anyone has trouble with harbor freight compression tester? - PeachParts Mercedes-Benz Forum

Nate Stanley · #1 08-09-2007, 02:35 PM

Hi all!

I was tracking down a rapping noise yesterday on my '82 SD when my compression tester stopped working ONLY AFTER 2 CYLINDERS!

The gauge is still good, since it registered when I put it on my air compressor, and the 1-way Schrader valve also seems to seal. It is in the fitting that screws into the injector adapter. there is no obstruction in the flex hose. I'm suspecting the quick disconnect, but I can't be sure.

The gauge needle moves, it just won't build pressure.

Have any of you experienced this?

I know U get what U pay for, but I really expected better-

TX76513 · #2 08-09-2007, 02:42 PM

I have not had any issues with mine. Take it back, they will give you another. I'm not that brand sensative anymore - even Snap-on has issues with quality anymore.

toomany MBZ · #3 08-09-2007, 03:26 PM

Mine worked only once. My tester is a U.S. General, on the end there is an "o" ring that came off, perhaps when I removed the tester before releasing pressure, and I didn't realize, got another one. I bought it from here http://**************.com Just took a look at it, can't see the where the "o" ring resides, but it's been working ever since.

Nate Stanley · #4 08-09-2007, 05:09 PM

John, thanks for the reply. I lubed my release valve with light machine oil, and it seems to hold pressure-

Toomany,
the O-ring idea has merit. It was getting late in the day and it may have slipped off- since you got another one, could you please tell me where it goes?

Thanks,
Nate

Nate Stanley · #5 08-10-2007, 05:51 PM

it resides deep down in the quick-disconnect fitting, beyond the tiny ball bearings that secure the mating fitting. It must've flown off just like toomany's did, because I remember releasing the QD before bleeding the pressure on the last cylinder I used it on.

remember kids, bleed pressure first, disconnect quick release second.

Nate Stanley · #6 06-29-2009, 12:22 AM

OK guys, troubleshooting time. THis all started when I got a knocking / rapping sound on the way home from work one day almost 2 years ago.

I was doing a compression test when I lost the O ring on the tester's quick release, NOW- I got another tester, values were:
#1 395
#2 385
#3 200
#4 365
#5 360

The noise does not get deeper with increased engine speed.

Oil pressure is fine, though I believe a malfunctioning gauge sender gave me a false positive and I may have run the engine low on oil for a short time. Once I heard the noise, I limped to an auto parts store and topped off the crankcase. It was at least 3 qts low. This engine does have a lot of blowby.
SOOOO,
I drained the oil today and pulled the pan. I found:

1) the O ring from the compression tester
2) some tiny bits of what appear to be plastic or gasket cement
3) No, repeat, NO bearing fragments or metal debris of any kind. \

I cut apart the oil filter, found the usual sticks and cotton waste in the upper section, and some tiny metallic fragments, no more than .010" -.020" in size in the lower section. Total qty may have been 50-70 evenly distributed thru the pleated filter.

I have yet to yank the head, but will do so soon. In trying to rule out the lower end bearings, I have 2 questions:

1) Is that sort of debris in the oil filter normal for a high mileage engine?

and

2)has anyone ever lost a rod bearing or main bearing and NOT had any metal debris in the oil pan?

Any insight based on experience here will be most welcome.

Thanks and best regards,

vstech · #7 08-09-2007, 03:20 PM

the release button on mine has to be fiddled with on each test... kinda strange that it sticks in the open position...

Diesel911 · #8 06-29-2009, 10:51 AM

I don't believe the O-ring on the Compression Tester got inside of the Engine as the tip of the Precombustion Chamber has small holes. It must have been somewhere on the exterior and fallen into the drain pan.

The only place I can think of that an O-ring could get into the Oil Pan is from the Stem on the Oil Filter Cap. Where it seals goes back to the Oil Plan.
The other place would be if you had the Oil Fill Cap on the Valve Cover open and the O-ring managed to go through the Hole.