Spongy Brake Pedal

[skyline2500cc]

Hi Forum

I have a Nissan NV300 van which was registered in March 2017. I am experiencing a spongy pedal when the engine is started, and the break pressed. The van some months ago needed rear disks so I replaced these along with pads all round. A recent MOT highlighted that the front discs now required replacing. Prior to replacing the discs, I noticed that the brake pedal was spongy. i changed the discs and tried the brakes and the pedal was still spongy. I know I don't have any leaks on the system so opted for changing the master cylinder. Unfortunately, due to no new master cylinders being available in Europe, I purchased a second hand one. I have bled the brakes all round and have a firm pedal without  vacuum however when I start the engine with my foot on the pedal the pedal slowly sinks to the floor. Could this be a vacuum diaphragm or maybe I have another faulty master cylinder. This van has already had a replacement master cylinder under warranty about a year  ago. I look forward to hearing from you experts.

[Local Apparent Friday]

Assuming that you replaced all the fluid and know how to properly bleed brakes, yes...what you're describing would generally indicate a faulty master cyl. and/or booster.

[radin2son]

Skyline2500cc

 Post a photo of your NV300. I’m sure many on this forum don’t know about these. Renault based, right? 

 

Awhile ago, I thought Nissan might import these... No for a variety of reasons. 

 

laf Moderator status! Good for you and the forum. 

Edited August 18, 2022 by radin2son

[skyline2500cc]

Hi I'm unsure why a photo would be helpful, but if ones required what would you like a photo of.

Had I realised this was actually a Renault Trafic with a Nissan badge I would never have have purchased it new due to issue I have had with Renault. Its done 30k miles and has had the following work carried out which is completely unacceptable. 

New master cylinder under warranty 1 year

New gearbox under warranty 3rd year

New gearbox bearing issue under warranty 3rd year

New battery no warranty 2nd year

New front and rear discs no warranty 3rd year

It now has a NOX  emissions issue which is a module costing in excess of £500

[radin2son]

A photo isn’t required. Just gives a view of a Nissan few in the US know about much less seen. An exterior photo and perhaps one of the cabin and engine compartment. 

 

How do you use your van? Work, passenger, camping...

[crusty]

NV300 is basicly unknown in this forum.  We are mostly based in North America and  most of the NVs people are here for are the NV1500, 2500, and 3500 body on frame construction not sold outside of North America.  The oddity is the Mexico built NV200, which is different than the European version. 

 

The issues you are discussing are unknown to us.  Because the vehicle is unknown to us.

[Local Apparent Friday]

@skyline2500cc Do you guys not have some kind of lemon law over there?  Sounds like a dud, for sure.  The info I gave is general mechanical advice and not Renault specific.

 

@radin2son Thanks, time to get to work.

 

For those not familiar, this is what an NV300 looks like.

[Local Apparent Friday]

4 minutes ago, crusty said:

The issues you are discussing are unknown to us.  Because the vehicle is unknown to us.

 

Yes and no.  While we don't have the Renault stateside, the issue described is a mechanical one not uniquely Renault, and generally is caused by air in the system/a fluid leak or a bad master cyl/booster.  But I'm sure the French say it much more eloquently.

[skyline2500cc]

Is it possible that the fault lies with the ABS. While I don't have any faults a leaking seal in the ABS would probably not be recognised by the electronics as a fault. I'm guessing that I may have a leaking seal.  Does anyone have experience of ABS faults and can you carry out any mechanical tests to diagnose the fault. 

[Local Apparent Friday]

Leaks are generally not mechanically tested, you just go over the whole system with a good flashlight, and it would also be accompanied by disappearing brake fluid, as in needing to top off your reservoir from time to time.  Somebody tried to patent a UV brake fluid to make this process easier, but it was abandoned.  Leaks are easier to find if you are not out in direct sunlight...perhaps in a garage or other space where you can control the amount of ambient light, or at dusk/dawn.  Good luck!

[skyline2500cc]

Sorry I wasn't understanding your post. I have tested the vacuum cylinder ( Booster) and if I press the brake pedal it travels 1/2 way. When I start the engine the pedal travels to the floor. If I run the engine then stop it , I can get 3 assists to the brake pedal. The final test I carried out was to press the brake pedal then switch of the engine and look for any movement in the pedal which there wasn’t. The test would indicate the vacuum cylinder is working correctly which makes me think it could be a failed seal in the ABS. This failure wouldn't be detected by the ABS electronics but I am told could cause the symptoms. I was just hoping someone else here had experienced the same problem before I rip out the ABS.    

Edited August 19, 2022 by skyline2500cc

[Local Apparent Friday]

Generally, that would be visually confirmed.  If you look at the connections and ports on the ABS unit, do you see any leaks or signs of past leaks (oily dirt residue where dust has attached itself to the fluid particles?)  Again, this is generic, non-renault specific advice...we don't get the 300's here so I'm not familiar with that particular ABS unit.