Boiling Coolant

[woody77]

'86 VFR700F, 18K miles

The bike has run pretty hot since I bought it, and now that summer's here, boy does it run warm. Today after riding home from work, steam was pouring out of the coolant overflow tube, and the exhaust was coated in a white film.

The level in the coolant bottle was down a ton, and I topped it off (but it wasn't empty).

Recently, when I finish riding, I'll hear the coolant in the return line gurgling, and today, with it steaming, I pulled the seat and sides and got to see it looking like a pan of water on a high, rolling boil inside the overflow container.

I'm using straight Engine Ice coolant, supposedly good to 256*F before boiling. The bike was hot, but not in the red zone.

At the bottom of the hill I live on, the temperate gauge was reading centered between H and L. The 700' climb in under a half mile that is my road (done in 1st gear at 4-5Krpm or so) had climbed it all the way to the fan turn-on point. This is normal for going up our road in warm weather.

I let the bike cool for a bit, and then restarted it once the boiling stopped. I then ran it parked at 4-5K for a bit, and watched the temp gauge climb back up from halfway to hot, over maybe 20 seconds or so. Coolant was boiling again.

Is this most likely air getting into the system? coolant shouldn't be boiling at these temperatures, unless the H and L are hotter than I thought. Anyone know what temperatures that they correspond to?

Once the bike cools off enough to touch it, I'm going to pull the fuel tank and see how the return line looks, and check it for cracks, etc.

About 500 miles ago I flushed the cooling system and put in the new coolant. It's been gurgly since then, so I might have screwed something up with that...

I did a full drain, both at the pump and the front drain plugs. I flushed the system with a vinegar radiator flush, flushed it with distilled water (twice), and then filled with Engine Ice Coolant.

While it's made gurgling noises before on hot shutdowns, the steam pouring out of the overflow tube is new.

Thanks for any help,
Aaron

[eddie cap]

It's difficult to troubleshoot over the computer; Probably when you flushed the cooling system and refilled with new stuff you never bled the system and therefore what you are hearing is the coolant boiling in the air pocket or pockets located in the top of the cylinder head. Another term for the condition that I believe you have is airbound. I am not sure if your 86 has bleeder screws or not. Cheek in the your shop manual and read the procedure for changing engine coolent. For you system to cool efficiently it needs to be full of coolant and not air. Also now may be a good time to check the operation of your thermostat,although there's a remote chance that the stat went bad at the same time you changed your coolant. Sounds like you are using the good stuff with" engine ice", so I can't guilt you into using something better. eddie

[woody77]

Thanks for the reply. I'll look for bleeder screws. And I found the problem, or at least, part of it.

The radiator was practially empty. The overflow bottle was low, but at the low mark on it, not empty at all. I filled the overflow bottle to the upper mark, and filled the radiator (a quart or so of coolant more went in), and restarted the bike, ran it to warm, and then turned it off, and let it cool until it stopped pulling from the overflow bottle, and repeated a few times.

Seems like the whole cycle is working right, but it's making more noise than I think it should. I think I'm going to pick up a new rad cap. It *is* the original cap, and I don't know if it had ever been off the bike or not... I bought the bike with 17K miles on in December, and for the last 15-20 years, it's had probably less than 2K miles put on it. Mostly it's just sat in a garage.

[eddievalleytrailer]

A bad radiator cap could cause your problem. A blown head gasket could do it as well. If the cap doesn't do the trick, check the compression.

[woody77]

just went out for a 20 mile or so ride (it's 10 miles round-trip just to the gas station).

It's chilly out now, upper 50s, for the first 5 miles, at a steady 50mph, the bike never warmed above a 1/4 off L. This is pretty good. I stopped, filled up the bike, and rode to the next town, and it was maybe a 1/3 of the way up. Stopped, dropped off a couple dvds at the video store, and then came back. It had finally warmed up enough that it was at half-way beteen H and L when I left the video store, and stayed around there all the way back home, until I hit our hill, where it went up to 2/3 of the way to H.

No gurgling heard until I got it home, no steam, either.

I'm definitely going to park it until I get a new rad cap for it, and then see what it does...

lesse, new grips, new rad cap, new R/R, new.... ::sigh:: the joys of owning a 21yo bike... But I like it anyway.

[eddie cap]

Woody 77, Hope you are getting closer to having the problem solved. I think overheating is my biggest worry when driving any vehicle, especially these
fussy little H2O cooled motorcycles. I recently purchased a new cap for my Y2K @ Honda, as I remember it cost about $30, so bring your money .

[DANIMAL]

Woody77,
I have an 86 vfr700F2 I don't think there are any bleed screws for the cooling sys. but the proper way to bleed the air from the coolant system according to Honda's service Manual is to run the bike with the radiator cap off untill the thermostat opens( let it sit at idle for 15 min). looking in the cap you will be able to see the coolant flowing. if you don't see the coolant flowing you could have a bad thermostat. snap the throttle open Rev it to 4000 to 6000 RPMs coolant level will surge do this several times. If there is air in the system the level will drop. top it off and do it a couple of more times till you get no drop in coolant level at Idle. shut bike off put on radiator cap insure that it seals good. then fill recovery bottle to the top line and your done.
i know this cause after i did a flush on mine the 21 yr old cap leaked and it was doing the same thing yours is. new cap $32.

[woody77]

I know the thermostat is working (to some degree) as the cooling fans cycle, and when they're running, it's obvious that they're helping, driving at speed also cools the bike down pretty quickly, depending on ambient temps... although that might just be air cooling of the engine, but I don't think so.

I'll head over to the Honda store later this week and get a cap. Hopefully it will be in stock. Also need to pick up some other stuff... always fun. :)

[DANIMAL]

9the coolant fan is operated by a thermostatic switch located on the end of the radiator. the coolant flow thermostat is in a housing attached to the coolant hoses it restricts flow until the engine warms up enough to allow a bimetallic spring to open the restrictor which allows the coolant to flow through the engine thus cooling it to the temperature which is set by the spring design. do you have a manual for your bike? if you do not you should get one Clymer and Haynes print fairly decent manuals for this model year. my Honda dealer does not want to work on my 21 yr old bike. some parts are no longer available(discontinued). their reasoning is that it could cost me a lot of money for them to find out what is wrong only to discover the part to that is broken has been discontinued. I get what parts I can from either www.bikeBandit.com or www.
Cheapcycle parts .com. The vagaries of owning an old bike. hope this helps . it is a great bike. mine is in my shop I am having to replace the header on the #4 cylinder. It cracked i took one off a parts bike I own. I bought it off ebay for $400. It had everything except the plastic body parts. good luck if you need anything PM me and I will be glad to help.
Dan
member of the 6th Gen Brotherhood and the first Gen Fatherhood

[eddievalleytrailer]

The fan on my '83 rarely comes on. It NEVER comes on while moving, only when at several red lights in a row. I rarely let it get hot enough to come on by itself, as I put a manual switch on it. I will usually turn it on when the guage gets to 1/2 way up, but it takes several lights in a row. If your cap is unable to hold the proper pressure, it won't circulate like it should, and will be prone to spew water out into the burp tank, until it overflows.

[woody77]

It was the radiator cap. The outer seal was cracked though in a few places. I rode the bike tonight with a new cap and topped off coolant levels. Shut down hot (unfortunately I kinda have to, living near the top of a small mtn), and not a sound from the cooling system as it drank coolant back from the overflow bottle.

No more gurgling as it pulled in air.

[eddievalleytrailer]

It was the radiator cap. The outer seal was cracked though in a few places. I rode the bike tonight with a new cap and topped off coolant levels. Shut down hot (unfortunately I kinda have to, living near the top of a small mtn), and not a sound from the cooling system as it drank coolant back from the overflow bottle.

No more gurgling as it pulled in air.

GREAT. I hope we were of some help. Glad it's running good again.

[woody77]

You guys definitely were. I went over the whole overflow bottle system with a fine-toother comb, double-checking each fitting and seal. I ordered the rad cap, just because it was old. After taking off the old, and actually inspecting it, the problem was obvious.