Coolant system problem on a Rev 800

[JROD]

So here's what's going on. I over heated my sled in Lincoln last weekend on hardpack trails and by overheated, I mean I stopped when the temp hit 180 degrees. No problems, let it cool down, made it back to town.

First ride since then which was today, riding on decent trails up the ridge and it starts to get a little warm 160-170 degrees. We get to the riding area and I'm finally able to get out into some deep snow. Now here's the kicker...

Temp never drops. My rails and front and rear cooler are all hot and getting plenty of snow kicked up on them so the pump must be working fine. I don't have any coolant leaking anywhere and have a full bottle. The problem is, when I take the cap off the coolant tank I have little to no pressure in the system which most definitely has something to do with the overheating.

Short of checking every single piece and part in the cooling system, I don't know where to start. Does anyone have any ideas or heard of anything like this before?

 

[milehighassassin]

What I would do or not do:

-Not take the cap off of a hot motor.
-Get some ice scratchers right away

Check the coolant temperature sender

Did you give it enough time? If your exchangers are hot, and you are getting snow on them, everything should cool down.

ARE YOU SURE that your pump is working? The could still be hot if your pump is not working.

Oh, I would replace your thermostat as well.

 

[JROD]

I've been working on sleds for a lot of years and I understand the ramifications of pulling a cap off of a hot engine but the point I was making was there is no pressure in the coolant system. This is a problem as it should have 13lbs of pressure.

I also have scratchers but that is also not the point. Scratchers make no difference when I'm overheating in a foot of fresh powder on a decent 4 feet of base.

Coolant temp sensor is checked and working fine.

You are right though where if my exchangers are hot and I'm getting plenty of snow on them, everything should cool down. But it's not, that's the problem

First thing I'm going to check here soon is the pump but I've got plenty of flow into the reservoir and with both heat exchangers getting hot, I couldn't see the possibility of a pump not working. How could my exchangers be getting hot if my pump isn't working?

Thermostat could also be an issue if it was stuck and short circuiting the flow to the coolers and passing the majority of the water back to the engine rather than the coolers.

BUT ALL THINGS CONSIDERED HERE, WHY WON'T THE SYSTEM BUILD ANY KIND OF PRESSURE AND NOT HAVE ANY SUBSTANTIAL LEAKS.

FEEL FREE TO CORRECT ME IF I'M WRONG ON ANY OF MY ABOVE STATEMENTS.

 

[NITROSKIDUDE]

i HAVE NEVER HAD A COOLANT PROBLEM ON A SLED. bUT WITH A CAR i HAVE IT TURNED OUT IT WAS THE THERMOSTAT BEIN STUCK OPEN, nOW WHAT WAS HAPPENIN WAS THAT THERE WAS NEVER ANy TIME (opps not yellin) for the water to cool down, The consistant flow would continue to heat. Now when the thermostat closes, it slows the water movment in the coolers long enough to coolit and the opens to cool the motor, i would change your stat or get the themostat deleat kit.

 

[milehighassassin]

You might also check the cap, or get a new one. It might be bleeding pressure off.


The coolers could still get hot. The coolant will naturally circulate itself with convection. As the water warms up it will naturally flow up. Cooler coolant will flow down.

 

[eddy]

Overheating

We had this exact problem. The cap is not keeping pressure even though the thermostat works fine. In this situation the engine will overheat and the expansion bottle will be full. Also bleed the system after you replace the coolant, cap and thermostat.

 

[JROD]

Thanks for all the input. I just finished putting a coolant system tester on it and it held 15 lbs for 20 minutes and the cap tested out fine. But the tester uses a bladder to seal off the top of the bottle and therefore negates testing the actual rim of the bottle where the cap actually seals to the bottle.

I never even thought of how convection could move the water but I suppose that's an idea. But even with that, a guy would think the system would still pressure up.

Sounds like I better get a new bottle, coolant cap, and thermostat coming. You would think a good dealer would stock that sort of thing... but not around here.

 

[milehighassassin]

Check e-bay. The Doo price for both the bottle and the cap are INSANE. I found one on e-bay but ended up buying one from a wrecked sled on doo-talk for easily 1/4 the price. Probably arrived in the same amount of time.

I thought about the convection circulation because I have a coolant heater hooked up to my car (VW TDI). It doesn't have a pump to circulate the coolant, but moves it with convection. It mounts to the lowest part of the cooling system.