Lotus Elan

Long Brake Pedal

PostPost by: AlanJH » Sun Jun 20, 2021 10:24 pm

I’ve been doing some serious lurking since joining the community in March with my first Lotus Elan, every time I have a question I find an answer already posted. But I’m really struggling with a long brake pedal, the previous owner, who did a lot of work in a short time, had replaced the front calipers, brake lines and rebuilt the master cylinder. I’ve installed the pads that the previous owner had, but never installed, which improved the feel, but several bleeding of the brakes later I still can’t get the pedal off the floor.
I’m totally out of ideas and have no confidence in the brakes because of never experiencing a pedal that doesn’t respond until almost to the floor. It is an SS so has the dual master cylinder but hopefully someone has some ideas on how I can get confidence in the pedal?
Alan Hill
1967 Elan S3 SS
Delaware
AlanJH
New-tral
 
Posts: 9
Joined: 13 Mar 2021
Location: Delaware, USA

PostPost by: richardcox_lotus » Mon Jun 21, 2021 6:33 am

I recently had this on a single master cylinder, after my local garage screwed up.

I found that placing a weight against the brake pedal overnight would help to bleed any tiny air particles trapped within the master cylinder.

It helped firm up the pedal a lot.

Regards
Richard
Richard
'72 Sprint
richardcox_lotus
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1249
Joined: 11 Jul 2004
Location: Kent

PostPost by: HCA » Mon Jun 21, 2021 9:04 am

AlanJH wrote:previous owner, who did a lot of work in a short time, had replaced the front calipers, brake lines and rebuilt the master cylinder. I’ve installed the pads that the previous owner had, but never installed, which improved the feel, but several bleeding of the brakes later I still can’t get the pedal off the floor.


My concern would be what was actually done by the previous owner - did he know what he was doing when he attempted the m/c rebuild...?

I am wondering if it not a good idea to start again?
Hal Adams

Evora - the poser
Elan +2 - keeps me busy
Macan - hers
Felicia Pickup - my favourite
HCA
Fourth Gear
Fourth Gear
 
Posts: 584
Joined: 03 Jan 2020
Location: Limoux, France

PostPost by: AlanJH » Mon Jun 21, 2021 11:16 am

Weighting the pedal seems like an easy thing to try, but, and this might be a rookie question, where does the air go? It has to go somewhere, is it followed by bleeding the system?
The previous owner had a mechanic that did all the work for him, but I was thinking along the same lines that maybe I should have the MC rebuilt again?
Alan Hill
1967 Elan S3 SS
Delaware
AlanJH
New-tral
 
Posts: 9
Joined: 13 Mar 2021
Location: Delaware, USA

PostPost by: Craven » Mon Jun 21, 2021 12:32 pm

Common problem with dual circuit brakes is air in the master cylinder, see
https://www.youtube.com/watch?v=vOuDEiwiozQ
Craven
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1277
Joined: 14 Sep 2013
Location: south coast uk

PostPost by: richardcox_lotus » Mon Jun 21, 2021 1:51 pm

AlanJH wrote:Weighting the pedal seems like an easy thing to try, but, and this might be a rookie question, where does the air go? It has to go somewhere, is it followed by bleeding the system?
The previous owner had a mechanic that did all the work for him, but I was thinking along the same lines that maybe I should have the MC rebuilt again?


As I understand it, the air that’s trapped in the MC, when under constant pedal pressure is essentially broken down into bubbles that are so so so tiny, they are able to pass through the gap in the seal and into the main reservoir, where they will rise and disperse.
Richard
'72 Sprint
richardcox_lotus
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1249
Joined: 11 Jul 2004
Location: Kent

PostPost by: baileyman » Mon Jun 21, 2021 2:00 pm

I tried this a number of times and I think it worked a little. What finally did it was Gary Anderson's advice to crack open the line at the master cylinder and then advance the piston until the bubble showed up. And it did!

John
Last edited by baileyman on Thu Jun 24, 2021 10:12 pm, edited 1 time in total.
baileyman
Third Gear
Third Gear
 
Posts: 304
Joined: 17 Aug 2017
Location: Boston

PostPost by: AlanJH » Thu Jun 24, 2021 7:37 pm

I tried wedging the pedal down but sadly no change. I’ve ordered a rebuild kit so I can take the MC apart and check it all out. Hoping the bore is good and no sleeve is needed. Wish me luck.
Alan Hill
1967 Elan S3 SS
Delaware
AlanJH
New-tral
 
Posts: 9
Joined: 13 Mar 2021
Location: Delaware, USA

PostPost by: nmauduit » Fri Jun 25, 2021 9:21 pm

I would investigate under 2 directions, in that order :

- make sure there is no air left in the circuit (can be more tedious than it seems, esp.with DOT5 fluid prone to small bubbles, and may involve bench bleeding the master cylinder and calipers)

- then if this consistently fails (and I understand the symptom is constant, not intermittent) check whether the pistons may pull back, leading to a need for more travel which can translate in a long pedal (esp. with a small bore MS and Girling 16 at the front, which is what I have) : then fitting springs (anti knockback) would solve that issue.

good luck !
S4SE 36/8198
User avatar
nmauduit
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 1763
Joined: 02 Sep 2013
Location: France

PostPost by: AlanJH » Sat Jun 26, 2021 2:47 am

I have to admit that I love the suggestions offered on this forum and I’m embarrassed to say I had to look up knockback springs. There is just so much knowledge and experience to tap into.
I’m running DOT 4 so I don’t have the DOT 5 issues, as was the previous owner. And I hope that one day I have the confidence to run the car hard enough to need knockback springs now that I know what they are.
Alan Hill
1967 Elan S3 SS
Delaware
AlanJH
New-tral
 
Posts: 9
Joined: 13 Mar 2021
Location: Delaware, USA

PostPost by: AlanJH » Mon Jun 28, 2021 5:14 pm

I now have brakes I have faith in for the first time since buying my Elan in March. I rebuilt the MC and the only obvious issue was the circlip holding the pushrod was floating around inside the rubber boot! I feel very fortunate the boot held the pushrod in place as that could have been a disaster.
Anyway, bench bleed, reinstall, bleed and everything seems good.
Alan Hill
1967 Elan S3 SS
Delaware
AlanJH
New-tral
 
Posts: 9
Joined: 13 Mar 2021
Location: Delaware, USA

Total Online:

Users browsing this forum: Chuck Nukem and 5 guests