Sounds more like a power brake booster issue than the master cylinder. The booster should retain enough vacuum with the engine off, for power assited stops, for like 2-3 presses of the brake pedal. The noise you're hearing is probably a vacuum leak.

 

Interesting. Sounds more like a liquid squeezed through something than air. Ill dive under down to the pedals to see if i can locate a leak somewhere. Where is the vacuumhose connected on the powerbrake booster?

 

I'm not sure where the diesel is concerned, you may even have an electric or mechanical vacuum pump to drive it or it could use power steering fluid as a hydraulic booster. But the symptoms sound like a vacuum booster that has a leak.

 

Strange is that when i switch of the engine, the brakepedal is hard as it should be.
Its almost as when connecting the electronics some electronically opened circuit malfunctions. I am thinking like the ABS-system of maybe ESP/BAS. Is the hesitationproblem i am having with this Patriot maybe brakerelated?

 

This morning i clearly heard several times an air-escaping sound from down under at the pedals.

to be continued.

 

The sound got worse . Dived headdown to the pedals and managed to get a constant airleak whilst pushing the pedal down gently by hand.
I ordered another booster at Rockauto, should be here Friday.
Parked the green Pat, doesnt feel safe to drive. Luckely cars enough, good reason to use my '99 Durango, the wife uses my Pat.

 

Delay with brakebooster delivery(Fedex), still in their warehouse in south Norway. We got a bit of snow, look what i found on my driveway. Not appealing to work on it anyway

 

Brakebooster finally arrived Thursday, and i changed it yesterday. Took me 2 hrs , had to demount dieselfilter and 4 brake lines. Had to demount master brakecylinder and the bracket of 2 airco pipes. Not nessesary to demount the lines itself.
So had ofcourse to bleed the system.
Brakes basically work ok agian,no more escaping airsound. Mastercylinder was dry at the backside. But when i press the pedal real hard it sinks to the floor. No leaks anywhere, i choose a virgin piece of snow so leakage would be detected easily, but no.
So i expext internal leakage in the mastercylinder. Anyboby experience with this on their Pat?

 

Could still be air in the lines. So long as the abs hasn't cycled just more bleeding should fix it. I flushed my old fluid out myself initially using a gravity bleeding, then using an bottle with hose in some new fluid to solo pump bleed it. But i had to get the wife to pump the pedal while I bled the calipers to get a firm pedal.

 

I am used to that air gives a sponge feeling, the pedal really sinks to the floor ,also when pressing the pedal several times.
It feels the same as when bleeding the system. But this is the first time i work on a mastercylinder from a car with ABS.
I did the bleeding on my own with a rubberhose into a jar. Done that for 30 yrs on cars.

 

I must admit that i did not benchbleed the re-used mastercilinder since i did not have the equipment for it. I just filled it with the lines still disconnected till brakefluid came out at the line-connections and then mounted the lines.
Had ofcourse a container under it to catch the spil. The lines i closed directly after demounting with a closed rubber hose to avoid air into/ fluid out
In general i had to pump a lot(with engine running) to get any oil out at the calipers. It did not exactly run out easily.
I worked RB, LB, RF and last LF.
Am i missing something?

 

You could try bleeding it at the master by having an assistant pump up and hold the pedal, then crack the line loose to see if any air comes out.

 

Thx i'll try that

 

tried it but did not help. Will order a new mastercylinder. Luckely he is driveable , brakes work good, only when pressing pedal real hard it sinks slowly to the floor.
Luckely because my Black Betty now comes with an issue. Terrible noise from the right rear wheel , handbrake related.
Took first the wheel off to see if the plate on the backside touched the rotor but no. First had a slight scraping sound but later a severe scraping sound which disappeared again to come back later again. Rigging made it disapear 2 times temporarely , pulling the handbrake slightly while driving also , but later that resulted in a metal to metal sound.

I remember last week i had a severe TAK TAK TAK sound coming from that wheel driving 30 km/hr in town, which disappered as quickly as it came after i stopped to check. Thought i hit someting which got stuck in the rim. Lots of snow and ice here. But had the slight scraping sound since. Not alarming and having to fix wives green Pat first i did not check it out before.
I guess there is some part loose in the handbrakesystem. There is nothing to see on the outside.
Drove home 10 km up til 80 km/hr no sound. At home putting it in my driveway it made terrible sound again.

 

Ordered new master brakecylinder for wifes green Pat and tools to benchbleed the new master cylinder.

Also new handbrakeshoes for Black Betty. Bit of a guess, but quite sure that thats where the issue is and anyway good to have in stock.
Stuff should be here Friday , DHL this time.
Might open handbrake-assembly during this week to check.

 

The brakelights on the green Pat come on almost all the time, ofcourse not this morning when i checked it 10 times before sending my wife off with it to work.
While driving the lightbolt came on on the dash, i guess thats related. How to adjust the brake pushrod, i dont see how to do that.
I also read that the brakepedalswitch cannot be re-used ( i did not demount it) I ordered a new one but that sounds just very weird.

 

The brake light switch is an oddity. The first time I replaced mine I took the oem one apart to figure out why and found you probably could reassemble it back into it's factory setup to auto-adjust, but it's finnicky to do it. Thankfully they are a cheap enough part. I'm on my third one now and can confirm that it can cause a lightning bolt light too depending on how it fails internally.

 

Fixed Black Betty this afternoon. a spring to hold the brakeshoe in place was gone (broken/rusted?) only tiny piece left.
The pin of that spring and other springs and some other parts were loose and have been flying around creating noise.

Luckely i could use a spring of a 2CV of which i have many spareparts laying around. 2 other springs i could bend in shape again for the time being. I hope that with the handbrakeshoeset i ordered new springs follow.
Wife and kid can get to work/school safely. (she's a teacher)

Took wifes green Pat to park it in the driveway , no more lightningbolt on the dash and brakelights works normal.

Parts from Rockauto should arrive Thursday&/Friday.
Since we have 2 feet of snow i am not unhappy to have to use my 99 durango. Thirsty but plows through a meter of snow , the snowplough makes that at the entrance of my parking at my office. So at least there i dont have to dig away snow.
We have 10 -20 cm snow every dag for 2 weeks now. I want spring.....

 

Parts came today. Though advertised that hardware for mounting follows there was nothing else than brakeshoes in the box. I wonder where to find those springs. Maybe at the Mitsubishi dealer.

 

Found a set of springs for both sides at an AMCARpartsdealer here in Norway. 55 dollar but i guess beter expensive than not to get.
Curious how long it takes to get them, norwegian post sucks.
But i gotta fix wifes green Pat first anyway tomorrow. Found out how to adjust pushrod and bought a benchbleedkit for the mastercylinder as well.

 

Changed the masterbrakecylinder this evening and Todde your diagnose was probably right anyway. After benchbleeding the new mastercylinder and adjusting the pushrod i still had a pedal sinking to the floor. After bleeding the system thorougly the pedal became a lot better. The rear right brakecaliper was very difficult to bleed. I suspect a problem there and probably still a bit of air left there. Inside of the rotor was a bit rusty. I guess there is lack of pressure there.
Will look into the matter another day. Car is driveable again.

 

Changed the bleederscrew rear right, was a not original mounted, size 7mm, all others on the car are 8mm. Now i could bleed it properly and brakepedal is hard again. Car brakes normal again.
This morning the brakelights were hanging again, even stayed on after leaving the car. had to press the brakepedal once to get them off. I have a new switch laying around so i will mount it.

 

mounted the new brakelightswitch, that takes only 2 minutes, brakelights work normal again and cruisecontrol works again. I suspect and hope lightningbolt and ESP/BAS, car with snakes lights will not come bake.

 

I opened the old brakelight-switch. There is no electronics inside just mecanical parts.
Its easy to put it back together like the new one. Just prie off the cover and press the rod in a bit and twist the little lever counterclockwise 45 degrees.Then mount the cover again and ready to install again.
You cant do it with the cover on.
I see absolutely no reason why that should not work.
They may be cheap in the USA but my new one costet me 45 bucks, freight included.

 

Give the contacts a little emery or fine sandpaper love and you'll have a spare on hand!