Overheating VFR

I recently did some work on my 1998 bike, and after putting it back together I'm finding that it is overheating. During the maintenance I flushed the radiator fluid.

Looking at the forum for this type of problem I found a few potential solutions:
(1) bad thermostat
(2) bad radiator cap
(3) air bubbles in the cooling system

How can you determine which of these is causing a problem?



Here is some additional information on my particular problem. When changing the fluid, initially I only placed fluid in the reservoir and not the actual radiator. I then rode around my bike for about 10-15 minutes.

Towards the end of the ride the temperature gauge showed a reading of 270 degrees for about 5-20 minutes. I wasn't exactly sure what to do when it overheat, and finally ended turning the bike off to find that solved the problem.

Now when I ride the bike the fairings get warm, and also the frame metal next to the seat and below the gas tank. The fan turns on when the is at a still.

Any suggestions???

 

Was the bike cooling properly before the maintenance? You mention that you flushed the radiator. Did you refill it or just the reservoir? Did you check that the radiator is full after running the bike (and letting it cool down)?

 

270? That's an engine fryer. Your post sounds like you ran the bike dry with only fluid in the over flow? The whole system needs fluid.
The thermo could be bad as well as the cap due to the fact that they are over 10 years old.
to get all the bubbles out of the system after refilling, fill it up to the top of the filler cap. Run the bike for just a few minutes then burp the system again and fill as needed. One place air gets caught is at the highest point of the left radiator, right where the fan switch is. It can be burped by loosening it and allowing air to escape then retightening.

 

The bike did not have any cooling problems before the maintenance. Initially I did just fill the reservoir, and not the radiator.

Once I found that it was overheating, I discovered that the fluid was missing, and re-added.

Exactly what should be loosed to get the air bubbles out?

 

Just the filler cap. The fan switch at the top of the left radiator can be burped if the fan does not come on at 220 degrees.

 

Did you recheck the radiator after refilling it? Otherwise a lot of the water probably went to refilling the system and the radiator may still be only half full.

 

Proper procedure. Fill the radiator FIRST. The radiator has a pressure cap that allows the system to vent to the resevoir when; 1. Too much pressure builds in the radiator. 2. When heat causes thermal expansion of the coolant. Every effort is made to locate the radiator cap at the top of the system. When you run the engine the air will find its way to the top. As the coolant heats and expands it forces the air out the radiator cap and into the resevoir. The radiator overflow tube runs to the bottom of the resevoir below the level of the coolant, as the air from the radiator enters the resevoir it bubbles up through the coolant and exits the resevoir through the vent. Now here is the cool part. When you shut off the engine and the coolant begins to cool, the coolant shrinks and now draws only coolant back into the radiator. (Remember the overflow tube is below the level of the coolant.) Just like using a straw with your soda. You blow and make bubbles or you suck and draw in soda. When there is no air in the system the coolant flows back and forth in this same process. That's why you have warm and cold level in you resevoir, thermal expansion and contraction. This system makes the radiator self bleeding.

If you don't fill the the radiator first you have massive amounts of air in the system, a water pump can not pump air, only liquid. Overheating will occur.

Follow these steps.
1. Fill radiator with coolant.
2. Start the bike.
3. Run for a few minutes and top off coolant. Get the engine warm, you want to make sure the thermostat opens. (175/190 deg.F.) The coolant level should drop when it opens, top off coolant again.
4. Now close the radiator cap.
5. Next fill the resevoir to just below the upper or hot level. This should do it.
6. The next few days keep an eye on the resevoir and top off as necessary.

As Drewl says, if you find your fan does not come on at about 220, you probably have air at the top of the left radiator. Bleed air by loosening the fan switch until you see liquid and close it back up.

Sorry for the long explanation. It's always good to know how the system works.

Hope this helps.

Maggot

 

Over heating by blown head gasket

HI Stonee

I was just reading your post and although I have not done this on a bike I think I know why she is now overheating.

When you first removed the coolant you said you rode the bike for some considerable time before turning it off and it was very hot.

From this we can assume that the bike has definitely been ""Cooked"", I would suggest at least a blown head gasket causing the cooling system to have gases in it and thus overheat, if not further damage to the pistons and rings.

Too check this I would with the bike cold, top up the radiator and leave off the cap, start the bike and allow to idle for a few minutes, if you see bubbles or foaming then the head gasket is gone. Also check the oil for signs of water in the oil.

Make sure you put the cap back on once you are finished. If this is OK then you have been very lucky and you are probably only suffering a damaged radiator cap or thermostat.

You already have good advice on checking flow for the thermostat, the cap is another matter and for it's small price I would just replace it anyway.

Good luck with her, I hope she comes good.

 

this is a very helpful thread. my 98 is running hot, too. not 270 bad, but 233 is also too hot.

i ordered a new water pump, thermostat, and rad cap yesterday, hoping i can replace those parts and get some positive results.
i hadn't thought of bleeding the fan switch though. that's a good idea.
when i replace the thermostat, i'll have to move the throttle bodies out of the way, right? is there an easy way to do that?

also, the thermostat... is it a unique part, or can you pick it up at any auto parts store? if i can swing by and pick one up after work, i'm going to do that. i bought a used thermostat housing with pipes and all. i'm hoping that's a good thermo, but if i can pop a brand new one from autozone in there, that sounds better.

has anyone rigged up a second fan, on the right side? i'm thinking if i can wire up a second fan, and have both controlled by a switch on the handlebars, or just come on with the bike, as it does now, that should be one cool ride (hurr hurr hurr)

 

233 isn't too hot. If you hit that temp often may be a sign you need to refresh your cooling system like you're doing, but it doesn't indicate a huge issue nor a problem with how Honda cooled the bike (as everyone seems to think.)

250 is overheating by Honda's standard.

Honda designed the bike to run 170-220 before fans even kick on. Fans kick on at 220 means temps can rise as high as 240 on a real hot slow ride. No harm is being done.

 

that sounds good, but i still feel like my bike is overheating... i went for about a 30 minute ride yesterday, and when i got where i was going, the overflow tank was bubbling over, and i was losing a lot of coolant. by the time that i got home, the cooling system was empty. i filled up with fresh fluid, and it sounded like there was nothing in there at all.

even though i replaced my fan switch sensor, the fan turns on when i turn the bike on.

 

Radiator cap would be the first thing to swap. A bad cap will release at too low of a pressure and cause bubbling in the overflow at otherwise safe temperatures.

 

thank you, tanner! this has been very helpful. i'm ready to go for some long rides on this bike, lol, i just need it to stop showing me it's lesser liked character points.

 

thanks to this thread, i now understand that my vfr is not overheating.... but it is by far the hottest bike i have ever owned, out of 14 bikes. there is so much heat coming off the bike. any good ways to mitigate this? heat wrap on the headers, vtr fan, a dual fan? ceramic headers?

 

I love this thread... same bike, same problem. So, thanks everyone for the contribution. My gut is that it's the water-pump and it's just not moving the fluid around. Fan comes on, kicks off, fluid topped-off, reservoir topped. It could be the thermostat but, replacing that intimidates me (supposedly not accessible like a car's?) and last, I'm getting to 230's. Once to 250 degrees. It was Texas summer, two-stop stoplight and it ran up. at 250 is started flashing, then killed itself. After it cooled, it fired right back up. When I'm moving it will come down but, not quickly, which makes me think the water is staying stagnant and not getting to run across the radiators.

So, I guess... here is my question - (and thanks to everyone/anyone, in advance). How well would a 1998 run with the fairings off (for weeks)? They are SO time-consuming, I feel like I've spent the time on the repair, just removing and adding them. So, I'm hoping I could run with them off and replace the cap, then the water pump (because it's my gut)... Does it make the bike susceptible to rain or the radiators to knees or rocks or ????) Again, thank you all. Jellybean

 

I’m hoping its no big deal to run w/o fairings, because i plan to do this permanantly.
Have you checked to make sure that the overflow tank is half full when the bike is cold? That was my whole issue. I actually went through the trouble of prdering several replacement parts for my cooling system, and all i needed to do was add a little more coolant.

 

Thanks LooseNoose! I did check the resovoir first (while changing the oil). I was shy by a few drops but, not the answer. Next the right side and from the cap-down it was topped-off. Appreciate the response.

 

I hope that helped. It was very frustrating for me until i figured out the reservoir level was the cause of my overheating problems. I hope thats all you have to worry about.

 

My 2000 VFR overheated and started leaking antifreeze with a lot of smoke. I wanna try changing the thermostat and see of that resolves the problem.

 

The 5G and 6G need the fairings for the airflow to be sucked through the radiators.
The side fairing openings create a low pressure zone, while the rest of the fairing creates a high pressure zone at the front.
This forces the air to flow.
In traffic you have the fan to suck through the left radiator, so I think you could get away with it, but anywhere else you will have problems.
You can try it, but it definitely won’t be as efficient or even acceptable.