Overheating

I have an 86 Maxim X with 26,000 miles on it. I have been the owner for a little over a year now. Over last winter I had the carbs out and did a basic run through and cleaning. When I put them back on, I noticed a coolant leak where the ports from the radiator enter the engine. I took it to a shop and they were able to get it sealed up again. However, now the bike is overheating. (Shooting coolant out of the vent hole in the plastic reservoir.)

I have tried flushing the radiator, thinking it might be plugged, but no luck.

Any thoughts or suggestions?

 

im not at all familiar with this bike/engine, but does it have a thermostat that could have been installed backwards?

 

Just jumping in on this because I have experienced the same issue with puking coolant from the reservoir. Oddly, this never happened until I recently did a complete flush. And it only seems to happen after I shut the bike off when riding hard...say above 5k on short trips. My temp gauge never indicates overheating.

 

I'd have to look at mine to be sure, but I THINK that the reservoir only gets fluid when the pressure in the system opens the relief in the rad cap.

The reservoir is obviously not designed to hold pressure and typically there is a vent on the metal body (under the cap) that allows "overflow" fluid from the radiator into the reservoir when it heats up. As it cools, the fluid contracts and it sucks the fluid from the reservoir back into the radiator.

The small hose from just under the radiator cap to the plastic reservoir should go almost to the bottom of the jug so as the coolant contracts it gets sucked back into the rad. The overflow hose should not stick into the reservoir very far (giving you an "operating range" indicated on the side of the jug.

You MIGHT have a bad radiator cap (or it's loose) that is not holding enough pressure in the engine and radiator.
OR it's just stuck.
OR the little reservoir is overfilled when cool. When it's cool, there should be a minimal amount of coolant in the little reservoir. If there is too much, it will probably continue to puke out until it purges enough out the overflow to give it enough expansion room.
I believe there are marks on the side of the jug to check.

If you're not overheating that's my guess.

Otherwise you might have other (more serious) problems.
If something is leaking internally you might be blowing exhaust into the coolant jacket BUT if that was the case you would also normally have some antifreeze leak into a piston when it's cool and the thing will smoke white smoke and smell like antifreeze. SO I doubt that's the problem.

 

Really helpful...thanks alot for your detailed response Mike. When I flushed the coolant I actually topped off that reservoir tank (per a post here). Sounds like that jug acts as more of an overflow to dump excess coolant and then it circulate back to the rad during low pressure/stress. I will drain most of it out tomorrow when cold and see what happens. Hopefully this helped the original poster too...

 

Thanks for the response.
My reservoir is filled to the right level when cool.

It is definitely overheating. The temperature gauge goes all the way up. Could this be a bad thermostat or water pump (if it has one)?
Seems like coolant is not flowing. But, when I flushed the radiator it seemed to flow through with no trouble.

It smells like coolant, but I thought that was probably from where it came out of the reservoir. I do not see white smoke.

 

if it has a thermostat installed backwards, wich is a very common mistake, it will never let enough coolant flow and it will overheat. if they resealed the t/stat housing, it is very possible it went in backwards.

 

I'm worried about the cooling on mine at the moment -- the temp spikes dramatically once I get off the freeway. Sometimes it climbs higher than I'd like while I'm *on* the freeway doing 65. Last night, drove home at 55, it was fine. I imagine the cooler air temp helped.

I was wondering how to tell if the water pump is indeed working or not, although the bit about the thermostat is an interesting idea. I'm tempted to dismiss it, because of the low mileage (less than 3000 so far), but I'll check the thermostat housing to see if it looks like it's been opened.

 

Do you know if your cooling fan is coming on Shaun? THe thermo didn't have to even be touched to be bad it could be stuck closed which will cause the enigne to overheat rather quickly. THe fan should kick on just as the needle hit the red maybe even a schoosh before it gets to the red. It is also possible I guess that you have an air pocket in the system as I assume you drained out hte water from the flush and then refilled? But I have never flushed mine as of yet. I know it is possible to get an air pocket on cars and snowmobiles if the correct procedures are not followed.

 

do these have plastic impellers? the plastic water pumps on other machines i work on crack apart and the engine starts to run hotter until it eventually begins overheating.

one way to see if the water pup is working is to take the hose that supplies the radiator with coolant off (not the return) and start the engine and give it a rev....coolant should spew all over.

 

The cooling fan is coming on. I hear it kick on when riding and it tends to stay on for a bit when I turn the bike off.

I'm starting to suspect the thermostat. I have changed these on other vehicles, never a motorcycle. Hard process? Anything I should know before I get into it? Do you agree this would be a good place to start?

 

it can't hurt to at lest inspect it if you have a cooking thermo you can pu tit suspended in a pot of water and heat it up to the specified temp(should be stamped on the stat) and see if it opens. You can also take it out and re-assemble and flush the sys. The cold water will not open the T stat there may be some crud in there that you couldn't flush out with the closed unit.

 

Hmmmm odd that the "fixed" the coolant leak, but now you are overheating.
There is little they could have done "wrong" that would cause the overheating I would THINK.

They SHOULD have simply replaced the O-rings on those tubes. IF they used some RTV silicone it's possible that the got some on the inside...but it would be difficult to imagine they got enough in there to cause a problem.

I would tend to suspect the thermostat as Zookie mentioned then.
Careful with the housing since it's aluminum and not terribly "heavy duty"

If it doesn't open all the way, AVOID the tempation to use a off-brand (like NAPA)...it might fit, but others have noticed that the opening in the NAPA version is about 25% less than the OEM part.

Yes, the water pump has plastic impeller blades, but they are on a solid disk and look very robust (doubt they would break)

Last year a guy on the micaspeak email list had a cooling problem from HELL>> he tried everything on his X. He finally found the problem after hours of trying everything we could think of.
The water pump is gear driven off the shaft that also spins the alternator rotor. I can't remember if it was the "driving" gear on the rotor shaft or the "driven" gear on the pump, BUT one of them has a spacer behind it. Well at the end of the day the spacer was missing and the gear would "float" in and out occasionally driving the pump, and occasionally leaving is not turning. As you can imagine the teeth on the gears were slowly getting worn off and it continued to get worse.
You can get a peak at the gears by pulling the little access cover on the right side off. (part number 38 on the parts diagram)...the little cover with (2) countersunk phillips head screws. Check to see if the retaining screw is on the "driving" gear, and I'd reach in there with a screw driver and see if the gears feel "secure" on the shafts (side to side). You could probably actually start it with that cover off to see them turn (or just spin it with the starter)....just pull the screwdriver out first!
The cover has an O-ring seal so it shouldn't require a new seal.

But the thermostat is a more likely suspect IMO