Coolant System

[m3rk]

Hi guys,

just a quick question, as you look in the engine bay is it normal for the left bottom hose to be cool/cold and the top right hose to be hot?
i had the water pump and thermostat replaced at 82k 5months ago as a precaution when i bought the car, currently on 84k.
the temp gauge also doesn't go above the normal 12 o'clock position
car in question is a 2001 330ci

thanks,

mark

[Paul]

Hi guys,

just a quick question, as you look in the engine bay is it normal for the left bottom hose to be cool/cold and the top right hose to be hot?
i had the water pump and thermostat replaced at 82k 5months ago as a precaution when i bought the car, currently on 84k.
the temp gauge also doesn't go above the normal 12 o'clock position
car in question is a 2001 330ci

thanks,

mark

Mark,

What do you mean by cool/cold?  The lower hose is going to be cooler than the upper hose, but they both should heat up after normal driving.  However, I'd expect the upper one to be hotter.  If your temperature gage goes quickly to the 12 o'clock position and stays there while driving/idling, I'd say everything is fine.  If you are worried, I'd bleed the coolant system to make sure.

Paul

[m3rk]

Hi Paul,

Thank you for your reply.

The vehicle had been running for no more than 15 mins at the most, hadn't been driven any distance - just around the corner from my house to the petrol station and back again. temperature gauge built up to the normal 12 o'clock position and didn't move over that point whilst sat at idle or when driven, when i got back on the driveway i checked the top hose which was hot then checked the lower hose which to me felt cold in comparison, no sign (to me anyway) of warmth. However it is cold in the uk at the moment, perhaps i should run it right up to temp on a long drive so the fan kicks in just to make sure there are no problems?

Mark

[Paul]

Mark,

I checked out my upper and lower radiator piping and they both were warm (the upper was the hotter of the two).  This was after a 30 minute drive, so the car was nice and warm.  Take it for a longer drive and check it out.  If it's staying in the normal position, I wouldn't be too worried, especially after replacing them 5 months ago.  My last thermostat lasted about 5 years.

[m3rk]

Hi guys,

Just thought i would update this issue i have been having. After further checks and looker deeper at the problem i have found a split in the middle of the radiator and what appears to be fresh drips at the bottom drivers side of the radiator. Also having removed the fan cowling etc and see more of the radiator, at the bottom it has standard to bend slightly, not sure whether this is to pressure or not 

Have ordered this morning new top and bottom hoses, level sensor, expansion tank, fresh coolant and a new radiator.

Mark

[Paul]

Glad to hear you found a smoking gun.  Good luck with the repairs!  Let us know how it goes!

[dangdude]

The vehicle had been running for no more than 15 mins at the most, hadn't been driven any distance.

Sounds like your thermostat was just barely open.  Assuming no leaks (loss of pressure), the thermostat is almost never all the way open--it cracks open as needed to regulate flow to the radiator and keep the engine at the right temp.  "Full open" should never be needed, even at high rev racetrack conditions where lots of heat is generated.

So, imho after 15 minutes the flow was minimal.  But you also found leaks.  When you have leaks, the pressure needed to keep the coolant a liquid at operating temp is gone, so the coolant can boil and cause air pockets. Air pockets can stop the water from flowing, since the air pocket can buffer and absorb the pressure from the pump like a sponge in a low flow situation.

Again imho, your radiator bend and leak in the center might be due to damage (hitting something).  The leak on the driver's side is most likely a split expansion tank--for some reason they tend to go at 75-100k miles.

Your new parts and approach is the correct fix.  Paul has a REALLY good DIY here which I'm sure you found.  The job is very easy.  Next time I'll be using a funnel when removing the block water jacket bolt... yech!