Injector pop tester - call it crazy but would it work? - PeachParts Mercedes-Benz Forum

ah-kay · #1 07-12-2011, 08:45 PM

If I can connect a hardline and a pressure gauge to the bleeding nipple port of a caliper, can I use it as a pop tester? It has a ready reservior of fluid and I just ask someone to pump the brake and I look at the pressure and the spray pattern. Would the master cylinder create enough pressure? Am I crazy?

When done, just bleed the brake and the car is good to go. It should be similar to doing a brake hydraulic pressure test.

1980sd · #2 07-12-2011, 08:49 PM

HE!! YEA IT'LL WORK!!!

wildest · #3 07-12-2011, 08:50 PM

Except that brake fluid has the wrong viscosity, you need diesel or a special oil to calibrate the injectors. Not a bad thought, though.

KenB · #4 07-12-2011, 08:52 PM

isn't there a different resistance for popping brake fluid versus popping diesel?

layback40 · #5 07-12-2011, 08:52 PM

You will need a very strong leg. No where near enough pressure.

ah-kay · #6 07-12-2011, 08:57 PM

A cylindrical cylinder of diesel can be put in line. If there is not enough pressure then all bet is off.

Came across this thread, brake pressure is in the order of 2000PSI. More then enough. If it is not a crazy idea then I will fabricate one, time permitting.

http://www.stu-offroad.com/suspension/bpress/brake-pressure.htm

79Mercy · #7 07-12-2011, 08:59 PM

HAHAHAHAHAHAHAHAHAHAHAHA no

Diesel911 · #8 07-12-2011, 10:13 PM

Let us know if it works!

Marvelicious · #9 07-12-2011, 11:02 PM

I think it'd be kind of a pain making pop testing a two man job, but what about using a master cylinder as another option for a home built pop tester.

tangofox007 · #10 07-12-2011, 11:07 PM

Quote:

Originally Posted by Marvelicious

...but what about using a master cylinder as another option for a home built pop tester.

Fluid incompatibility might be a showstopper.

ah-kay · #11 07-12-2011, 11:21 PM

Quote:

Originally Posted by Marvelicious

I think it'd be kind of a pain making pop testing a two man job, but what about using a master cylinder as another option for a home built pop tester.

It is not so much a PITA, 2 men job, husband and wife job. I will not be doing it every day. If I do, I would buy a professional quality pop tester. It is unlikely that it will be used for more than once a year. I may build one just on the odd chance that to replace the nozzles of the SDL.

Putting a small diesel container in line will solve the viscosity issue. This is the least of my worry.

funola · #12 07-13-2011, 12:13 AM

Better check compatibility of the seal in the MC to diesel first. The seals are made for brake fluid which is glycol based and may swell or melt with diesel and be ruined as a MC.

Stretch · #13 07-13-2011, 12:46 AM

Before you go any further make a rough measurement of the area of the piston in the MC and use the formula Force = Pressure X Area... you might then have a better idea if it will work or not.

mach0415 · #14 07-13-2011, 01:05 AM

Quote:

Originally Posted by layback40

You will need a very strong leg. No where near enough pressure.

Ditto. The question is rhetorical, since there are several factors, regarding Pascal's Law and how it relates to the pressures you are after. First, the average brake pedal has a 5:1 ratio of pressure out vs. in. So for $h!ts and giggles, 100lbs in = 500lbs out on the brake pedal to MC input piston. Add a brake booster and you have made it easier. Then, one must factor the surface area of the primary and secondary pistons of the MC to transfer into output PSI. Third, whatever the output piston is, overall psi is increased according to output piston surface area. A smaller piston acting upon a larger piston will increase pressure, but proportionately decrease piston travel. SO, if anyone is wondering if a MC could be used, then one might answer that question with a "maybe" depending on all these factors, piston sizes, fluid viscosities, etc. and pressure requirements of the pop tester. 3000psi is doable in a brake system. Diesel fuel WILL ruin a MC's seals. Could you build a hybrid system with glycol on the piston input side and devise an output side with a double seal with viton being on the diesel fuel side. As I think more on this, it seems like the hydraulic jack idea would involve less engineering.

ah-kay · #15 07-13-2011, 03:08 AM

The diesel container I have in mind is in line between the brake bleeding port and the hardline to the injector, outside the car. I am not that daft to fill up the brake reservoir with diesel.

The brake fluid probably is OK if I only interested to measure the pop pressure and the pattern is not out of whack. The brake pressure gauge is calibrated up to 5000psi so there is a good chance the pressure will be 135+bar. It is a go for me unless there is a show stopper issue.