Bleeding Coolant system in 2.5 Diesel.

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fergusminto
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Bleeding Coolant system in 2.5 Diesel.

Post by fergusminto » Thu Jul 29, 2021 10:40 am

Before I purchase a vacuum pump, just want to check if anyone has bled the cooling system using a vacuum pump and non-return valve via the bleed hose? Seems logical but does it work even when cold?
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g8dhe
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Re: Bleeding Coolant system in 2.5 Diesel.

Post by g8dhe » Thu Jul 29, 2021 11:21 am

Most of the vacuum systems I've seen referenced attach to the de-gassing tank and don't touch the bleed hose at all ?
See here for a typical system https://www.youtube.com/watch?v=OGuXoRV5xg4
Geoff
2001 Aero V6, AFT, full side conversion.
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fergusminto
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Joined: Mon Oct 03, 2011 1:47 pm
Location: Scottish Borders

Re: Bleeding Coolant system in 2.5 Diesel.

Post by fergusminto » Thu Jul 29, 2021 1:21 pm

Thanks for this. I don’t see how this works tbh. Obviously it does but can’t get my head around it. I could understand using pressure from my compressor to push coolant through the system from the radiator. What I am suggesting is sucking the coolant from the expansion tank through the system using the bleed tube and as a result “bleeding” the head which as it is higher than the expansion tank, tends to be where problems arise. I could also try pushing the coolant through the system from the expansion tank using the bleeding hose to let the air out. There must be an easier way than the tried and tested lengthy (and hot) method.
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g8dhe
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Re: Bleeding Coolant system in 2.5 Diesel.

Post by g8dhe » Thu Jul 29, 2021 1:42 pm

Ah think you need to think about this a bit more :-)

The compressor is used to create a vacuum using the Venturi effect ( https://en.wikipedia.org/wiki/Venturi_effect ) you use this after first draining the system and flushing any debris out first from the various parts.
The vacuum created by the venturi effect sucks out a lot of the air from the engine, and causes the pipes to collapse, when you have sufficient vacuum in the system and there isn't any leaks, then you introduce the new fresh coolant this replaces the vacuum in all parts of the system with the coolant. Job done.
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