insertdisc4
Member Since: 22 Oct 2023
Location: CH
Posts: 11
  
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| Rock hard brakes! Ignition/start-up concern |
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Hi All,
Couldn't find anything when searching (maybe if it's a more common issue you can advise me the correct term to a search with).
Basically whenever I come to start my LR4 SDV6 2012 after a reasonable standstill time (12-24 hours), I find that the brake is really difficult to push-down (required before the ignition button will start the engine).
The only way I could describe it is that it seems like the brake fluid has slowly pressurized up to the max level during the standstill time.
I have to push harder than normal to allow the ignition interlock to recognise that the brake is engaged. Once the engine starts the pressure seems to normalise and the brake behaves as would be expected (with a more gradual, spongy response).
Interestingly I changed my front brakes around 6 months ago. This problem has only really started to appear in the last month - so I don't think it is related but mention it just in case.
If you know what I am describing and have advice, it would be very much appreciated - I get the impression this is going to lead to a major issue if not addressed.
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 10th Jul 2024 6:28 pm |
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KPTV8
Member Since: 05 Feb 2012
Location: Itinerant !! (Scotland/Donegal)
Posts: 192
 
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V.interesting !!
Similar symptoms have developed on my MY2009 D4 in recent weeks - no brake assist (i.e. brake pedal is hard at top of travel) after standing overnight, but brake assist resumes promptly after engine starts, and brakes then perform normally.
During same time frame (approx over recent fortnight) engine has increasingly become fairly rough from cold and while warming up, then settles down to normal when fully warm. While running rough, engine occasionally dies when approaching a junction or otherwise cruising to halt. Starts again without hesitation, but NOT NICE 'cos while engine is stopped there is no brake assist which is sometimes a bit panicky !! Until engine is fully warm I now have to keep revs up when approaching a junction or when coasting in order to be confident of effective braking - not a sustainable situation and as a precaution short term I'll have to start warming the engine fully before each journey.
Engine is petrol (V8 5L) and traditionally with older cars brake assist would be derived from inlet manifold vacuum feed to master cylinder, but in this D4 there's an engine-driven brake assist pump.
No obvious reason I can think to associate loss of brake assist with rough engine (other than after a stall), but can't help wondering why both symptoms have arrived in tandem ......
I'm about to switch to E5 fuel for a while as an experiment - car has been run on E10 since I bought it two years ago, engine has never misbehaved until now.
No relevant codes revealed via GAP IID device. No obvious fluid leaks, no smells or smoke or noise.
(Well, V.SLIGHT slow tick-tick from engine when idle & warm, bit like a slightly sticky or maladjusted tappet ...... not really noticeable unless I'm LOOKING for troubles !!).
My thanks to anyone reading this far  )))
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| 10th Jul 2024 7:47 pm |
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insertdisc4
Member Since: 22 Oct 2023
Location: CH
Posts: 11
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Firstly, V8 5l ..nice! I looked up a few of those but there were none local to me (quite rare in general I think), it's a solid engine I would imagine, especially when compared to the s/tdv6 (crankshaft concerns). Bet it moves when you want it to 
Interesting what you highlight, especially comparing across engine configurations . I haven't found much so far but will definitely will share anything I do. I have a mate who's a professional mechanic, going to check it out with him over the next few weeks. I need to do an oil change and some other things near-term so investigating this will be added to that list.
Thanks for the reply, keep me posted on anything you find as well!
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| 10th Jul 2024 9:10 pm |
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