Cooling woes

[AlfaMale]

Hi all.

Last week I embarked on a cooling system overhaul. All the rubber hoses were of unknown age, the radiator seemed to be weeping around the top tank (a ring of dried red coolant was present) and I was often getting temperature readings of 100 degrees (read through the nanocom)

I replaced radiator, rubber hoses, thermostat.

The car however seems to be getting hot worse than ever. Parked on the driveway it will get steadily hotter until I get too nervous and shut it down (usually around 105 degrees) and a quick spin around the block is nothing different.

The bottom of the thermostat is cold (top is hot) and bottom of rad is cold too.

I've tested the new thermostat, it opens in a pot on the stove.
I've put in a new viscous fan
I'm getting coolant return to the reservoir through the bleed line from the top of the radiator when I blip the throttle (none when at idling RPM) so I don't think there are any air locks.
With the engine running I can stop the viscous fan running by applying pressure on a block of foam along the top of the blades

Questions
Should I be getting coolant return to the reservoir at idle RPM?
How cold should the bottom of the radiator be?
When does the viscous fan normally kick in?
Is there anything I've missed?
What to do next?

[zzsteve]

Just did my radiator replacement.
I definitely get a trickle of coolant flow back into the expansion tank at idle.
Water pump impeller corroding away?
HTH
Steve '97 HSE

[PeterH]

Yes you should see collant coming back into the tank at idle when it is up to temp.
As Steve said, it could possibly be the water pump, but before you go there, are you sure you have bled all the air out of the cooling system properly?
If air remains in the system, it will cause overheating very quickly.
Raise the front of the vehicle a bit, take the expansion tank cap off and idle until it starts to get hot, turn it off, wait 20 mins, top up the expansion tank and do that 3 or 4 times.
Replace the cap and go for a drive, you will find the coolant level will drop a bit for a day or two as the remaining air comes out.

Failing that, check the hose that comes out of the bottom of the expansion tank for restricted flow, it goes through a metal pipe section that can get partially blocked.
I once had coolant coming out of the cap due to a blockage there, might be worth taking the hose off the bottom of the tank and give it a flush out with a hose, the other end goes into the thermostat.
I know it's a pain as you have to bleed the system of air again, but that did solve my problem once.
Hope that helps!
Cheers, Pete.

[Bazzle218]

Have you checked that the Radiator return (Bleed) line is not blocked at the radiator end. Have had the same thing happen on a 300 tdi . Baz