Aux brake vac pump pulsing - help please.

[irishcarfan]

1999 S40 1.8 (Volvo unit) Auto Phase '1.5', 120k miles. Car is parked the last 6 months.

Timeline of events:
1. Changed radiator after crack appeared, and engine mounts.
2. Started car - hard brake pedal.
3. Found blown fuse for brake pump, replaced.
4. Noise from brake pump. I found it to be blowing not sucking.
5. No replacement available (older phase 1 black plastic unit)
6. Replaced with newer design (silver, upright), and new wiring harness
7. Brake pedal works but pulsating interior light suggested all not well
8. Found brake pump pulsing every half second.
9. Thought perhaps air leak or issue with booster, pipes etc.
10. Blocked off pipe to pump - no change.
11. Replaced pump switch and vac pipe - no change.
12. Haven't changed pump relay (located beside it)

That's where I am now. Any ideas what I should be checking? I presume whatever work I did caused the issue, though the pump blowing is suspicious.

Any idea what I should be checking? Is there anything related to the brakes that I wouldn't have thought of? I feel like I'm stupidly overlooking something obvious. Could ABS cause this issue?

There are no warning lights showing on the dashboard. Nothing found on OBD.

Observation - when I turn the ignition on (before starting), I can hear the pump come on for a few seconds. If I have my foot on the brake during this time, the pedal does not sink. Is that correct? It only sinks once the engine is started.

Any thoughts or random comments appreciated as I really have never had an issue like this before. Many thanks!

[canis]

Well, if it's a petrol engine then the vacuum assist only occurs when the engine is actually running, so feeling the brake pedal depress when you start the engine is normal. There's no pump, the vaccuum is created in the inlet manifold and carried to the brake servo by a pipe. I don't know what you mean by "hear the pump running" because there isn't a pump. You're probably hearing the fuel pump.

[irishcarfan]

Canis, I appreciate the response but you are mistaking the car for a manual. The automatic has an auxiliary brake pump hidden beneath the passenger wing - that is where the majority of the vacuum comes from and I have a feeling it's something to do with the VVT not allowing enough vacuum to be efficient hence the additional pump.

Many automatic cars have this be it Volvo or Saab.

For pig iron I have ordered a new relay, however, it's a radio interference type some of you 740/240 people might recognise, which I believe is related to the fuel injectors. I will report back if it makes a difference.