FJRiders.com

I just purchased a 2004 FJR about a month ago and summer has come early to Central Texas. Temps on my commute home are in the mid to high 90's with 30% humidity. Gave the bike a proper coolant change and for the most part, not had an issue. Except when stuck in stop and go traffic. My temp pretty much stays at 2 bars if moving, 3 to 4 bars in heavy traffic (Fan kicks on at the 4th bar). Some boil over has been noticed, is this the nature of these bikes? Have replaced the radiator cap, scrubbed the radiator and rinsed water from behind to get any debris that may stuck. No leaks noticed. Wondering if I should look at replacing the water pump & radiator.

Everything you said is perfectly normal. 2 bars when moving, 3 bars in stop and go, 4 bars the fan comes on. Except for the boil over part. Are you sure your not overfilling the reservoir? Their are hot & cold lines on it. When it cools down (overnight) is the coolant at or above the cold (lower) line?

+1. Being in N Tx and riding in the other parts of TX (and other SW states) in the summer, I've not had a boil over. Get moving again, find a place to take a break, pick a different route home, or retire like I did. All work to fix that pesky stop-and-go commuter problem.

Great info fellas! I reflushed the radiator and I'm trying some Honda HP coolant this time. I will keep an eye on the levels. If it continues, may take the radiator off and have it checked.

Took her out into the Texas Hill Country this past weekend for about a 300 mile run with the days temps in the mid 90's (Humidity about 30%). Combination of high revving twisties and 70mph+ long distance. Bike temp never got over 3 bars but had a boil over at lunch and once again when I got home. Second flush I have done to it, Replaced radiator cap. Is this the nature of the beast or should I look into replacing some bits (Rad & Waterpump)?

See my reply on one of the other forums (I think the UK one) where a copy of this was also posted.

Thank you Bounce. 40k miles on her. Do you believe its time to replace the water pump and radiator? Or do these bikes just run hot?

40k is nothing. No need to just replace them unless there's a failure. Do a proper diagnostics before just swapping out random (expensive) parts. Given the flushes you've done, it sounds more like an obstruction. Bent fins? Do you use a pressure washer? Plugged air flow from road crud? Internal obstruction (have it flow checked at a radiator shop)? In fact, if you're up for pulling the radiator, a shop can clean, repaint, and give it a clean bill of health for a lot less than a new radiator.

Wy does it boil over if it never shows an over heat? Wouldn't it show hot on the guage? Curious minds and stuff.

I looked at a car for a fella that was doing this. I couldn't find anything conclusive but suspected the radiator. The owner had an aftermarket radiator in it with a lifetime warranty. The shop that sold him the radiator put in a new one, end of his trouble.

I believe I found the culprit. Reversed reservoir hose at the radiator cap area. Will check back after a couple of rides.

So should have been overflowing into bottle but instead onto ground?

Name Etc. wrote:So should have been overflowing into bottle but instead onto ground?

My thought is the overflow bottle has a over flow on it.... so once it boils and fills the bottle it will over flow that bottle on to the ground.

I thought maybe the bottle was out of play because of a broken hose. So expansion that is normal went on the ground, and siphon back into radiator when it cools wasn't happening either leaving it low on coolant. It never did over heat right? Just expanded coolant onto the ground instead of catching it?

The bike never over heated (stayed at 2-3 bars), just the loss of coolant on every ride.

Name Etc. wrote:I thought maybe the bottle was out of play because of a broken hose. So expansion that is normal went on the ground, and siphon back into radiator when it cools wasn't happening either leaving it low on coolant. It never did over heat right? Just expanded coolant onto the ground instead of catching it?

The coolant will boil/boil over if the system isn't able to hold proper pressure.
Low pressure=low boiling point. If you've replaced your cap already, you might next look for a leak somewhere.
Even a small leak (gasket/hose clamp) will allow pressure to drop and can result in a boil-over.
...Just a thought.

Old Michael wrote:The coolant will boil/boil over if the system isn't able to hold proper pressure.
Low pressure=low boiling point. If you've replaced your cap already, you might next look for a leak somewhere.
Even a small leak (gasket/hose clamp) will allow pressure to drop and can result in a boil-over.
...Just a thought.

Michael is right....
A 50/50 mix of anti-freeze and water will boil at 226 degrees F. For every pound of pressure you can put on the system, you can raise the boiling point three degrees. If you're running a system with a 50/50 mix and ten pounds of pressure, the boiling point should be 256. Just below that temp, your engine should be pretty efficient.

After a couple of rides in 100+ degree weather with no further issues. Coolant rises and drops a little in the overflow bottle. Thank goodness it was something simple. Thanks forum gods.

Late to the party, but if the system doesn't hold pressure, it can boil over without showing high temps on the gauge. Normal operating temp is well above what water will boil at without being pressurized. I had a car with plastic tanks on the radiator, and one of the tanks turned out to be cracked. Would run around town but not get more than 10 miles at highway speed before boiling over.

Good to see yours is aright now.