Isuzu Trooper Owners Club UK™

[jbaker]

I'm trying to understand how the cooling system works. I have no workshop manual and the translated from Japanese owners' manual is confusing me. Can anyone enlighten a novice?

The owner's manual calls the translucent tank at the side of the radiator the "radiator reserve tank". I've been calling it an "expansion tank". Page 8-18 says...

[Google]

[suzu]

So the level should go up and down depending on the temperature?

Is this how it works... It's difficult to see any other pipes connecting with the tank, so I think the pipe from the radiator filler neck is the only way for coolant to get into the reserve tank. To do that it must get past a rubber seal in the radiator cap, which I guess happens when the pressure in the radiator rises high enough. So the level in the reserve tank rises as the engine heats up & coolant is pushed into it. As the engine cools the coolant in the radiator sucks the excess coolant back into the radiator from the reserve tank, so the level in the tank falls.


this is correct so far



This seems to make sense to me and explains why you fill to different levels depending on the temperature. So... why does the owners' manual suggest elsewhere that you ALWAYS fill the reserve tank to the max mark? On p 8-19 & 20 it says how to refill the system. Action 10 says check the water level in the radiator filler neck after the engine has cooled. Then action 11 says "Fill the coolant in the reservoir tank to the MAX line." But the engine is cold at this point, so filling to max would be over-filling.


in theory it should always be on the max mark when cold, this is so there is always plenty of water in the tank should it start to use a bit, and they expect you to check the level regularly so you should notice it dropping and get any problems sorted. but they all seem to use the water in this tank and there are no leaks. as long as when the engine is cold and the rad is full then as long as the water is on the max then don't worry if it does drop the just top it up it's when it keeps emptying itself and the rad is empty then you got problems.



Also the warning box on p 8-18/19 about being scalded says the "radiator reserve tank (radiator) contains hot fluid which is under pressure". Mine can't be at a very high pressure, because my reserve tank is open to the air via the overflow spout on the lid. When I take the lid off & the engine is hot there is no 'pop' as pressure is released - I think it operates at low pressure.

there is no pressure in the expansion bottle as you pointed out it's open to atmosphere and is there to collect the water thats get pushed out due to expansion.


By the way, the short "overflow spout" on the lid of my reserve tank has no pipe connected to it - shouldn't it? If it overflows the coolant is sprayed all over the top of the air filter box. I could fit a rubber pipe with the other end dangling down beside the radiator.

thats correct it's a *beep* if they fill the cooling system with diesel it does go everywhere and smells for ages a rubber pipe would be a good idea in case it does go wrong.