Synthetic "710" change, blowby, & price questions - PeachParts Mercedes-Benz Forum

networkboy · #1 12-29-2007, 05:52 PM

Well, I finally got my Mobil1 5w40 into the car

Now my filler cap leaks even better (Gasket should be here on the 4th).
While I was grimey I did the tea kettle test and the fill cap burbles up about like a pot of water at a slow boil. About how much blowby does that indicate, and at what point should one worry about excessive blowby.

Also, how inter-related is blowby to compression? I have one cylinder that doesn't want to fire at idle unless the car is absolutely up to temperature. It's fine at anything above about 750 RPM, but below that it misses almost every stroke. Once the car is up to full running temp it only misses maybe 1/10 of the time. If all that blowby was from the one cylinder would that possibly be the source of my woes (Yes, yes, I know; compression check , injector checkout, etc.)

Finally, As to the cost of M1 5w40 diesel oil what is a decent per Qt. cost? I got mine at $6.68 for buying 12 quarts at once.

Cheers,
-nB

Skippy · #2 12-29-2007, 07:02 PM

The quantity of blow-by sounds about normal for a 24 year old example, but in your case it sounds like most of it might be coming from one cylinder. Blowby and compression are related, since both are indicators of the health of your rings. I think a compression check is in order.

As for how much blow by is enough to be worried about, since you already own the car, I wouldn't really be worried about normal (ie more or less the same from all cylinders) blow by as long as the engine still starts and isn't pushing oil out the dipstick tube. Even then, I had an old gasser that did that and I kept driving it for another year.

Hatterasguy · #3 12-30-2007, 01:00 AM

I'd check the compression, sounds like you have a dead cylinder.

Not to be negative but its probably not worth running real expensive oil in that engine. Cheap Walmart 15w40 is fine. Save the good stuff for when you sort it out, D1 isn't going to fix a dead cylinder.

networkboy · #4 12-30-2007, 01:46 AM

You're right it won't fix a dead cylinder, but the 5w part will make cranking a whole lot easier

networkboy · #5 12-30-2007, 02:15 AM

As to the dying cylinder (I won't call it dead till it never fires

)
Assuming it's not a fouled injector causing the issue and that there is substantial wear on the rings and cylinder, would a reasonable fix be boring out the cylinder and installing an oversized piston? or must one replace all 5 pistons as a set?

Compression test is in the queue before I rebuild the suspension.
-nB

charmalu · #6 12-30-2007, 12:22 PM

I wouldn`t assume anything. Looks like you don`t really know the milage
by the looks of your sig. and don`t know the maint. history of the car/
engine.

Have you done a valve adjustment? I would do that first before thinking
about a compression check. as far as the injectors you don`t know how
long or if they are original. the dead cylinder just might be the injector
not working and or plugged or?

Do the basics first, before you jump into the inerds of the engine.

as far as blow by, they pretty much all have blow by. It`s sort of a badge
or honor. more miles = more blow by

.

maybe we need a blow by badge to go along with the milage badge