94 Formula overheating - Snowmobile Forum: Your #1 Snowmobile Forum

kaw550 · 01-07-2005, 05:34 PM

I just rebuilt the top end on a 94 Ski Doo Formula ST (470cc)

I got the sled from a coworker who blew a piston on one side. I was told
the carb was clogged.

I honed the cylinders and put in new rings. Missing was the thermostat and
temp sending unit. I bought them new from a local dealer.

The temp light seems to go on shortly after the engine is running. I
checked the sending unit and the circuit is closed. It does appear that
coolant is flowing through the reservoir tank. Any ideas? The plugs were
dry.

My exciter did the same thing but the cooling system needed to be bled. The
ski doo manual says nothing about bleeding the system.

I am pretty sure I put the thermostat in the correct way.

**smallengineguy** · 01-07-2005, 05:48 PM

Did you bleed it? Air sometimes gets trapped in the heat exchangers and the front end needs to be lifted up to get rid of it.

kaw550 · 01-07-2005, 06:49 PM

I did fill it, ran it then let it cool, I then losened the "bleed" screws and let some coolant out

The manual ses to remove the screw and fill with coolant until it starts to leak. Then put them back in and fill the overflow.

I will try raising the front and trying it again. I dread having to drain the coolant to check the themostat or sensor.

**smallengineguy** · 01-07-2005, 08:43 PM

The rear of the sled sits higher than the front and air bubbles can get trapped at the back of the sled. Raising it up can get the air to move frontwards and out. Most thermostats are installed with the domed part UP.

kaw550 · 01-07-2005, 08:48 PM

Hvae you ever hear of a new thermostat or sensor being bad?

Is there an easy way to drain the coolant?

**smallengineguy** · 01-07-2005, 10:12 PM

You can boil a thermostat in water to test it. You shouldn't have to drain the coolant, just remove the top hose and thermostat housing itself.

kaw550 · 01-08-2005, 05:29 PM

I took our the themostat and ran the sled. The temp light still came on

I also put the thermometer in the coolant tank, it only read 130.

I then cooked the thermostat and sending unit.

The thermostat opened at 135 and the sending unit closed at 150.

When I first start the sled the temp light is on.
I used my voltage meter to check the sending unit. Cold there was some resistance. I assume there should be none???

I drove it around the the back yard and tested the sending unit. This time the circuit was definetly closed (overheated)

Could it be a bad sending unit (it is brand new)? There are no specks for testing it in the manual.

Now I am afraid

fr0st · 01-09-2005, 04:26 PM

your best would be a REAL temp gauge... i installed on on my 89 pantera.. costs 30$ at canadian tire and is a mecanical type.. the only wires on it are for the back light.

i made a hole between the speedo and tach and put it there.. they have ALL the right fittings to make it fit on your engine.

that way, you will know whats REALLY going on, and you will also know when the sled is ready after warm up.

i prefer this that a stupid light to tellme my engine is cooked... allt hats missing is that little bell when the chicken is ready in the oven.

fr0st

kaw550 · 01-09-2005, 07:15 PM

DO THEY HAVE A WEB SITE?

I am in Mass with no plans on going to Canada in the near future.

**smallengineguy** · 01-09-2005, 10:00 PM

You have an eBay account? Easy to find there. Same temp guage used from 1987 through 1996 I think...