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Rollos

Overheating. Could it be the thermostat?

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First summer riding everyday and I'm overheating in heavy traffic when the temp is above 80°. I see the engine temp creep past 230 and start praying for a little open road to get enough airflow to cool back down. Fan is running on cue but doesn't seem to drop temp, only slows the climb a bit. Last few weeks I've had to pull over twice to let the bike cool since it went over 250. Fan doesn't run with the engine off which isn't helping. Shouldn't it be running?

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First summer riding everyday and I'm overheating in heavy traffic when the temp is above 80°. I see the engine temp creep past 230 and start praying for a little open road to get enough airflow to cool back down. Fan is running on cue but doesn't seem to drop temp, only slows the climb a bit. Last few weeks I've had to pull over twice to let the bike cool since it went over 250. Fan doesn't run with the engine off which isn't helping. Shouldn't it be running?
First check your coolant level. Last year I was surprised to find mine low and it was running hot. Personally, I've never been able to see the level through the little slot. I remove the seat, pop off the cap and put a wood chop stick in to check the level. This method also allows you to check the cap - when my coolant level was low, I think it was because the rubber cap was partially lifted off the lip.
My 2014 still runs hot in traffic on hot days, but when the fans come on at 225F, it cools down to 215F pretty quickly.

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How long does it typically take to hit operating temp? Another reason I'm suspecting the thermostat is it takes 3-5 minutes to get 165°

 

And thanks 4corsa, it looks like I've got enough coolant through the site window but I will double check by opening up the reserve

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Depending on the air temperature, 3 to 5 minutes to get up to 165F sounds about equivalent to my 2014. I haven't actually timed it, but can do so if that would be helpful.
It certainly could be your thermostat, they can get stuck partially closed, but would be unusual on a bike less than 10 years old.

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What is a safe/normal upper limit for operating temperatures?
I've heard it depends on for how long and if at high load/rpms, but if you're just stuck in traffic for 5 -10 minutes at low rpms, 230°F is ok. The fans kick in by 225°F so it really should never get to 230.

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I wish the fan ran with the engine off. Any reason why it's wired not to?

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8 minutes ago, Rollos said:

I wish the fan ran with the engine off. Any reason why it's wired not to?

Two thoughts on that.  One would be that the fan is a large current draw and the battery is relatively small,  the other is that when the engine is off the coolant is not circulating,  so the fan will only cool what's in the rad,  but isn't going to draw heat out of the engine.  If you want that functionality,  a fan override switch can be installed.  Use it to force the fan on and allow the engine to idle to move the hot coolant out to the rad.  

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Yeah I suppose a water pump would need to be functioning too for the coolant to circulate. 

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8 hours ago, 4corsa said:

First check your coolant level. Last year I was surprised to find mine low and it was running hot. Personally, I've never been able to see the level through the little slot. I remove the seat, pop off the cap and put a wood chop stick in to check the level. This method also allows you to check the cap - when my coolant level was low, I think it was because the rubber cap was partially lifted off the lip.
My 2014 still runs hot in traffic on hot days, but when the fans come on at 225F, it cools down to 215F pretty quickly.

Sent from my Pixel 2 using Tapatalk
 

How many inches below the top is the high line?

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It's about an inch. But don't worry if you over fill a little, there's an overflow tube.

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12 hours ago, Rollos said:

Fan doesn't run with the engine off which isn't helping. Shouldn't it be running?

Fan on the 8gen has no Thermo Switch and is controlled by the ECM, so with ignition OFF Fan cannot run! 

Further to what Cogswell mentioned, it probably saved Honda money in wiring and the cost of a Thermo Switch. Keeps the system simpler as the ECM already knows the Engine Coolant Temp.

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Checked coolant this morning and added about 6 ounces to bring it up to the fill line. I let the bike warm up then rev'd to 5k RPM to bring the temp up to 225. No fan. 230. No fan. 240. No fan. Turned bike off. 

 

I have Gremlins. The fan was working fine yesterday. 

 

I booked an appointment at my local Honda for a warranty repair in two weeks. I'll be riding it like it's an airhead until then. 

 

So now I'm thinking thermostat, and fan wiring since the fan still turns so probably not a seized fan motor.

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Rollos. You sure your bike is still under warranty? Are you up to checking a few things? At least check the state of your fan fuse in the right side fuse box under your seat. Let's know if you want to check anything else or you just want to leave it to Honda.

Good luck with your bike.

 

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I am under the 4 year Honda care I bought with the bike last year but I'd love to narrow down the issues before I bring it in.  I use the bike to commute and don't want to be without it for months. Any suggestions would be welcome. I'll check the fuze this afternoon

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33 minutes ago, Rollos said:

I am under the 4 year Honda care I bought with the bike last year but I'd love to narrow down the issues before I bring it in.  I use the bike to commute and don't want to be without it for months. Any suggestions would be welcome. I'll check the fuze this afternoon

Ok. If the fuse is good. Then with a meter check the ground supplied to the fan relay by the ECU which should be there at around the indicated 225degF. If it's a relay issue this can be easily swapped with the headlight relay (headlight relay is only for Hi Beam operation). Also it shouldn't be a hard task to unplug the fan relay and jumper the power feed for the fan to check its operation.

Cheers.

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Fuse looks good so I'll have to check the relay

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So I ended up riding to work and the temp went into the 240s in heavy traffic. The fan is running. I'm not sure why it didn't run this morning. 

So here's the situation:

Fan runs

Plenty of coolant.

Still overheating to the point when the idiot light comes on

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Sounds like your thermostat isn't opening all the way so you're not getting full coolant flow. That or your water pump isn't working properly. There's no reason it should go that high if your fan is working.

 

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19 hours ago, Rollos said:

I wish the fan ran with the engine off. Any reason why it's wired not to?

It does as long as it’s within it’s working parameters, the ignition is on and killswitch  in run position.

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9 hours ago, Rollos said:

Checked coolant this morning and added about 6 ounces to bring it up to the fill line. I let the bike warm up then rev'd to 5k RPM to bring the temp up to 225. No fan. 230. No fan. 240. No fan. Turned bike off. 

 

I have Gremlins. The fan was working fine yesterday. 

 

I booked an appointment at my local Honda for a warranty repair in two weeks. I'll be riding it like it's an airhead until then. 

 

So now I'm thinking thermostat, and fan wiring since the fan still turns so probably not a seized fan motor.

Hi Rollos. Why didn't the fan come on????. Is it possible your bike isn't overheating! 

The ECT Engine Coolant Temp sensor has two outputs. One to the instrument panel the other to the ECM.

It seems odd you may have faulty thermostat But why did your fan not come on per your test?

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3 hours ago, Grum said:

Hi Rollos. Why didn't the fan come on????. Is it possible your bike isn't overheating! 

The ECT Engine Coolant Temp sensor has two outputs. One to the instrument panel the other to the ECM.

It seems odd you may have faulty thermostat But why did your fan not come on per your test?

I might have an intermittent short in the fan relay wiring but I haven't had a chance to check yet. That's the only explanation I can think of.

 

The bike definitely feels like it's overheating regardless of what the temp sensor and instrument panel are telling me. I believe it when it's reading 250° because I'm roasting sitting on it. My butt temp sensor is in full agreement there..

 

I've pulled over a few times in the past two weeks when the instrument panel read +235 and threw it in neutral. Every time I've done that the fan was spinning but the temp kept climbing on the instrument panel. I end up hitting the kill switch around 245 and waiting for 15 minutes...

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Hi Rollos.

It seems like your Thermostat is not fully opening as it should be by 203degF (or something horrendous with your water pump). So without full coolant flow your cooling fan may not be sufficient to cool your bike. However what disturbs me a bit is the fact you did a test all the way up to 240degF (115degC) and your fan did not come on!

 

Why not just for the hell of it swap your Fan Relay with the Headlight Relay, they are right next to each on the R/H side of your bike. You will need to carefully remove the R/H Rear Cowl.

You can then also have a good look at the Relay wiring, run some voltage checks and check continuity of the ECM wire Gr/Bu from A23 (ECM Black Plug) to the Relay Base.

If your are really keen you could test the Fan, by removing the Fan Relay and place a jumper link between Bi/Bu wire and one of the Bu/O wires with Ignition to OFF, the jumpering of these wires should start your fan up every time you make the link. WARNING - Just DON'T jumper anything to the Gr/Bu wire as this goes to your ECM.

Do you have the wiring diagram, and service manual? 

Good Luck.

 

VFR_Relays001.jpg

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13 hours ago, Rollos said:

Fuse looks good so I'll have to check the relay

Put in a new/another one to rule out "looked good but was not". Donot ask why I know.... :goofy:

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So it sounds to me like you have checked the coolant level in the expansion bottle, but have you checked the coolant level in the radiator ? If you bike really gets that hot, you should see a change in the level in the expansion tank as it heats up it expels excess coolant to that tank then sucks it back in when it cools again. The 8th gen is prone to radiator puncture from road debris I minor crack high up will lose coolant & fail to suck any from the expansion tank !

 

1. So I’d advise, check coolant level in the radiator at the fill point pressure cap.

2. Check the pressure cap seal is clean & seating correctly. I’d advise you make a note of which way round it is & replace it in the opposite direction. By this I mean look at the writing on it & replace with the writing in the other direction.

2. Run bike static & you should NOT feel heat in the rad until it’s close to operating temp when the thermostat will open & allow coolant to circulate.

3. Whilst the bike is warming, look at the front rads for any sign of leakage or steam.

4. Warm it long enough to cycle the fan 6 times, as in fan on off cycles. If this does not happen then there is a fault in the system somewhere. 

5. Wait for bike to cool fully, then repeat #1 coolant check.

 

Water cooled engines only fail to cool for a couple of reasons, namely lack of coolant or lack of flow, provided their fans work.

 

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