April Site Wide Sale
We have detected you're not on the correct site for the car you have selected! Click the green button below to go to the correct site.
Select your car: 
BMW Mini Cooper
Select
 

 1275 engine

 Created by: ddt
   Forum Width:     Forum Type: 

 Posted: Feb 13, 2020 10:46AM
Total posts: 8374
Last post: Apr 9, 2020
Member since:Aug 14, 2002
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
CA
Dr Mini mentioned pressure is caused by what's going on in the crankcase. Much of the pressure in an engine sump, or in the case of a Mini the crankcase, is a result of blow-by getting past piston rings and valve seals. On each compression stroke, the air fuel mixture gets compressed. Piston rings are not airtight so a small amount of mixture gets by the rings. Individually it isn't very significant, but a 4000-5000 rpm and 4 cylinders, it adds up. THEN the spark plug fires and the mixture pressure goes way up as it burns, pushing the piston down. More of the semi-burnt mixture gets past the rings and into the sump. ALL internal combustion engines with pistons experience this. With insufficient ventilation, pressure will build up and result in leaking seals.

Early car engines (for example Chrysler in-line flat-head engines) had crankcase ventilation consisting of a draft tube. This came out of the engine and pointed straight down, with the end extending into the air stream under the car. At idle, you could usually see this little inverted chimney puffing gently. These cars typically had a thick coating of oil and road dirt on the bottom part of the engine and anything close.

Early Mini engines had one breather tube coming off the valve rocker cover and into the air cleaner body. They were small displacement, low compression engines running at modest rpms. As Dr. mini says, some engines, including the early 1275's had a second breather on the tappet cover. As Mini engines improved, 1275 engines and higher compression became more common. So did environmental issues. Positive crankcase ventilation is a system that positively vents the crankcase by reducing the internal pressure slightly so no fumes escape. The drawn out fumes get routed to the intake system and get re-consumed. The engine designers determined that the later 1275 engines (not sure about 998's etc.) needed lots of crankcase ventilation and that as much of the oil mist in it should be separated out before the fumes go to the combustion system. That's why my engine, and probably yours, has two canisters, one at each end of the engine. They would normally be connected by hoses to the carb or air cleaner housing so the fumes get burnt.


So, in short, don't compromise the crankcase ventilation. Running a hose or tube down under the car will be just messy, especially if you delete the oil separator canister. Some people have used those cute little pancake air cleaners, thinking it keeps dirt out of the crankcase, but have found they release oily fumes into the engine bay.

In the attached picture, you can see how my crankcase vents are connected to my HIF 44 carb. The black nipple on the base-plate of the air cleaner is where I previously had it connected. The white tube is the fuel bowl vent/overflow.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Feb 12, 2020 09:19PM
Total posts: 1656
Last post: Apr 9, 2020
Member since:Oct 18, 2011
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
You don't HAVE to have the breather on the cam drive case.... lots of Minis don't.  

What is true is that a good breathing capacity will probably help with oil leaks.  If oil leaks out the dipstick hole then more breathing capacity is definitely warranted.

The thing is that the interior of a Mini engine is one big hole so a breather (or three  attached anywhere will work.

If there's no room for the canister (oil separator) on the cam drive, then cut the can off and attach a hose to the remaining stub.  Depending on the state of tune/health of you engine you may need to lead this hose into a container ..or maybe just down under the engine so it doesn't dump oil onto everything.  Run the hose up as far as you can before turning it across and down.  You want the oil carried by the outgoing air flow to fall out and run back down the hose into the engine. Using as large a hose as you can will help as a bigger diameter hose will slow the air flow allowing oil to drop out sooner. 

Favourite places to attach breather hoses (all used on various models by the Factory) include the rocker cover, rear tappet covers, drop gear case .... and the cam drive case.  Any (or all  of these are suitable.  

Cheers, Ian

There's a whole other debate about what you do with the outer end of the breather hose(s).  Air filter case?  PCV valve to inlet manifold? Small aftermarket air filters?  Catch tank?  Straight to atmosphere?

 Posted: Feb 12, 2020 11:51AM
 Edited:  Feb 14, 2020 08:06AM
Total posts: 8252
Last post: Apr 3, 2020
Member since:Feb 7, 2006
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
Quote:
Originally Posted by ddt
Thanks for the help. I have a cover with a modified canister on order. It's just been a long wait. My other issue that started all this was a new aluminum radiator 1.5" wider than the stock so no room for spacer. I am trying to get it to run cooler below 190 if possible.
A super 2 core radiator is what a lot of Mini owners use here in Florida, it does the job and is Mini friendly as it is slim.


If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Feb 12, 2020 09:58AM
ddt
Total posts: 1
Last post: Feb 12, 2020
Member since:Nov 3, 2016
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
Thanks for the help. I have a cover with a modified canister on order. It's just been a long wait. My other issue that started all this was a new aluminum radiator 1.5" wider than the stock so no room for spacer. I am trying to get it to run cooler below 190 if possible.

 Posted: Feb 12, 2020 09:21AM
 Edited:  Feb 14, 2020 08:07AM
Total posts: 8252
Last post: Apr 3, 2020
Member since:Feb 7, 2006
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
Quote:
Originally Posted by ddt
what is the purpose of the blow by canister on the timing cover of the 1275 motor. I have fan clearence problems. Can the canister be bypassed
Don't by pass any breathers on a Mini they need all of them and some more sometimes.
As stated above you need to make sure the plastic fan if that is what you have fitted is flat as they tend to warp over time.
If it is flat you can buy the 1/4" spacer washers to clear the cannister you can use two if you have to, make sure the fan is installed the correct way with the smooth side to the engine.


If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Feb 12, 2020 08:18AM
 Edited:  Feb 12, 2020 08:20AM
Total posts: 8374
Last post: Apr 9, 2020
Member since:Aug 14, 2002
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
CA
When I got my Mini, it had a 1275 metro engine in it. The canister was intact and unmolested, but the plastic fan was on backwards and just cleared the canister. When I tried to put the fan on right, of course it interfered. Looking at my rad and ad cover, I noticed the fan had ample clearance to the rad and was not actually in the circular fan opening. I made a 1/4" aluminum spacer for the fan so it now clears the canister and into the circular opening in the shroud. With the fan in the opening, it is very effective at moving air - enough to blow leaves around in the garage.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Feb 12, 2020 08:14AM
Total posts: 8374
Last post: Apr 9, 2020
Member since:Aug 14, 2002
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
CA
Quote:
Originally Posted by dklawson
Good to see you posting Hugh!
+1 !!

.

"Hang on a minute lads....I've got a great idea."

 Posted: Feb 12, 2020 06:32AM
Total posts: 9165
Last post: Apr 8, 2020
Member since:Jun 5, 2000
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
US
Good to see you posting Hugh!

Doug L.
 Posted: Feb 12, 2020 03:35AM
Total posts: 6925
Last post: Mar 27, 2020
Member since:May 23, 2002
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
Because of everything going on in the gearbox, pressure builds up. On the small bore engines and the 1275 S motors they have vents on the tappet covers at the back of the engine. Without a vent/canister you will blow out the main seals in the engine. So, the answer is NO, you can't get rid of the canister. Someone used to sell modified ones that had part of the front cut off and a flat plate welded in place of the rounded part that was cut off. Most folk "gently massage" the front of the canister with a hammer until the fan clears.

"Retired:  No Job, No Money, Wife and I!  Will travel anywhere for Minis"

 Posted: Feb 12, 2020 03:17AM
ddt
Total posts: 1
Last post: Feb 12, 2020
Member since:Nov 3, 2016
Cars in Garage: 0
Photos: 0
WorkBench Posts: 0
what is the purpose of the blow by canister on the timing cover of the 1275 motor. I have fan clearence problems. Can the canister be bypassed