Overheating on hot days

Overheating occurs with my 1999 VFR800i when I'm in 1st or 2nd gear at high RPM on days over 85 degrees ambient and/or sitting at a stop idling. Replaced thermostat, made sure the fan was kicking in over 200 degrees, I think the radiators are in good condition, and coolant levels are good. It hit 240 degrees going through Deal’s Gap last August. I suspect fuel filter....it’s never been changed (32K miles on the clock) because no one can figure out how to get it out of the fuel tank. I also suspect the water pump. Any ideas? Thanks.

Lawrence Mayhew

 

It's not the water pump unless you see anti-freeze leaking out. It's not the fuel filter unless it's bogging down under heavy load. I'd flush the radiators out. They should flow water out just as fast as you can pour it in. Any chance you have an air bubble in the syslem?

 

Thank you for your advise. I will try flushing.
LM

 

was any coolant or coolant change do recently. if you have good flow and the fan works if you have straight coolant it could possibly be the cause. it has to have at least a 50/50 mix with water. the water is what absorbs the heat and carries it away. coolant itself is not a good heat transfer liquid. when u flush the coolant i would also run water through the cooling fans of rad. to make sure there is nothing clogging it up causing air to not flow freely through it.

 

In addition to whats been posted, check your radiator cap. If the system is not pressurizing it will overheat.

Action

 

a simple thing to improve temp regulation is to blow compressed air through the radiators them selves. It gets the dust and schmutz out from between the fins and lets air flow over them better. If you live in a dusty area, this can build up over time and clog a radiator.

 

sorry, i am jealous that you have warm days.

 

Hi ALL. Sorry if there's been a reply, or multiple posts about this, but I'm new to both this site and to VFRs. I have a 98 VFR800, with about 60K miles on it. I took it out last week, and on a hot day, the temperature started to climn way up to where the temp reading began to flash....I then noticed coolant spilling out of the reservoir and the fluid was boiling...as I heard it. Once I pushed it home, and cooled, I restarted to see if fan went on, and it did not, and once again the temp rises and hear boiling. I had not done any work on it prior to this. I have just ordered a thermostat, but since the fan does not turn, I suspect not that...maybe fan switch. Anyone have any ideas? I know there are no cracked or loose hoses, I checked and double checked...please help, I want to ride this again!!!! And, since I know changing the thermo stat on this is a pain in the rear, would like to hear more from the experienced riders...thanks!
Tino

 

Is your coolant low? I don't know about the fifth gen, but on my sixth gen when the coolant was low the fan sensor did not heat up enough to start it.

 

1.You can test the fan by hot wire and see if it work
2. if the fan fail replace, if not check the temp. sensor make sure it work.
3. Done all the maintenance as suggest above
4. Report back if you still have issue.

Good luck

 

A lot of times the cheesy bearings (plain sleeve bushing) in the fan will rust up and lock the shaft. Try to rotate it by hand and feel if it is stuck or crunchy.

 

Wow, you brought a thread back from the dead. Anyway, in my experience, the fan motors rarely go bad. The problem is usually the wire connection at the sensor in the bottom of the radiator. Clean the connection and she should be good as new.

 

Check your over flow hose. If it has a crack/hole in it, the rad will suck air when it needs coolant and then force other coolant out of the rad in to the reservoir bottle and your bike runs hot.

 

When doing a coolant change, I always flush the system with about 50/50 vinegar and distilled water, 2nd flush just with water, and finally add the 50/50 coolant.

 

Eddie :hss: good to see you drop by Sir :thumb:
I was just wonder what happen to all the old timer.

 

I actually think you have a bad radiator cap, and that it does not hold pressure (16 psi I think). Heat expands the coolant, and since there is no pressure, it boils over and overflows the coolant reservoir. Since it boils over, you have air in the system, and fan switch does not trigger, since it does not get hot enough.
It could also be stuck closed thermostat, but I would check out radiator cap and see if it holds the pressure. Local parts stores usually carry cooling system tester, and you can use this to test the cap as well.

 

Always suspect the rad cap FIRST if it's over 10 years old. Their spring can weaken, leaking pressure, or rubber seals may have cracked, leaking coolant and increasing temps.

Check the coolant levels with engine cold, should be slightly below the top filler. When hot, the level inside the overflow bottle should expand up to "1, so mark the height of the level before a ride, then compare level after riding.

Antifreeze goes bad if it hasn't been changed periodically.


Cap is also the easiest, quickest, and least messy thing to replace, so start there.