radiator hose life?

[daveson]

Hopefully the cap is ok and a bit of air is escaping at the hose clamps or the air hose connector.

The vacuum valve probably closes before the vacuum reduces to zero, so if the hose is only partially collapsed, that's probably ok (assuming the coolant level reduces after cooling down) But since you have new one's on the way, then it's good to replace them anyway.

[gard]

Pretty sure there is no leakage from the clamps or hoses, I did not mention above but I repeated the pressure tests while holding my finger over the overflow tube barb on the top of the filler cap neck, the pressure and vacuum levels held constant as long as I kept the barb sealed.

In my first post there is a photo of the radiator hose, it was partially flattened, not totally compressed. I will keep an eye on it the next couple of times I have it running. I guess an an experiment I could hook up the vacuum pump to the bike and measure how much vacuum it takes to flatten the radiator hose.

I have not ordered a new cap yet, not sure about that yet.

[daveson]

The first thing I thought when looking at the photo was, it looks like the hose has a twist in it. It's as if the hose clamp at the standpipe was tightened before the hose at the radiator was properly located.

That's some good tests you've done there.

Which book states how long the cap should retain its pressure?

[gard]

Thanks for your comment.

I found that info in the clymer book in the chapter 3 tuneup section, pg 55 cooling system inspection, "the cap must be able to sustain 16 psi for 6 seconds". With a quick look I did not find anything similar in the BMW shop manual pdf so perhaps that is a general instruction for radiator cap testers?

Thats interesting, I did not think about the possibility the radiator tube in my original post may be installed a little twisted, I did not remove the standpipe side when I replaced the cooling fan. The tubing returned to circular cross section when the cap was removed.

The existing overflow tubing seems to be a fairly soft degraded looking black unreinforced rubber, either original or dealer installed. The new tubing I bought and installed is also a relatively thin wall, easily crushed "blue silicone vacuum tubing" advertised for this purpose on ebay. I just noticed the photo in the Clymer book shows a heavier looking overflow tube, looks almost like a fuel line with the braded fabric outer layer. I think I will ride my bicycle to the nearest auto parts store and get something that has a stiffer wall that is listed for antifreeze. I am suspecting the tubing may be getting crushed someplace, it is not entirely clear to me where it should be routed along with all the other wires and tubes along the frame and under the tank.

Looking at the Clymer book they also recommend testing the cooling system by pressurizing it up to but not above 16 psi, it should hold the pressure for 6 seconds, I can do this with my homemade tester connected directly into the radiator hose after removing the filler neck.

 

[Kaos]

Well, you could test it as far as Iam aware the system runs on 1 bar == 15psi on boiling point.
You spoke of caps, the radiator cap or the filling cap?
The thermostat in the radiator should be opening at 0.1 bar or at temperature levels of 82, 85 or 87 Celcius depending.. there are 3 of them. The valve in that cap should be checked
If that malfunctions or is clogged, busted or in any other form not working it could cause the hose to end in a vacuum state.
Also my aftermarket hoses are pretty soft compared to the oems, not sure if that was a lifespan thing as they were installed when i couldnt even walk. But mine dont flatten.
At this point you als might want to check for a clogged system, do you recall the amount of coolant that you Drained from the bike?

Also bleu hoses. I feel somewhat betrayed.

[daveson]

Goodo thanks I see that in the book now, was just being lazy, only looked at the table.

The hose returns to normal shape with the cap removed, so if it returns to normal shape with instead, the overflow hose removed, then yep it could be the expansion tank hose collapsing. The expansion tank hose on mine is also soft and unreinforced, I spose that's strange, thinking about it now.

With the pressure test of the cap, sometimes flipping the gasket around helps.  If the hose seems soft, it might loose a bit of pressure as it expands, maybe wait a minute and repressurise it.

[daveson]

... I repeated the pressure tests while holding my finger over the overflow tube barb on the top of the filler cap neck, the pressure and vacuum levels held constant as long as I kept the barb sealed.

I think the results of this test shows that at least one of the valves in the cap is leaking. Hopefully a bit of a clean might help, yep probably a bit of wishful thinking.

[gard]

The crap blue silicone hose as well as the black one removed from the bike overflow tank and the radiator hose that goes behind the radiator all collapse with a couple of pumps on the hand vacuum pump, around 5" hg.  The overflow hoses are easily crushed between 2 fingers.

The auto parts stores both were unable to find 5/16 coolant, heater or radiator tubing. They do have what they call "vacuum tubing" which is a relatively stiff unreinforced rubber, about 1/2" OD, no way I can crush it between 2 fingers, vacuum has no visible effect on it. I bought a 3' long piece in a blister pack, only needed 2.5', $9.69,  Gates 27555. The website recommends it for only air or water or coolant overflow tanks. I consider this a win compared to the around $50 from BMW.

I pressure tested the coolant system as recommended by Clymer pg 55 using my homemade tester. It is supposed to hold 16 psi for 6 seconds. Initially I found a small leak at one radiator hose, tightened them all a little, now it holds 15 psi, I figure that is close enough for a 40 year old bike. Glad I found that small leak now instead of along the road with all the fairings installed.

The radiator cap has 2 flat face type gaskets that must seal to 2 different surfaces that are at different heights. I think this is not a great design practice, dimensional tolerances of the cap, neck or gaskets will result in one gasket working better than the other.  Redesigning it so one is a radial seal like a piston in a bore is outside of the scope. I removed the outer gasket to ensure good seal to the inner one. This reduced but did not eliminate the slow cap leakage in both the pressure and vacuum tests. So I am convinced one or both relief valves in the cap have a small leak. A new cap is on order.

I got distracted yesterday, someone showed up with a welding job on a dump truck. Today I intend to reinstall the gas tank with the cap I have, adjust the throttle bodies and go for a ride.

[gard]

Went for a nice ride, some state roads, secondary paved roads and a steep narrow single lane dirt road 2-up. No overheating problems and the radiator hose no longer collapses.  I think the issue was the degraded overflow tube along with some crap in the overflow tank. Still have the old radiator cap, a new one is on order.