vicsvinyl

Took my A8 for a test drive after tons of work and it overheated at idle in my driveway and shut itself off. When it cooled a bit it did that fast idle, no rev up trick.
I was able to drive it out and turn around to put back in garage. After it cooled completely it started up normally.
Is there some special way to refill coolant in the 4.2l ? Did I have an air pocket? I've had it running up to normal temp according to gauge multiple times before this test drive.
Is the belted eng. fan supposed to freewheel in both directions? There were no codes or warning symbols.
Should the electric fan be running or do both fans only run for AC?

Homegrown-MN

Hiya,
I cannot be certain my input will help you, but my experience refilling the D2 A8 ('01 with AUX) coolant after a rebuild was rather simple.

The water pump should move in both directions easily. If you feel any binding, there is a problem internally. What about your thermostat? Are you sure it works?

Refill procedure that I used and then drove 1600 miles without incident. It may not be Bentley method, but is similar.

1) Close drain on bottom of radiator (if open)
2) open ports on both hose running to heater core; hoses in front of driver firewall (put some rags under hoses to catch fluid that will spill)
3) fill coolant via reservoir up to the very top and give it time for fluid to settle in block and radiator
4) start car briefly and let coolant level in reservoir drop as fluid circulates
5) shut off car before coolant gets hot
6) check coolant level in reservoir and top off as necessary
7) start car again and run with heater on HIGH FAN and hottest setting
8) when coolant starts to flow (without a lot of foam/bubble) from heater core hoses, then close both
9) Shut down, let engine cool and check coolant level...and for any leaks

I like to put a sheet of cardboard box to see if there are leaks, but dont put it down until after you've finished adding coolant to reservoir/purged heater core.

vicsvinyl

Tried it with a coolant pressure kit. Got coolant out of both heater hoses but no luck. Maybe need to use a hose on heater vents and push more fluid into a container.
New thermostat / doesn't mean it can't be bad though. Lot o damn work tho just to find out.
Don't think it's a head gasket.

Dr. A8

I had the same problem and it kept acting like a non-functioning thermostat. I could tell that coolant wasn't flowing into the radiator because it was cold to the touch. I had just done timing and thermostat. I finally took off the upper radiator hose and found a rag in the radiator inlet. I had put it in the upper radiator hose to keep coolant from dripping out while working on it. I felt stupid for sure. This was also after I swapped in another new thermostat and it kept doing this. I even bought an aftermarket thermostat and compared it to the stock replacement. The aftermarket units don't open up nearly as much and I wouldn't trust them to allow enough coolant flow.

4Driver4

Off topic, but don't feel so bad. When I was a junior tech at VW a thousand years ago, I "lost" a rag when doing a head gasket...coulda sworn I had four, but now only three. Hmmmm.
I'm sure you know where this is going: I popped out the spark plugs and found the rag in one of the cylinder bores where I had placed it (along with three others) to keep crap off the top of the pistons while I cleaned up the gasket surface on the block.
Took me about half an hour to pull that rag shred by shred through the spark plug hole using a coat hanger and a pair of needle nosed pliers.
To this day I have no idea how I was stupid enough to leave the rag behind but yet smart enough to figure it out before I tried to fire up the engine.

vicsvinyl

LOL I did put a rag in the top hose inlet at that pipe on the side of bank 1. It kept drippin forever.. Sure I took it out or did I.

Dr. A8

Thanks, I don't feel that bad but at the time it was pretty frustrating. It was one of the few time s I decided to take it to a mechanic. They told me the electric fan was bad. I went down and got it lol. It was winter and the aux electric cooling fan should never be needed when it's cold out. I pulled the car off their property and jumped the connector and the fan turned on. Took it home and figured it out.

rbjones17

By the way, the mechanically driven fan should free wheel in both directions but it should be very stiff to turn and should immediately stop moving when you stop applying pressure to it. If it spins freely and continues after you stop applying pressure then the fan clutch is worn out and it won't cool your car properly in the absence of the electric aux fan which normally won't run unless you are running the AC or unless the temp exceeds a certain temp.

Dr. A8

Any updates? I hope you got it figured out.

vicsvinyl

Had a bad coolant temp sensor connector. No cam codes after I disconnected it. Replaced sensor and connector. Power washed the radiator again.
It ran good for about 25 min. then shut itself down at around 224 degree's.
This time I checked water pump housing also. It was at 224 also and just the top hose area too. Rest of the 80% of the radiator is normal.
I think Blauparts sent me a bad thermostat in the timing kit.
Really dread taking it all apart again.
I'll pull the top hose today also just incase