I did little bit search in the forum and can't find too much information regarding with brake fluid leak. During my last oil change, I noticed little light yellow oil around my front differential. I was suspecting it was my front differential seal leak, but now I am leaning more to believe it my brake fluid. The leak wasn't serious, it just a very slow leak. Yesterday, I flushed my brake with the pressure brake bleeder. After the flush completed, I noticed the a lot of brake fluid under my brake reservoir I believe the pressure brake bleeder must pushed significant amount of brake fluid though the crack, which caused the leak more noticeable. I did a test drive after the flush completed and the brake feels great, no issues. I made an appointment with my mechanic on Monday and now I am just debating whether to get the vehicle tow or drive down to the shop

There are no sponge feeling on my brake and I checked the brake fluid this morning, it was perfect. The leak has turned back to very slowly leaking. What are the chance for me to lose the brake power during the drive down to the shop because of the slow leak ?

 

How could it be leaking at your differential, what brake components are in that area? If your not loosing brake fluid it isn’t brake fluid, maybe antifreeze?

 

I don't think it the antifreeze. Maybe the brake fluid travel? Like if there is a leak in one the brake line, then the fluid just slowly travel to the diff area. I honestly don't know

 

What color is the trans fluid, monitor the brake fluid level closely for awhile

 

trans fluid is blue and my brake fluid level didn't even drop at all after 2 days being park

 

The brakes operate under very high pressure, driving will make them leak, not sitting parked. Drive it and monitor the fluid, Mark the level with a pen or pencil

 

Ok way too many things here let's take one at a time.
1) Sweating/oily front diff is fine. Mine has been this way for at least 5-6 years and probably more. Wipe off during the oil change and move on unless it really leaks leaving spots on the floor. That front diff has only 0.6L of fluid. If car has more than 80k miles I would flush it. Transfer case does the same.
2) Did you spill any brake fluid by chance? When doing brake job and pushing pistons back the level will go back up so if it was topped off it will overflow? Are you sure it's brake fluid? Brake res and master cylinder are unlikely to leak. The only thing that will cause a leak in braking system is either corroded brake line or old seal in the caliper both of which are likely to be in the wheel area.
3) how did you use power bleeder? Do you use dry (just build pressure with powerbleeder) or wet (fill up power bleeder with break fluid) method? How much pressure do you build it to?

 

1) I am not sure if my front diff is leaking The oil looks like is the brake fluid to me
2) Yes I did accidentally spilled the brake fluid during the flush I forgot to release the pressure before I unscrew the connector from the master cylinder. i cleaned up the best
3) I filled up the power bleeder with brake fluid and I built it up around 15psi to 25 psi. Most of time just 20 psi.

I already arranged an tow truck and bring the vehicle to my mechanic to check it out I don't think feel like putting people on road at risk. Hopefully it nothing major and the repair bill is reasonable. 2020 is such a rough year. Thank god we are more than half way done

 

uh this might be a problem. - you should only pressurize between 10-13psi. I am not sure of this, but could excess pressure have caused blow by of brake fluid?

 

Brake fluid pressure in the lines can go to 1000lb in full hard stops, it routinely is 4-500lb, that’s what powers the brakes so you stop!

 

right... post master cylinder. This pressure was applied before the master cylinder and could be cause a leak between the reservoir and the master cylinder.

 

Could have been also coming out through the cap I guess. I never fill up power bleeder, I just use it to build up pressure. 15psi is sufficient and make sure not to go below min level and do this on even ground.

 

Finally got my car back. It turn out no leak in the brake system. It was actually my front differential seal leak. The leak wasn't not serious and my mechanic recommend not to change the seal, just keep doing the the flush. It turned out really good after the repair was completed. The sad part was, the glk need a new set of fuel injectors, which is like $1700 oh well. Thx everyone for help.

 

why did you need new injectors?

 

The car had a rough idle and starts to smoke pretty bad during cold start. Injectors were leaking and my mechanic told me that if i don't replace the injectors, the engine may seize due to excessive fuel.

 

Oh you have diesel...gotcha. Wow that sucks.

 

With new injectors in place, I would keep a close eye on the valvecover area for any coal or bitumen appearing over the next several oil change intervals. Search "black death" and you'll know what I'm referring to. In short, it's caused by improper injector seal placement thereby enabling fuel and oil vapors past the injector seal during combustion. Quite common on Bluetecs for whatever reason, but especially if injectors have been worked on.

I would also recommend a cleaning interval for the fuel system, right before every fuel filter change (should be around 40K miles). LiquiMoly makes a product called Diesel Purge, it has helped many to restore their fuel injection issues including smoke, knocking, low power, low fuel mileage, etc.

 

I know about the black death, but it wasn't in my case. There were no carbon built up around my injectors. I think it just about time to replace at 160 000 km. I also used a lot of liquimoly products to address my issues, but didn't work. Oh well, the car runs perfectly fine now, which I am pretty happy

 

Interesting nonetheless. Were you getting any CELs or codes?

 

No codes at all. Just rough idles and white smoke comes out on initial cold start. Once the car warms up, i guess the injectors gets better seal, the white smoke will be gone and the rough idle will die down