Can I put 215/70/R15 winter tires from 2002 Montana on my 2003 Silhouette?

Yes , but you must use all 4 tires the same size

PUT A BREAKER BAR ON ENGINE CRANKSHAFT BOLT AND SEE IF YOU CAN GET THE ENGINE TO TURN OVER BY HAND,IF IT WONT TURN, SOUNDS LIKE SOMEONE SOLD YOU A EHICLE WITH A LOCKED UP ENGINE. GOOD LUCK!!!!1

You are ok with that. The numbers are
Xxx tire width
Xx is profile
R is rim size
Changing the profile is what throws speedometer off

Your tires are P185/65 R15 (CE) 195/65 R15 (S, LE)

Hi!

195(width in mm)/60(sidewall height in % of width) R15(rim diameter)

This means, a 195/60 R15 rides lower than a 195/65 R15 tire. Imagine how it would look like when you put these different tire sizes on one car. It can be done but the car will be unbalanced both mechanically and aesthetically. Remember, your car was not designed for different front and rear tire sizes unlike some sports cars.

A 2005 model will most like come standard with ABS as with most cars produced year 2001 onwards.
Just buy 1 tire size for your car. If you wish to change to another tire size, change all the tires.

Good luck!

1st check to see that all the lugnuts are tight. If that is not the problem you will have to go back to the tire shop and have the wheel balanced.

nope better to put on same size tire.because it will effect the abs brake system if one or two tires is smaller.

You can replace, but not mix. All the tires on the car needs to be the same size for traction control and ABS system. Having two different size tires on the car will cause problems. Just keep them all at the same size P215/60R15 or P205/65R15 only.

How do you know the thermostat is ok? If in doubt replace it. Water pumps are a even bigger what if. Did he do a radiator flush? Cooling system flush of the engine? Cooling fans come on at what temp and go off when? Replace the engine temperature sensor? 6 years old is bound to have sensors and such go bad.

No. You do NOT want to put 15" rims on this car. That will change a lot of things, and they all will be bad. The 15" rims will create problems with the ABS, and the ABS will not work properly.
Secondly, the speedometer will be way off, as the speedo is calibrated for the 16s. Third, and probably most important, your handling will be severly compromised. Please don't do the 15s.
Its not worth the problems that you will encounter.
a FixYa rating (4 blue diamonds) would be appreciated for my input.