Vacuum hose disconnected - why?

I was sorting out a problem on the brakes on the wife's Freelander (2005 TD4) when I came across a vacuum hose that had been disconnected and the end plugged with a screw. It must have been like this when I bought it as I haven't had to do any work on it until now. The hose in question presumably should have been connected as it is now in the picture below. I've taken it for a drive with the hose connected and I can't feel any difference at all in the way it drives. Why would this have been done in the first place?

EGR vac hose. You now have EGR you didn't with the hose off.

Why? Some blank oft the egr to stop the recirculation of gases to stop soot from the emissions getting back in and blocking it up. Blanking it oft gives a slightly better performance but doesn't give you the lower emissions output from the eggsource.

Thanks guys. I'll disconnect and plug it again then.

Hippo said:

Why? Some blank oft the egr to stop the recirculation of gases to stop soot from the emissions getting back in and blocking it up. Blanking it oft gives a slightly better performance but doesn't give you the lower emissions output from the eggsource.

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EGR is for the sole purpose of reducing Nox production. An incorrectly operating EGR can create smoke and excessive soot emissions. Providing the EGR is operating correctly there should be no noticeable difference in performance blocked or unblocked. Other than the placebo effect. The advantage is slightly less engine wear and deposit build up when it is disabled.

DefenderPilot said:

Thanks guys. I'll disconnect and plug it again then.

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Take care to plug the pipe carefully, the vacuum system also powers the brake servo, if it leaks then the braking efficiency goes to hell.

I cannot think that the EGR vac and brake vac are connected in any way. Very strange if they are.

wammers said:

EGR is for the sole purpose of reducing Nox production. An incorrectly operating EGR can create smoke and excessive soot emissions. Providing the EGR is operating correctly there should be no noticeable difference in performance blocked or unblocked. Other than the placebo effect. The advantage is slightly less engine wear and deposit build up when it is disabled.

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Yer but no but I always thought the recirculated mixture with partially un-burnt fool in it would have a lesser explosion (as it contains less fool) than the new mixture with new fool in it. Hence slightly more power with it disabled? I understand they don't recirculate much, but if there was enough fool in it to run propper then that would mean there's a lot of fool escaping via the eggsource, which would mean wasted power, if the eggsource gases contained a lot of fool which was potentially usable.

Hippo said:

Yer but no but I always thought the recirculated mixture with partially un-burnt fool in it would have a lesser explosion (as it contains less fool) than the new mixture with new fool in it. Hence slightly more power with it disabled? I understand they don't recirculate much, but if there was enough fool in it to run propper then that would mean there's a lot of fool escaping via the eggsource, which would mean wasted power, if the eggsource gases contained a lot of fool which was potentially usable.

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The same fuel is injected, just the air that is not needed for combustion is replaced by inert exhaust gas. Diesels always run with excess air.

wammers said:

I cannot think that the EGR vac and brake vac are connected in any way. Very strange if they are.

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There is only one vacuum pump creating the vacuum for the brake solenoid and EGR valve, if you follow the pipes from the EGR solenoid valves they are teed into the vacuum line running from the pump to the brake solenoid, if the vac pipes are not plugged correctly then they allow air in dropping the level of the vacuum. To be 100% sure you can buy a new pipe without the tee in it.
Plugged mine with plugs dipped in silicon and then put a cap on the outside

raywin said:

There is only one vacuum pump creating the vacuum for the brake solenoid and EGR valve, if you follow the pipes from the EGR solenoid valves they are teed into the vacuum line running from the pump to the brake solenoid, if the vac pipes are not plugged correctly then they allow air in dropping the level of the vacuum. To be 100% sure you can buy a new pipe without the tee in it.
Plugged mine with plugs dipped in silicon and then put a cap on the outside

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Ok strange set up if that is correct, brakes are usually autonomous. Bad design that. Maybe a seriously good idea to properly blank it in that case. Unplugging the EGR modulator valve would maybe a good idea. But maybe that may stress the ECU into a hissy fit.

I wondered about that so I just settled for plugging the vac line and putting it safe, one interesting thing I did later was to change my glow plugs, when I took the manifold off I could see why people blank the EGR, it was a mess inside, went to the local hot jet wash and gave it a good fettleing.
By the way glow plugs were duff but new ones made no difference.