Agila 1.2L auto 63 plate - Problem with brake fluid change

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Sat 5 Jul 2025 16:25
Agila 1.2L auto 63 plate - Problem with brake fluid change - AL Hughes
Im 76 and know little about my subject above.
Had brake fluid change. Day after brake light
Dashboard light flickered when I reversed onto road ( handbrake was off).
I called back head mechanic and he said that the fault was not his mechanics fault and checked it over.
His reply was “that the brake fluid levels were good. The reason the light flickered on the dash was that I was on a slope on my driveway and when I drove off my sloping driveway the sensor thought the fluid was empty”

What do you think? I think it is air in system as I have been parking the car on slopes for years with no problems and only one mechanic with a syringe did the job.
Advice please.
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Sat 5 Jul 2025 16:57
Agila 1.2L auto 63 plate - Problem with brake fluid change - bathtub tom

Have you checked the brake fluid level in the reservoir, There's probably a MAX and MIN marked on it?

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Sat 5 Jul 2025 22:48
Agila 1.2L auto 63 plate - Problem with brake fluid change - Andrew-T
The reason the light flickered on the dash was that I was on a slope on my driveway and when I drove off my sloping driveway the sensor thought the fluid was empty”

Surely if that explanation was correct it would have been happening before ? Perhaps the sensor float was misbehaving after reassembly ?

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Sun 6 Jul 2025 02:39
Agila 1.2L auto 63 plate - Problem with brake fluid change - edlithgow

A brake fluid change (as opposed to a full brake system flush and change, which is what really ought to be done) might just involve removing the old fluid in the reservoir, and then replacing it. A syringe might be used for that.

On the brake systems I have experience of (I don’t know your specific car) this would involve removing a brake fluid level sensor (a float piston with electrical contacts), integral with the brake fluid reservoir cap, and then putting it back when finished.

This could either stop or start a marginal sensor from working, but I’d guess it might be more likely to start working, which is perhaps why you are hearing from it now.

Air in the system would , I THINK, only be detected if it bubbled up into the reservoir, reducing its level, and was thus no longer in the system. This is probably unlikely, because air is not usually that easy to get out of the system, but not impossible

Most brake fluid reservoirs are translucent plastic so, unless very discoloured, you can visually check the fluid level from the outside against MAX and MIN marks without disturbing anything. A torch might help.

There is really no way to check on a mechanic without (a) understanding what they should be doing and (b) watching them do it (or NOT do it) and for many jobs once at that point its easier to just do it yourself

Edited by edlithgow on 06/07/2025 at 02:55

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Sun 6 Jul 2025 06:56
Agila 1.2L auto 63 plate - Problem with brake fluid change - gordonbennet

Yes you might well use a syringe to empty the fluid reservoir prior to actually changing the fluid in the system, you then immediately refill the reservoir without touching the brakes at all, but unless the system has been flushed through from every bleed valve at each caliper/cylinder the brake fluid has not be changed in either the ABS unit the calipers/cylinders or the pipewor, i doubt if the fluid was only replaced in the master cylinder without flushing/bleeding the system, if it was i'd be finding another workshop.

For your own safety and peace of mind check the brake fluid level now, if its not up to the full mark there is an issue, either it hasn't been refilled correctly after bleeding (annoying but so long as its above the minimum air should not have entered the system in the interim), or more concerning there could be a leak in the system, one possible leak source is a bleed valve not fully nipped up afterwards, to check for that possibility have a look behind each wheel for brake fluid...which tends to spread down and through the inevitable grime that builds up there making itself obvious.

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