Yet another overheating thread. - Fifth Generation VFR's

So I've been playing with my new (to me) '99 VFR and am having an issue that won't go away. I've seen numerous threads here and on the other forum about VFRs running hot, getting too hot, overheating, etc. Most of them seem to be due to faulty fans or switches, and it just doesn't seem to be the case here.

I did a coolant flush today, but this happened before in the same way. Basically, on a normal day, the bike will run ~180 to 200 on the highway and go up to 223 or so around the city, at which point the fans will bring it down. But in some cases, like today, when the temperature was warmer than it has been, or when i'm stuck in traffic in the tunnel, the bike will heat up past 230. The most I've seen it at is like 337, thinking that if it goes over 240, I'll shut it off and give it time to cool off.

Here's what's interesting to me about this: once it breaks 230, it STAYS that hot. At this point my already-too-loud exhaust sounds even louder and raspier, and the throttle response seems kinda off. Had a pillion tell me that the bike sounded strange today. If I make my way out to a highway for a stretch, it cools down but not much below 200, and once I slow down it jumps right back into the 230s. It continues behaving this way until it's completely cooled down, after which is seems to go back to normal range. This happened about 3 hours ago today. I just went downstairs and let the engine idle until the fan kicked in at 221 and promptly brought it back down to 209. So it's not like when there's a coolant leak or the fan switch is dead (or a head gasket) where it consistently overheats.

I was thinking of putting in a coolant additive, but it seems that it would just mask an ongoing problem. I also don't want to be ordering too many parts, tearing hair out, and finding myself replacing things that needn't be replaced. So the fan seems to come on OK at 220. Not the fan or the switch. I could follow someone's advice on some thread and get a Hawk fan which supposedly works better, but the stock fan seems to do just fine when all is controlled. So this leaves me with what I keep seeing referred to as a stuck sensor.

Could someone explain the regular symptoms of this issue and let me know whether I'm correct in suspecting that as a culprit? Is there anything else I could look in to? What exactly would I need to replace if that is indeed the problem?

Also, I've heard of people changing their fan switches to come on a lower temps (215 or so). How is this done?

Thanks :-)
Edited by Mazaev, 18 April 2012 - 08:47 AM.

this often happens after a coolant change, there´s air in the system.

to solve it take off the right hand fairing, remove the rad cap and start the bike on the side stand, let it warm up, so the rad is at the highest point. I´ve previously even put something under the front wheel to tip it over a touch more. Hold a rag over the opening and let the bike idle with the odd rev up to 4-5K. you can also squeeze the lower rad hoses a bit too. This forces any air out and is affectionately known as "burping". You should see air bubbles coming out of the coolant.

Bren

Don't forget that a stuck thermostat and/or faulty radiator cap can cause the same issues. As you stated in your post this issue was happening before you did the coolant flush. A partially stuck open thermostat will allow enough coolant flow to keep it cool for a while but after riding around for some time the heat continues to build. When you hit the highway you get enough air flow to help dissapate the heat and it cools down again. Slow down and it will come right back up. If you are sure you have the system "burped" well, I would check these 2 items next.

[image: View Post]Bren, on 18 April 2012 - 05:09 AM, said:

this often happens after a coolant change, there´s air in the system.

to solve it take off the right hand fairing, remove the rad cap and start the bike on the side stand, let it warm up, so the rad is at the highest point. I´ve previously even put something under the front wheel to tip it over a touch more. Hold a rag over the opening and let the bike idle with the odd rev up to 4-5K. you can also squeeze the lower rad hoses a bit too. This forces any air out and is affectionately known as "burping". You should see air bubbles coming out of the coolant.

Bren

+1


btw - I have the Hawk fan, and things kinda go like this..

Hawk fan - bike static, not moving - fail. Bike moving 5 -10 mph +....  pass.
Stock fan - bike static, marginal pass. Bike moving 5 - 10 mph .... fail.

Pick your poison....

Hmm, I sorta burped it, but didn't have it on the kickstand. Gonna give it another shot. Figure I can pick up a new radiator cap for a few bucks at Autozone and try that (the one on the bike does seem a bit brittle looking).

Does anyone know the part number for the thermostat (it's a '99)? Also, since replacing it seems like a pretty big job, is there anything else that should be replaced or upgraded in there once it's opened up? From what I can tell, the PO didn't really know what he was doing, and judging by the condition hydraulic fluids and air filter in the bike when I picked it up, not much maintenance at all was performed.

Well,  did the burp leaned over and a whole lot of air seemed to come out. Dumped in a bit of wetter water while at it and put on a new cap, so hoping for the best.

Sent from my DROIDX using Tapatalk

my 99 did something like this when I picked it up from the PO. coolant swap with a good burp did the trick. At the next change im adding a wetter Motul makes that has given me good results on various GL1800s and RC51s that were running hot. Any chance to test since your burp?

Isn't that a song by R.E.M.?

Everybody burps?

:laugh:

Yeah sounds like it had not been burped enough. Running it on the side stand seems to work best.

Your 99 shouldn't run all that hot especially compared to a Vtec, but 220 isn't really hot to Honda and why 220 is the set point for the fan to come on. 250 and above will start to flashing temp numbers.
Add some Engine Ice or water wetter and be sure your rad fins are clean and not damaged.

BR

Did about 180 miles 2-up with a 220lb passenger on it yesterday although it was a much cooler day and rained on the way bach. Filtering in heavy traffic, it would jump to 212 - 224 and then come back down. Moving at 20 - 40, it would generally stay above 210. On the way home going ~70, temps hovered around 170. It never got hot enough where it sounded raspy and acted jerky like it does over 230.

Basically, so far so good, but I'm gonna wait until I get really stuck in city traffic in hot weather before being able to relax. Frankly, this exact temperature display business is a total case of TMI.
Edited by Mazaev, 19 April 2012 - 03:41 PM.

This is helpful to me.  I'm having the same heat issues in that I didn't/don't understand why it's still over 200 at 50mph.  Basically if temps are over 55 degrees, it moves over 200 at the slightest provocation.

get a good burp on it, run a quality motorcycle coolant and it should improve. Mine will climb up over 210 if its really freaking hot out and im not moving but it comes right back down once I start going. Im using honda coolant now, switching to motul pro with mocool additive at my next swap.

My '98 was overheating so decided to do a coolant change.   Found a billion bugs, mud, and crap in the radiator fins from many years of riding!

Took radiators off, spent a *long* time carefully cleaning them, remounted them, and refilled with Engine Ice Coolant.

Life is way mo' bettah' now.   :tour:

Cheers!  E-Ticket

I the the PO had this issue... my 5th gen came with a simple switch that intercepts the wire to the left radiator. Flip it and the fan stays on... and the temps stay under 200° around town on an 85° day. Sometimes I forget and look down and it is showing 220° =\