Just wanted to report that I tried Shelboss' coolant fix using a Honda 600 filler to make the coolant tank into a non-pressurized reservoir. I've been running it in very hot weather and heavy traffic for a few days now and it's working GREAT! It was very easy to do too.

Sam

Thx f sharing!

Could someone explain how the pressurized circuit can be changed to a non-pressurized circuit?
Can the reservoir remain the same or has to be changed (to a CBR 600 one)?
Ciao

probably a bit of a "suck eggs" response...but...

The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). The pressure increases the boiling temperature of water or coolant. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. I don't know what it is on the Paso; probably similar? The boiling point of water increases when the water is placed under pressure. When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system.

Normally - for most cars - when the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank.

with the Paso setup all you get is a slightly higher temperature engine operation without too much coolant loss; once you get over about 120 C [depending on coolant type] you lose it out the drain onto the road...

The "car" arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

All the Paso system does is a "total loss" setup; the filler reservoir will suck air back in when it cools down. At least the air is located up high and is not likely to re-enter the cooling system.

A "no pressure" system will operate OK if (and only if) there is sufficient coolant, efficient cooling and expansion space to cope with the hotter engine. If there's lots of coolant available you're OK. The lack of pressure in the system means the coolant will be able to boil at it's boiling point...so expansion due to temperature will be earlier...if you have expansion space this isn't so bad...

The problem I see is getting excess air (bubbles) in the system and potential cooling inefficiency where it's needed (at the heads and barrels)...so an associated issue might be the engine temp sensor might not read as high as it should be (i.e.: if the engine is really hot but the supply coolant is not).

I think Francesco's question is simpler than that Laddie. Yes you use the existing Paso expansion tank. The radiator outlet and cap that you add seals pressure prior to the expansion tank so the tanks doesn't need to. They fail because of this pressure and heat cycling, while most other cars and bikes do not pressurize the tanks. They just use them for overflow. This modification and pictures are in the tech section, once you do it you will wonder what Ducati was thinking

That's a good price, I think the filler neck without cap is $35 new from Honda. Hey Sam, do you ever get up to Moto Market in Acton for Euro cruise nights on Thursdays?
Art

Small world, I get up there 3-4 times a season, either with the 907IE or the Norton Commando. Maybe see you there next week if the rain ever lets up!

I originally recommended taking the rubber washer out of the stock coolant reservoir cap to release pressure once this modification is done. I had some coolant splash out the overflow hose so I think a better solution is to cut a slit in the part of the washer that is under the plastic release valve holding it in place. The slit should not extend to the outer seating surface. That way the inner valve that normally lets air back in the reservoir will release pressure but not leak out the overflow.

Does anyone have any pics of the modifications?

It's in the 907IE tech section, but applies to all Paso's
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