crankcase sealing problem

[reeldutch]

i took the crankcase half of the motor again and to my surprize i could not find a good seal.
all the sealer was squeezed out.

i checked the case for warpage and its as flat as a pancake.
i checked it on a glas plate and it didnt wobble at all.
.006feeler gauge was able to slide in at some spots.
so that should all be good right?

i gues i just do something wrong sealing the case.

first i used permatex anearobic sealer 51813

second time i used permatex ultra black rtv sealand.

they both should do the job.

may be im just using it wrong.

method:

- cleaned surface left no gasket behind.
- whiped it clean with aceton
- let it dry for 3 minutes
- aplied a continues bead of sealer
put crankcase half back on and torquet it down.

let it drie for 24 hrs and restarted the motor.
motor run fine for 2hrs and same thing happens again.

i cant figure this one out.

 

[72SideWinderSS]

Re: crankcase sealing problem

" i checked the case for warpage and its as flat as a pancake."
If a .006" feeler gauge will "slide in at some spots", I wouldn't call that flat as a pancake.
Take some 400 wet or dry on that glass plate and lap the joint flat.

 

[reeldutch]

Re: crankcase sealing problem

double checked it with the feelergauge and .006 go's under and the .008 doesnt.

its in the corner where i tought the leak was comming from.

can somebody explain the lapping procedure i have never done it.

i dont want to mess it up

 

[72SideWinderSS]

Re: crankcase sealing problem

Tape a piece of 400 wet/dry to your glass, spray the paper with wd-40 or what ever you have like it, place your part with the face you want to lap down on the paper, move part in a figure eight, check your progress every once in awhile, stop when you have it flat.
Good luck,

 

[reeldutch]

Re: crankcase sealing problem

im gonna get to it today will let you know how it works out.
i read in the manual not to take more of than .010
that seems like a little to me.
so it should come of pretty fast?

reeldutch

 

[F_R]

Re: crankcase sealing problem

Pardon me while I get nervous here. Taking metal off the flange makes the holes for the main bearings get smaller and out of round. Then the case won't come together because the bearings are holding it apart.

 

[reeldutch]

Re: crankcase sealing problem

thats exactly the reason im asking people who have
seen this before.
i know some metal is comming off may be .005

the clymer manual tels me not more then .010

so if i believe that book(and i have not a lot of faith in that book) i should be ok right?

 

[ezeke]

Re: crankcase sealing problem

Wondering about the earlier procedure, did you apply a primer like "OMC Locquic Primer to the mating flange of the crankcase and let it air dry"? Quote is from the 1992 90 degree service manual #508147 page 4-22?​

Loctite Locquik 7649 is equivalent: "LOCTITE? 7649 is used where increased cure speed of Loctite anaerobic products is required. It is especially recommended for applications with passive metals or inert surfaces and with large bond gaps."​

http://64.242.109.170:8080/1/doc?id=26203​

Also, OMC Gel Seal II and equivalent products have a shelf life and that using it beyond one year without testing carries a risk of crankcase leaks.​

BTW, Loctite 504 has a larger gap capability than 518 - <.05 vs .015​

 

[reeldutch]

Re: crankcase sealing problem

ok,

i lapped the crankcover , i did 10 passages and checked.
after doing this 3 times i achieved feeler gauge .002 (the thinnest i have) can pass only at a few spots.
when i checked it i also put it on a black piece of paper an with a flaslight i looked for light gaps but there where none.

now the question is how much aluminum did i take of the threu crankcase cover surface , i dont think more than .001

the next step is to clean the block mating surface realy good and check for low and high spots.
im actually convinsed its fine because when i had it at the machine shop to bor some cylinders he checked for the heads and the cover.

- im going to clean the surface with acethone.
- i will use permatex anearobic sealer.
a bead of 1/4 '' thick
- torque it down to 30 lbs
- let it set for 2 days and than im gonna wake this puppy up again.

And if it barks at me again we will see who has the last word.

(i still have a 140 looper to rebuild)

reeldutch

 

[reeldutch]

Re: crankcase sealing problem

so i will seal it again tomorow i bought the surface primer from loctite item: 7471

loctite claims if you aply this on both surfaces you will be able to cure gaps up to .050 without prblems.

so i will let you guys know if there is a happy ending.

reeldutch