvander · 05-26-2023, 04:01 PM

Images of the new and old thermostat attached.

Appears the clip unattached from the main body. I’m suspecting this was preventing the unit from fully opening and causing fluid to not circulate properly. Hoping that’s the only issue anyways… new fluid and stays below 90 idling in the garage, will see how it acts on my next commute.

Also replaced the spark plug with ngk, it was a torch.

Thanks for the input everyone.

pyoungbl · 05-26-2023, 04:28 PM

Yep, you found the problem. It's clear that the thermostat could not open fully. Smart to throw the Torch plug in the trash. I think the bike will start easier now and run within the temp specs.

Peter Y.

outboardr · 05-26-2023, 10:55 PM

Bingo! Good job!
The proverbial “smoking gun”, that broken thermostat.
Good job on doing the ngk upgrade too.
Hope your next report is all smiles and thanks for following up on results as it helps us all.

outboardr · 05-30-2023, 01:28 PM

Mvander
There’s a fellow rx4 owner over on advrider with similar symptoms could you visit over there and perhaps post there too?
https://www.advrider.com/f/threads/c...#post-47922981

mvander · 05-31-2023, 02:13 PM

Looked through the post on ADV rider, looks like that problem is more serious, but maybe caused by the same thermostat failure?

First significant ride this morning into work - got up to 96C going 80 MPH, outside temp was mid 50's... pretty cool, the 96 was higher than I was expecting... dropped back down to 90 when I got off the highway and cruising at 40 MPH.

Will see what it does on the ride home up hill and warmer.

mvander · 06-21-2023, 11:33 AM

As a follow-up to my original question, in case anybody finds it useful...

Now that the thermostat is replaced and having tracked the temperature through a variety of conditions.

Seems like at highway speeds on a warm day, I am seeing between 90 and 97, most typically sitting right at 96.

Off highway, it tends to sit around 90, cycling down to 85 when the fan comes on.

outboardr · 06-23-2023, 12:34 PM

I"ll look at my dash and use my ir probe to record my temps, and report back in a couple days, but from memory with ambient anywhere from 30s to 70s up here by Seattle, 89-90 indicated. I'm almost never on the freeway.
2021 RX4 about 3600 miles i think

db_moto · 07-30-2023, 02:14 PM

I had posted on the RX4 thread over on ADV rider forum. My 2020 with 24k miles at the time was overheating on my way back from a trip to KY. Later I boiled the thermostat once removed and it never opened. Replaced the thermostat, drained the coolant. I ran the bike with the radiator cap off until the fan came on twice to make sure all of the air was out. I think I got lucky not over heating the bike.

omid455 · 11-18-2023, 02:55 AM

I have noticed an issue since yesterday, randomly the fan is not turning on and the bike overheats at slow traffic or behind a red light. Sometime it kicks in sometimes not. I don't know if it makes sense or not, the only change since yesterday is that simply changed the spark plug to NGK 5869. The engine runs much better now and less jerky throttle. I appreciate if some would shed a light. I suspect a loose fan cable connection or faulty relay? Thanks

05-18-2023, 10:51 AM	#1
mvander Join Date: May 2023 Posts: 11	RX4 overheating Hello! I have been lingering on here and adventure bikes forum for about a year, some great info, thank you to all the contributors. My 2022 RX4 has ~3700 miles on it and starting to have a mild overheating issue... First noticed it last week at the end of an hour long ride, was getting up to 102, outside temp was low 80's. Yesterday it was hovering around 104 and made it up to 107 for a minute or so before it came back down, outside temp was low 90's. Looks like 105 is the threshold when the temp gauge starts flashing. What kind of temperatures are you all seeing on a warm day? Coolant looks good and is topped off. Fan comes on around 87. I saw another post on here people suggested to flush the coolant. That was going to be my next step. I had a VFR800 that was overheating years ago - put the Honda special blue coolant in, and the issue went away. I still have some of that blue stuff left. On another note, I have had some peculiar electrical issues. The first was about 100 miles after I picked the bike up from dealership, the throttle stuck wide open going over the grapevine - pulled over, shut down, let it sit for 10 mins - and this has never happened again. More recently the bike died out of nowhere at freeway speeds, wouldn't start for about 15 mins and then fired up like nothing happened. Check engine came on and the code was for injectors, which has since turned off. CSC said if it happens again swap one of the 3 identical relays for fuel pump/headlight/fan... Overall the bike has been OKAY. Not sure I would buy another. I'm 6-1, the legs feel a little cramped on long rides, suspension is not pleasant but not terrible, with the gearing setup to accommodate smaller engine, the thumper is spinning pretty fast at highway speeds and does not feel overly smooth, but I'm being picky. This is a budget bike and you get what you pay for. For the price I'm pretty happy. Edit: I also had the right support bracket tab for the windshield/headlight/cluster assembly shear at ~2000 miles. No offroad, just normal city riding... CSC recommended welding. I fixed with JB weld and a pipe clamp since it is a fairly low visibility area. Seems to be holding up. Maybe I got a lemon? Last edited by mvander; 05-18-2023 at 01:09 PM.
	1

05-19-2023, 10:48 AM	#3
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,533	You may have air trapped in the hoses. __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	1

05-26-2023, 04:01 PM	#7
mvander Join Date: May 2023 Posts: 11	Images of the new and old thermostat attached. Appears the clip unattached from the main body. I’m suspecting this was preventing the unit from fully opening and causing fluid to not circulate properly. Hoping that’s the only issue anyways… new fluid and stays below 90 idling in the garage, will see how it acts on my next commute. Also replaced the spark plug with ngk, it was a torch. Thanks for the input everyone. Attached Thumbnails
	1

07-30-2023, 02:14 PM	#14
db_moto Join Date: Sep 2021 Location: Indiana Posts: 13	I had posted on the RX4 thread over on ADV rider forum. My 2020 with 24k miles at the time was overheating on my way back from a trip to KY. Later I boiled the thermostat once removed and it never opened. Replaced the thermostat, drained the coolant. I ran the bike with the radiator cap off until the fan came on twice to make sure all of the air was out. I think I got lucky not over heating the bike. __________________ 2020 Fleet: CSC RX4, Hawk 250 DLX, Moto Guzzi V85tt “You are not entitled to your opinion. You are entitled to your informed opinion. No one is entitled to be ignorant.” -Harlan Ellison- “The most terrifying words in the English language are: I'm from the government and I'm here to help.” ― Ronald Reagan-
	0

11-18-2023, 02:55 AM	#15
omid455 Join Date: Nov 2023 Posts: 1	Fan not working (intermittently) I have noticed an issue since yesterday, randomly the fan is not turning on and the bike overheats at slow traffic or behind a red light. Sometime it kicks in sometimes not. I don't know if it makes sense or not, the only change since yesterday is that simply changed the spark plug to NGK 5869. The engine runs much better now and less jerky throttle. I appreciate if some would shed a light. I suspect a loose fan cable connection or faulty relay? Thanks
	0

05-19-2023, 10:43 AM	#2
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	Your bike should not be running so hot. My first thought is thermostat not opening correctly. If you do replace the thermostat it's good time to swap the fluid although the fluid is so new it should not be the issue. Can't hurt, though. Since the fan is coming on the only other variable is the water pump. Although you can pull the pump to check for obvious problems I'd call that a low probability of being the problem. If the pump were toast you'd see much higher temps. Overall, these bikes tend to be over cooled so your problem is one for concern.
	1

05-19-2023, 11:13 AM	#4
mvander Join Date: May 2023 Posts: 11	Thanks for the replies. Looks like the thermostat is 10$ from CSC. I’ll pop one of those in, new coolant, and try to get any air out of the system. Any tricks to purging air, or just let it run at operating temp with the radiator cap off?
	2

05-19-2023, 12:51 PM	#5
J4Fun Join Date: May 2021 Posts: 258	Just another thought here what does your oil look like after running it a bit? My thought is it could also be a cracked water jacket, hope not. If the oil looks milky after running, this could be a problem from an over heated engine. As others have mentioned air in the system and stuck thermostat could be the problem too. Just thinking out loud…
	0

05-19-2023, 01:48 PM	#6
outboardr Join Date: Jan 2022 Posts: 42	I agree, what does the oil look like, and might want to get a spare relay along with the thermostat. Also, what does your spark plug look like? Is it a Torch? A few of us have switched to ngk or denso plug.
	0

05-26-2023, 04:28 PM	#8
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	Yep, you found the problem. It's clear that the thermostat could not open fully. Smart to throw the Torch plug in the trash. I think the bike will start easier now and run within the temp specs. Peter Y.
	1

05-26-2023, 10:55 PM	#9
outboardr Join Date: Jan 2022 Posts: 42	Bingo! Good job! The proverbial “smoking gun”, that broken thermostat. Good job on doing the ngk upgrade too. Hope your next report is all smiles and thanks for following up on results as it helps us all.
	0

05-30-2023, 01:28 PM	#10
outboardr Join Date: Jan 2022 Posts: 42	Mvander There’s a fellow rx4 owner over on advrider with similar symptoms could you visit over there and perhaps post there too? https://www.advrider.com/f/threads/c...#post-47922981
	0

05-31-2023, 02:13 PM	#11
mvander Join Date: May 2023 Posts: 11	Looked through the post on ADV rider, looks like that problem is more serious, but maybe caused by the same thermostat failure? First significant ride this morning into work - got up to 96C going 80 MPH, outside temp was mid 50's... pretty cool, the 96 was higher than I was expecting... dropped back down to 90 when I got off the highway and cruising at 40 MPH. Will see what it does on the ride home up hill and warmer.
	1

06-21-2023, 11:33 AM	#12
mvander Join Date: May 2023 Posts: 11	As a follow-up to my original question, in case anybody finds it useful... Now that the thermostat is replaced and having tracked the temperature through a variety of conditions. Seems like at highway speeds on a warm day, I am seeing between 90 and 97, most typically sitting right at 96. Off highway, it tends to sit around 90, cycling down to 85 when the fan comes on.
	0

06-23-2023, 12:34 PM	#13
outboardr Join Date: Jan 2022 Posts: 42	I"ll look at my dash and use my ir probe to record my temps, and report back in a couple days, but from memory with ambient anywhere from 30s to 70s up here by Seattle, 89-90 indicated. I'm almost never on the freeway. 2021 RX4 about 3600 miles i think
	0