99 Yamaha Mountain Max Overheating - Snowmobile Forum: Your #1 Snowmobile Forum

Gerk · 02-10-2013, 05:40 PM

Hey guys, new to the site. Looks like there are some very knowledgeable people on here. Hopefully someone can help me out.

So I did a little research and found a little bit of info on this but not sure I have an answer.

My 99 Mountain Max triple 700 is overheating. The light came on and I opened the hood. Coolant was escaping from the fill cap in the hose. I got stranded at top of mountain for a while yesterday as the hose eventually shot off of the filler and left me with no coolant at all.
Long story short, I got it home.

Today I did some checking on it after some research.
I took the cap off and started it. The coolant does move but constantly. When I rev it it seems to move better. I thought I was able to take impellor off my list but Im not sure. I did a bleeding of the system which i was told to just remove the screw on top of the thermostat put the cap on and run it. I would have guessed it was harder than that but you guys can hopefully tell me what I did wrong.
I was hoping that would do the trick but after a quick trip around, the temp light came on again.
I know I am riding on hard pack. I have snow kickers and the exchangers were barely warm.
Please help if you can and sorry for the long post.

Thanks all

**RJ Gleason** · 02-11-2013, 06:33 AM

Are the exchangers getting warm?
To burp the system, you have to get the front end up higher than the rear exchanger.

Gerk · 02-11-2013, 09:25 AM

Ya know I did read that and forgot to lift the front.
So I need to remove the screw on top of thermostat and lift the front while its running? Anything else? Can I park it on a steeper hill?

The heat exchangers are warm but nowhere near hot.

**RJ Gleason** · 02-11-2013, 03:48 PM

If they get warm, then the coolant is circulating through them.
It still wouldn't hurt to burp it just to make sure that all the air is out of the system.

mmsrx · 02-11-2013, 06:44 PM

Are you sure the thermostat is working properly? It mabey starting to stick.

yamadad4 · 02-11-2013, 07:37 PM

more than likely no stat in that sled.

what been known to happen to those is the brass gear on the impellor shaft slips on the crankshaft. the brass gear is a pressed fit and expands at a different rate than the steel shaft it on and when it warms up, can slip on the shaft and not operate the impellor properly.

if all else checks out and you have the air removed from the system, consider this as a possible source. sled will usually work well cooling wise at low engine temps, but begin to overheat as the brass gear heats up and slips. hope that made sense.

Gerk · 02-11-2013, 08:23 PM

Theres a thermostat housing so I am assuming there is a thermostat. That was my first thought was problem with thermostat.
I am dreading that its an impellor.
Has anyone had to change this? If so, was it a long difficult process?

yamadad4 · 02-11-2013, 10:30 PM

although it looks like a t-stat housing, i dont believe the 99 700 mtn maxes actually had a t-stat.

as mentioned, check all the possibilities first. if the problem continues after the sled warms up a bit, most likely the impeller shaft gear is the culprit.

not that difficult of a job for the most part, i find it easier with the engine removed, but it can be done with the engine in place.

you can test the gear on the shaft by heating it and see if it rotates. the fix is to replace the entire impeller shaft as an assembly with the gear(only way to can get it).

Gerk · 02-12-2013, 05:14 PM

Well Ive done some more tests.
The impellor seems to be the problem.
I went out and ran it again. The heat exchangers were warm at the start are when the temp light went on the right heat exchanger was same temp as earlier and left one was as cold as the snow.
Am I correct to assume that it would be the impellor?

If so, I would greatly appreciate some tips to fix/replace what I need.

Thanks again all

yamadad4 · 02-12-2013, 08:28 PM

think of it more as the impeller shaft and the brass gear i mentioned previously. to me the impeller is the plastic fin that spins the coolant through the system and usually doesnt have any issues unless something hard went through.

theres a drain bolt, a cover, gasket, and then you can see the impeller. from there you need to work the shaft out. the shaft will come out with a bearing or two attached, an oil seal, along with the brass gear. the inner most bearing may stay in place. sometimes the shaft will come right out, sometimes your in for a fight.

you need to start by removing the pump cover and see whats going on under there.

Gerk · 02-12-2013, 09:26 PM

Quote:

Originally Posted by yamadad4

think of it more as the impeller shaft and the brass gear i mentioned previously. to me the impeller is the plastic fin that spins the coolant through the system and usually doesnt have any issues unless something hard went through.

theres a drain bolt, a cover, gasket, and then you can see the impeller. from there you need to work the shaft out. the shaft will come out with a bearing or two attached, an oil seal, along with the brass gear. the inner most bearing may stay in place. sometimes the shaft will come right out, sometimes your in for a fight.

you need to start by removing the pump cover and see whats going on under there.

Im sure its tough to say, but from what you read were my issues and results, to you does it sound like my problem?

yamadad4 · 02-12-2013, 10:42 PM

if it didnt sound like your problem, i wouldnt have taken the time to inform you about the problems associated with the brass gear on the drive shaft for the impeller(it actually drives the impeller via the crankshaft) nor would have i given you a guideline as to how to get to it and check it out.

take the info for whats its worth. it wasnt a guess as to your issue, but most likely a pinpoint accurate diagnosis, if not a point in the right direction.

Gerk · 02-21-2013, 10:01 PM

OK, so I decided not to deal with it myself. I gave it to my mechanic and he did find the impellor crank to be bad. He didn't want to spend my money fixing it as he said it would cost way too much to fix. Is that true? I don't really want to sell the sled as a parts sled because of that. I didn't think that it would cost much but he claimed the labor hours and parts would come to a large total.
What do you all think?
The sled runs great besides the fact that it heats up quickly.

yamadad4 · 02-21-2013, 10:19 PM

all associated parts would total under $150. in good hands, its less than an hour to swap things out, even less if you can prep things for your mechanic, like having the pipe and y-pipe removed and offering clear access to the pump housing. i assume you simply dropped the sled off as a whole.

worst case, depending on shop rates, 2 hrs at $100 per, plus parts, your at or around the $350 mark. add a gallon of coolant to be on the safe side and your cost can increase almost $15.

if he has already deemed the shaft to be bad, he's already in and you should be waiting for parts, not having your mechanic trying to scare tactic you, so half the labor is already accounted for. theres only two ways that i know of to test the shaft. could be some other issues, but highly unlikely.

whats your sled worth? i think someones blowing some smoke, find a more suitable mechanic.

Gerk · 02-21-2013, 10:25 PM

Thanks for the quick reply.

Thats what I thought.
Hes a polaris guy so he new about as much as me once he started.

I dropped it off complete and now I have a disassembled engine(not completely, but water pump is open, carbs are off, etc...).
I have all parts in a box - Yippee.

yamadad4 · 02-22-2013, 08:29 AM

might as well get to know your sled a little better. jump on in there and see if you can tackle this yourself. plenty of guidance around here.

Gerk · 02-22-2013, 05:03 PM

Quote:

Originally Posted by yamadad4

might as well get to know your sled a little better. jump on in there and see if you can tackle this yourself. plenty of guidance around here.

Thank you very much for the help.
I would love the help but Im not sure where to start. I can take pics or whatever you need. I am not a mechanic, but I'm also not an idiot. Ive just never done Snowmobiles before

yamadad4 · 02-22-2013, 07:35 PM

dont think of it as a snowmobile, think of it as a water cooled 2 stroke engine.

from what i have read, sounds like your almost ready to pull the impeller shaft, if the pipe and pump housing are off. not sure why the carbs were removed, but we can save that for later.

a picture of the current status on the engine may help me to save you some steps. for the most part, if you have some basic tools, your set. the only specialty item needed would be a good set of snap ring pliers. about $10 on the average at the auto parts stores, sears, etc.

basically your going to remove the impeller, then by removing a snap ring, a seal or two, the driveshaft for the impeller will come out. from there its simply reinstalling new parts, reseal, add coolant, bleed the air out and ride.

if you can turn a wrench, you have this this one in the bag. your worst hurdle will be figuring out what goes where out of that box of parts. hopefully someone labeled things or paid attention on the tear down.