Seeking help with rarely occurring issue with Citroen Dispatch van

[Dispatcher]

Dear All,

Newbie here - had a search through the forum but didn't see anything quite like this.

Am posting re: a rare and intermittent issue that I'm having with my 2018 Citroen Dispatch BHDi115 Enterprise van.

The issue has occurred 3 times to date, with there seemingly being no pattern to when it occurs.

The issue is that from a stationary position and with the engine running and 1st gear engaged, when I release the hand brake to pull away, forward movement does not occur as if the brakes were being applied. Then applying the throttle, the engine sounds rough/stressed as if it is straining to go, but can't. At this same time, the front of the vehicle appears to raise slightly on its front suspension. If I select reverse, again the van does not move, and in this scenario, the rear of the vehicle becomes raised, but this time on its rear suspension.

If I switch off the engine, wait 10 mins, and try again, everything is ok.

Thanks in advance for any help you can provide. I'm keen to give the garage some possibilities to explore as when they took it out, it inevitably did not occur and they have therefore not been able to address it.

Regards,
Richard

[Dormouse]

Hello. Welcome to the FCF. Does this occur only after the van has sat for a while with the hanbrake applied? Or, has it occurred at some point during a run when the handbrake is applied?

[Dispatcher]

Hi Dormouse,

Thank you for your reply.

It's the latter - i.e. it has occurred when I have been out and about - rather than, say, 1st thing in the morning while it's been parked up overnight.

All thoughts welcome!

Regards,
Richard

[Dormouse]

ok. Here goes! I assume the van runs ok otherwise. I assume you release the handbrake properly! I assume the brakes are otherwise ok. - please excuse the moronic assumptions. I think the servo for the brakes is just out of adjustment and is on the cusp of "self servoing". This is where the clearance between the servo rod and the brake pedal is too tight and as conditions heat up (normally) the clearance closes and keeps the servo "on". Ten minutes later it cools down and the clearance just opens enough to allow normal operation. Alternatively, (rarely) wear in the brake pedal system plus low clearance plus positional/slop issues allow this to occur randomly. Hope this makes sense. I have had this a few times, mainly on classic cars. It is not a common fault but it can occur and effectively locks the brakes on.

[Dormouse]

My next set of questions would have asked if you stayed near the sea or in an open area lashed with rain if this had occurred after leaving the van parked for a longish period. This would have lead to diagnosis of brake corrosion seizing pads and/or shoes. I have added this for any future readers. Hope this helps those of you out there as well as you, Dispatcher. Cheers

[Pablo]

When this happens is the brake pedal hard and right at the top or is it normal ie progressive?

It could be a non return valve in the master cylinder or (unlikely) the vent blocked in the cap. If the fluid is not returning to the reservoir the brakes will drag, the fluid will get hot and expand making the problem worse. As the fluid cools it will release the brakes

[Dormouse]

I need to clarify the tight clearance explanation. The part that is too tight is in fact the rod from the servo to the master cylinder piston. What happens in this case is that the rod holds the piston just over/past the feed hole from the reservoir so fluid cannot return back up - a tiny amount of travel is all that it takes. Rod cools and contracts a tiny amount - fluid can return to the reservoir and line pressure is not held on. The brakes feel entirely normal, they just don't release enough when you take your foot off the brake pedal. Some rods have a screwed tip to allow factory preset but many rods are solid one piece items. It is impossible to see the rod when everything is assembled so you cannot physically check for free play/clearance. The tell tale is that all 4 wheels are bound on. If it is only 1 wheel or 1 circuit you have problems in the hydraulic side not the servo side of the brakes. If the handbrake froze on for whatever reason then you would get the same feeling but only the handbraked wheels would be stuck. And since it only happens rarely and briefly, the chances of replicating it in the workshop is low so when it does happen again you need to quickly find out how many wheels are bound on and which ones. Clear?

[Pablo]

I had a similar situation many years ago when many cars didn't have servos as standard. It was a new vehicle prep and the customer requested a servo be fitted. I installed the kit and the pedal was rock hard. I had missed out 4 little spacers between the bulkhead and the servo.

Obviously not the issue in this case but related.

[Dormouse]

Yes Pablo, I agree. The careful setting up of the clearances from pedal to clevis, clevis through servo and then servo rod to master cylinder piston are all crucial. Then there are a whole range of things from air filter in the servo chamber, blocked master cylinder vent, dirt in the master cylinder, kinked pipes, collapsed hoses, sticking brake cylinders, seized pads, cables or shoes and on and on to try your patience. 50% of the things we tackle are ok, the next 33% tackles your knowledge, 10% is a pain in the bum, 5% you wish you had never started and the last 2% drives you crazy. A bit like life really.

[Dormouse]

Diagnostic work is a bit like being a detective but with dirty hands. 40 odd years ago when I started in mobile tuning I just listened to the descriptions the driver gave me and asked simple questions in order to get a starting point. It didn't matter how mechanically adept the driver was, they just knew something wasn't right and all the clues were there for the finding. Women were generally the best at giving information, you just had to ask the questions in a way they were comfortable answering. Men were worse as they tended to hide any of their hamfisted attempts at repairs or tinkering. I was a great believer in tamperproof carburettors! Nowadays it is pretty eaksy peaksy when trying to get info from people as some men and women now seem to have equal levels of egos. Not trying to be disparaging, only noting the changes in society over time.

[RichardW]

Is this a manual handbrake or an electric one?

[Dispatcher]

Hello,

Sincere apologies for the delayed reply following all of these kind replies.

@Dormouse - The van has otherwise run ok; there is a cruise control issue now but that post-dates the issue I described in my first post. I will ask the garage to comment on your potential explanation - thank you! We are on the North Norfolk coast, a few miles from the sea. It's parked outside but in use multiple times a day rather than parked up for extended periods. The garage did inspect the brakes when I reported this problem to them.

@Pablo - In reltion to this question: "When this happens is the brake pedal hard and right at the top or is it normal ie progressive?", I wasn't applying the brake when this happened as I was trying to get away so I don't think I can answer this. If it happens again, I will try to remember to apply the brake so I can see.

@RichardW - this is a manual handbrake.

Thank you again,
Richard

[Dormouse]

cheers. let us know what you find. thanks very much.