TheSamba.com :: View topic - Idf sucking oil through breather hose type 4

Sun May 06, 2012 11:31 pm

My 1.7L type 4 bus motor with weber 40IDF seems to be sucking oil into one or both of the carbs. The easiest way to describe how the hosiery is set up is that the oil breather connects to the right carb and the evaporative emission control line is connected to the left. In between there are t-fittings that connect the two hoses together, sort of like if you grab both of your forearms with each hand. Sorry, I couldn't get a complete picture while the carbs were installed.

There is oily residue on the exterior of both portions of hose directly leading into the carb tops but the oil breather hose has this residue on its entire length. In addition there is oil accumulation on the top of the right carb air filter fixture, on the inside of the port and the inside of the hose to which it connects. Note: these pictures were taken after 3 months of dormancy and I live in a dry climate, that's oil on the hose not water condensation.

My assessment would be that the geometry of the hosiery plays a part in this because the oil breather is more directly linked with the right carb. So maybe reconfiguring to have equal lengths of hose from the breather and emissions T into one, loop around to collect fluids, then T into the carbs would alleviate this situation.

The carbs are currently out for rebuild and were not particularly dirty inside and one was not dirtier than the other. I will also reconfigure with a 34mm main Venturi as the previous owner was running with 28s. I dont know if the small Venturi size would create more of a vacuum on the end of the hose but that's a possibility too.

Does anyone have any ideas on this subject and please post pics of your aftermarket breather porting if you can and let me know how it works for you.

Thanks

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Mon May 07, 2012 4:34 am

Not uncommon cosidering the set up. You'd be better off running the line to a puke box/catch can then T'ing it to both carbs.

Mon May 07, 2012 6:48 am

You hose looks like it is both undersized and not suitable for use with oil.

Mon May 07, 2012 12:22 pm

Udidwht wrote:
Not uncommon for this setup

Can anyone vouch for this?

Wildthings wrote:
You hose too small

This is the size that fits onto the nipple of the breather box. If it were bigger it would not make a seal and might fall off...

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Mon May 07, 2012 12:31 pm

turtleneck wrote:
This is the size that fits onto the nipple of the breather box. If it were bigger it would not make a seal and might fall off...

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That doesn't stop the hose from being too small, check out the size of the original hose on a 2.0 FI engine, much larger in diameter and much shorter as well. You should go to a larger fitting in the top of the air cleaner. Good crankcase ventilation is very important to engine life, especially on an air cooled where the engine temperature can not be regulated in a narrow range. I have long believed that poor crankcase ventilation caused more damage to air cooled engines than heat.

Mon May 07, 2012 1:47 pm

Wildthings you may be correct, sir.

I've looked over this thread
http://www.thesamba.com/vw/forum/viewtopic.php?t=281850&highlight=oil+breather+hose

It appears that the later type 4 engines have a breather box with a cap on top and a larger port to suit a larger hose. The port on mine is 12mm and the hose attached is 3/4" (12.7mm). It appears as if the larger hoses may be in the ballpark of 1/2" or 19mm. Most, however seem to have the 3/4" hose.

If I attach a larger hose, in theory there will be less resistance, however the port will still have the 12mm diameter. If, for example you blow through a hose with a basketball needle on the end, it doesn't matter the diameter of the hose, the resistance is mainly a product of the diameter of the hole in the needle so a larger diameter hose would do little if anything to decrease resistance.

I understand your point on the importance of ventilation so maybe the ultimate way to go would be to get a breather box from a later engine... Btw what is the cap for??

Thanks for your input on the subject

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Mon May 07, 2012 2:05 pm

The cap is a vacuum regulator and you don't really need it. Early buses (dual carb) used the breather you have with no problems, as WT says that hose looks like it's not compatible with oil, maybe it's swollen shut internally? If a new hose doesn't help it's time to look at the internal health of your engine, too much blowby can cause that too.

BTW the hose from the charcoal canister should be on a separate fitting and in no way Teed to the crankcase breather.

Mon May 07, 2012 4:34 pm

busdaddy wrote: The cap is a vacuum regulator and you don't really need it. Early buses (dual carb) used the breather you have with no problems, as WT says that hose looks like it's not compatible with oil, maybe it's swollen shut internally? If a new hose doesn't help it's time to look at the internal health of your engine, too much blowby can cause that too.

BTW the hose from the charcoal canister should be on a separate fitting and in no way Teed to the crankcase breather.

you want to get a line rated for fuel and oil. Also put some copper wool or filter material between the crankcase and air cleaner so if you get a backfire the flame doesn't ignite the unburned fuel and air in the crankcase.

Tue May 08, 2012 8:15 pm

Busdaddy wrote:
These hoses should not be Td

Is it ok to do breather to one and charcoal can to the other or is it recommended to have two ports on each air cleaner?

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Wed May 09, 2012 10:39 am

This is what I'm going to try for the time being, run the breather to a small filter and the charcoal can to the carbs.

Comments?

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Wed May 09, 2012 10:46 am

turtleneck wrote: Busdaddy wrote:
These hoses should not be Td

Is it ok to do breather to one and charcoal can to the other or is it recommended to have two ports on each air cleaner?

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Either way will work, if your engine does produce excessive blowby you may want to Tee the breather to both carbs and add a separate port for the canister on one, that way both carbs can share the oily goodness :wink:

It's better if the breather goes back into the engine for combustion opposed to a filter, at least that's what Mother Nature says :P

Wed May 09, 2012 12:01 pm

Well I don't hate the earth so For now I'll port one to each and for the sake of balance and symmetry I will eventually split both lines into both carbs. Namaste.

Thanks to those who chimed in

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Wed May 09, 2012 12:46 pm

make sure you have a flame arrestor in between the case and carbs