Hydraulic Diagnosis

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maxgreenwood
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Hydraulic Diagnosis

Post by maxgreenwood »

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 »

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 »

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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Re: Hydraulic Diagnosis

Post by MULLEY »

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 - Jasmine - Now SORN
2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - My daily
1991 Gti 16V - Blaze - crash damaged, will get repaired.
1990 Gti 8Valve SOLD - looks like it's been scrapped
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1992 TXD - Scrapped in March 2014
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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood »

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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My Cars: 1999 Xsara LX 2.0HDI (90) Hatch - Fern
2002 C5 2.0 HDI (110) Estate - Jasmine - SORN
2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - SORN
1992 TZD Turbo Estate - SORN
1991 Gti 16V - Blaze - crash damaged, will get repaired - SORN
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
1988 CX 25 GTI Turbo2 - SORN
1996 - AX Memphis 1.5D - Dream - SORN
x 8

Re: Hydraulic Diagnosis

Post by MULLEY »

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 - Jasmine - Now SORN
2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - My daily
1991 Gti 16V - Blaze - crash damaged, will get repaired.
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
1988 CX 25 GTI Turbo2 - SORN
1996 - AX Memphis 1.5D - Dream - SORN

I'm not just a username, i'm also called Matthew.
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Re: Hydraulic Diagnosis

Post by Tinkley »

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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2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - SORN
1992 TZD Turbo Estate - SORN
1991 Gti 16V - Blaze - crash damaged, will get repaired - SORN
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
1988 CX 25 GTI Turbo2 - SORN
1996 - AX Memphis 1.5D - Dream - SORN
x 8

Re: Hydraulic Diagnosis

Post by MULLEY »

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 - Jasmine - Now SORN
2011 Mini Cooper D Clubman - SOLD
2016 Mercedes A180D Sport - Auto refinement
1992 TZD Turbo - Bluebell - My daily
1991 Gti 16V - Blaze - crash damaged, will get repaired.
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
1988 CX 25 GTI Turbo2 - SORN
1996 - AX Memphis 1.5D - Dream - SORN

I'm not just a username, i'm also called Matthew.
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Re: Hydraulic Diagnosis

Post by mds141 »

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.
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maxgreenwood
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Re: Hydraulic Diagnosis

Post by maxgreenwood »

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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Location: Dublin, Ireland

Re: Hydraulic Diagnosis

Post by maxgreenwood »

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
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