Cooling system/expansion tank question

[bengal taiga]

One of the weakest points on the stock E-9 and E-3 radiator seems to be the small port, onto which a hose is attached that connects to the expansion tank. The port is continuously subject to unnecessary stress because of the routing of the hose to the expansion tank - during routine maintenance involving the battery, alternator, oil filter etc. I am not saying that the hose is always in the way, it is just that it can be.

In my case, I just got though resoldering the hairline cracks around the little radiator outlet. To avoid any recurrence, I replaced most of the hose with copper tubing - without an apparent ill effects.

A few days ago, I noticed an E-3 at a gas station where the hose had been entirely eliminated (the port was apparently capped.) The owner claimed to know nothing about it and said the car runs "fine" and the work was performed by a radiator shop in another state.

The newer models seemed to have an improved design by rerouting the hose along the left hand fender. However, I never considered capping off the hose.

Has any one else done this?

How necessary is that hose to the proper functioning of the cooling system ?

Thanks in advance

 

[Malc]

The idea behind the small port at the expansion tank and in the top of the radiator is to try and eliminate any air that gets trapped there.
You can eliminate them if you want, but there is a chance that you would get air trapped in the top of the radiator when refilling the system as the bleed screw on the thermostat housing is lower than the top of the radiator.
A bleed valve or plug at the top of the radiator would help to overcome this problem, as would careful re-routing of the hose, ensuring there are no "U" bends in it
Malc

 

[bengal taiga]

Re expansion tank and followup re fan selection

Thanks for not chiding me in asking a fairly self evident answer. I was staring at a not dissimilar expansion tank from a 64 Ford Thunderbird when posting. I suppose another answer is mounting the radiator/pressure relief cap at the highest point of the cooling system. I guess it should be noted that some of the later 7 series and perhaps other models, use a tiny plastic tube (it closely resembles a vacuum line) for the same purpose. This leads me to a distantly related and somewhat trivial question: the best fans/fan blade design.

From memory, the coupe was originally equipped with a mechanical "drum brake" fan clutch with 5 fat blades. Upgrading to a viscous clutch first offered an 8 bladed "rigid" red fan. That later begot a black 11- bladed affair. All of these fans worked fine, although I have assumed that the newer fan blades are the more efficient of the lot.

Yesterday, I was approached by someone driving a very nice 500CS Benz, who opened his trunk and asked me or confirm if he had the correct fan for a 3.0Si. He wanted to compare the fan with mine. I obliged. However, I noticed that 5 of the 11 blades had varying degrees of triangular molded cut-outs toward hub of the blade. The blade appeared to have a 2004 or 05 stamping date. Except for the "cut-outs," the fan seemed identical to mine.

I have no intention of swapping fan blades to be fashionable, and it may be that BMW has already further modified the current offering. However, it would be a very simple matter to copy the modifications. I surmise the irregular "cut out" modifications are for sound reduction (not unlike irregular tread designs).

Has anyone on board actually compared the new with the even newer fan offerings? Opinion?

Thanks.

 

[Malc]

You are correct regarding the fans. My engine has the original 5 bladed one with irregular spaced blades and a worn out clutch :roll:
A lot of folk "upgrade" to a 9 blade fan with a more up to date viscous coupling, as found on the E28 However the way they mount to the water pump is different, well in my case, thus you cannot put a "new" fan assembly on an "old" water pump and vice versa.
Now the newer viscous coupled fans also wear out and or the heat sensitive strip siezes so beware of any second hand ones you don't know the history of.
Bluemax is a good authority on the cooling systems on the E9 and I would suggest you have a troll through his posts on the mattter
CFN
Malc