Hydraulic Diagnosis

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maxgreenwood
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Hydraulic Diagnosis

Post by maxgreenwood » Sun Jun 15, 2014 11:13 pm

So the 19trs engine is a bit more healthy after a coolant flush any running nicely with nice new clean oil.

I got rid of some sediment in the lhm tank and cleaned the filters.

Whenever I re-bleed the hydraulic system, the tick cycle time seems healthy and normal, but as soon as I use the brakes it returns to cycling every second or two, pressurising with long hisses even above 1000rpm.

I have replaced the regulator and fdv for good ones.
I have checked the returns using the CitroenBX DIY pages, and one of them has a slight steady trickle, another a drip and the other two next to zero returning. So I'm suspecting something to do with the brakes.

Before I condemn the brake valve behind the bulkhead/brake pedal, could partially seized brakes cause this? The brakes are not very good, takes a lot of pedal pressure for a BX. Maybe the caliper pistons are gunged up.

Any thoughts/insight would be much appreciated

Max
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon

Tinkley
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Re: Hydraulic Diagnosis

Post by Tinkley » Mon Jun 16, 2014 12:15 pm

Accumulator sphere? How old is that?. Strange things can happen when this gets low on pressure. Not sure if it can affect brakes, but certainly the system can develop little leaks, like at the green Y junctions because of this.

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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood » Mon Jun 16, 2014 1:15 pm

the accumulator is very good, up to 1 min between ticks on the donor car. I think i have eliminated all other possibilities. The brake valve looks like a relatively easy swap if i can just get at it behind the 19 engine.

Someone please correct me before i go barreling in there :)
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon

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MULLEY
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Re: Hydraulic Diagnosis

Post by MULLEY » Mon Jun 16, 2014 3:01 pm

Daft question, is it possible that your broke hoses are letting in some air? Otherwise it's possible that the brake doesuer has a fault?
2002 C5 2.0 HDI Estate - Remapped - It goes better
2011 Mini Cooper D Clubman - it does over 60mpg
1992 TZD Turbo - SORN - slowly getting there
1991 Gti 16V - Blaze is back on the road since 2008
1990 Gti 8Valve SOLD - looks like it's been scrapped
2002 Mini Cooper S - SOLD - i miss this car
1992 TXD - Scrapped in March 2014

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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood » Mon Jun 16, 2014 3:46 pm

Wouldn't LHM be spurting everywhere on the feed to the brakes? I will check!
I think the Doseur valve is the one behind the pedal? I could swap that, bit of a faff.
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon

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MULLEY
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Re: Hydraulic Diagnosis

Post by MULLEY » Wed Jun 25, 2014 4:08 pm

I don't believe it would be spurting out if the holes are very small, they would be damp though when the brake pedal is depressed once pressure & heat cause the brake hoses to expand & let in air.
2002 C5 2.0 HDI Estate - Remapped - It goes better
2011 Mini Cooper D Clubman - it does over 60mpg
1992 TZD Turbo - SORN - slowly getting there
1991 Gti 16V - Blaze is back on the road since 2008
1990 Gti 8Valve SOLD - looks like it's been scrapped
2002 Mini Cooper S - SOLD - i miss this car
1992 TXD - Scrapped in March 2014

I'm not just a username, i'm also called Matthew.

Tinkley
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Re: Hydraulic Diagnosis

Post by Tinkley » Thu Jun 26, 2014 6:16 am

How old are the front brake flexy pipes?. They seem to last about 12-13 years. Also make sure the joint to the flexy is still tight. It is possible to have a weep there if not fully tight. Although I have not had a flexy completely split, I have changed them on 2 cars where outer 'cracking' was evident. Obviously I'd rather have brakes working on the pedal rather than rely on the handbrake.... :wink:

Definitely worth bleeding at least the front brakes as old fluid (after LHM change) remains in the latter part of the system unless this is done. My own experience leads me to believe this is well worth it and the brake 'feel' much improved. The colour of the old fluid will be quite different to the nice fresh green stuf so you will know when you have replenished the system.

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Re: Hydraulic Diagnosis

Post by MULLEY » Thu Jun 26, 2014 1:55 pm

I'm 100% with Tinkley regarding bleeding the brakes, it's usually brown/yellowy stuff that oozes out, keep it coming until you see lovely fresh green lhm coming out, then it's job done. My posts about the brake pipes are the flexy's that i was referring to.
2002 C5 2.0 HDI Estate - Remapped - It goes better
2011 Mini Cooper D Clubman - it does over 60mpg
1992 TZD Turbo - SORN - slowly getting there
1991 Gti 16V - Blaze is back on the road since 2008
1990 Gti 8Valve SOLD - looks like it's been scrapped
2002 Mini Cooper S - SOLD - i miss this car
1992 TXD - Scrapped in March 2014

I'm not just a username, i'm also called Matthew.

mds141
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Re: Hydraulic Diagnosis

Post by mds141 » Thu Jun 26, 2014 2:47 pm

Don't forget when bleeding the brakes, to start with the rear calipers, with some weight on the rear to account for the load sensing brake proportioning valve.
Mark Smith

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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood » Thu Jun 26, 2014 9:55 pm

Thanks guys I'll check out the brake lines when it's stopped raining! I seem to remember it is a bit damp round the wheel arches. Perhaps the discs are also coated in LHM! Certainly feels like that braking.
I bled them once before on a tzd - quite satisfying seeing the brown stuff come out.
The car sinks very fast front and back
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon

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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood » Thu Jun 26, 2014 10:59 pm

Well the flexis look ok on quick inspection altho need better light.

** I didn't mention the brake pedal hisses continuously when pressed even lightly.
I've had this sound for a second when stamping on it on BXs before but not like this. Something def up there- brake Doseur valve?
'92 16TXS (m), Dark metallic green, 74k
'90 16TZS (m), White, 86k
'89 19TRS auto, Olympic Blue, 133k
'88 Saab 900 8v Turbo (auto) 107k Red with Tan leather, lovely drive and well maintained.
'07 Hyundai Santa Fe 2.2 CRDi 85k (m). Practical family wagon