XJ750 Maxim-X Water-cooled - Coolant spraying from overflow

Have had small amounts of coolant spraying from the reservoir tank (white flecks on gas tank and valve cover) usually at highway speeds. Now that I've stored the bike, I took the radiator off (not plugged), checked the thermostat (opens when in boiling water, closes when cooled), checked the fan switch (working), and am wondering what else to check. The radiator cap looks original and I know if they get weak, hot coolant could be forced out the cap and into the reservoir, hence, pressured fluid spraying out as I drive. Is there any way to check the rad cap? If not, are these still available new (Chacal will likely know), or are there alternative caps that'll fit? Is there any other thing that could cause the problem I have described? I assume the water pump is fine as there are no weird noises coming from that side of the engine. When I had the bike apart last winter, I checked the water pump and it was snug and turned when the engine was turned over. The spraying problem didn't start until about August, and continued until I quit riding in October.

 

Fans?
H2O Pump?
Wrong Coolant blend. (Coolant/Water ratio).

 

i work with radiator on cars,havent worked on many bikes
but usally that either sounds like
the thermosatic opens but not fully ,or
small leak in head gasket(small), or radiator cap not applying enough pressure inside,or if its the water its not circulating, or blocked radiator.
but hey how much is a thermo an a cap cost.but this is just my opinion. :wink: :wink:

 

Rick:
Water pump turns with the engine, fan turns on when 12 v applied to the plug, and coolant mixture is under 50/50.

3784rider:
The thermostat opens as full as it physically can, no leaks, radiator clear. Aounds like I'll be looking for a new cap, hopefully that will fix it. Oh yeah the hoses are all good, nothing collapsed or blocked.

 

You can more accurately check the thermostat using a cooking thermometer and watch it as it cools, note the temp where it starts to close, and finishes closing.

You could take your cap to an auto parts store and look at Toyota and Honda caps. Get the correct pressure rating.

 

It might be a leaky head gasket. The cap would likely not be able to hold against cylinder pressure.

You may be able to sniff the radiator and see if this is it. If you smell gas or burnt gas it's probably head gasket.

Pray its the radiator cap.


Loren

 

I don't think it's the head gasket as the coolant was green with no oily stuff floating in the containers. I also just sniffed the radiator (thank God nobody was watching) and it smells like coolant. Gonna do the cap first, then the thermostat if it still has problems. Thanks for all the feedback guys!

 

Check the seals around the end tanks. There could be a minor leak in there that just collects when not moving, but blows out when air hits it.

 

Re: XJ750 Maxim-X Water-cooled - Coolant spraying from overf

when i im talking about head gasket may leak its leaking from the piston into the water pockets.it could be the start of a very small leak.see i you can borrow a radiator leak tester,one that fits in were the cap goes an has a pump an guage.((when it runs does little air bubbles come up with the cap off)) :wink:

 

If a Cylinder leaks into the Water Jacket, ... the result is usually the Coolant becoming superheated to such an extent that Engine overheats quite rapidly and "Boils-over" through the Overflow Tube or causes sufficient Pressure to make the Filler Cap vent.

 

Rick:

Would the fluid look different or smell funny? I suppose the only way to verify the gasket is to do a compression check right? I'm hoping this isn't the case and that it's just a weak cap...much easier to fix!

 

****UPDATE****

I replaced the Rad cap as I felt the spray was happening under pressure. When a cap gets weak, it allows fluid to escape under much less pressure than normal. Finally located one and after riding for the past month, there has not been any white flecks on the left side of the gas tank...problem solved. Wanted to post this just in case others run into a similar situation.

 

What cap did you get? Was it one for the bike or did you get a different type to replace it?

 

Found a used cap at a local bike shop that was in good condition. Got lucky I suppose as it could have been as bad as my original one.