tegwin
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| posted on 14/5/09 at 09:01 AM |
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Crankcase breathing and engine leaks?
I have been having some issues with my TR6 engine leaking oil.
One of the suggestions from the TR forum guys was that their might be some blow-by on the pistons causing high crankcase pressure....
Fitting a breather to the crankcase would prevent the oil from being pushed out of the case...
They suggest fitting one of a classic volvo 112S to the hole where the mechanical fuel pump used to be in the middle of the block..
I can see the logic behind this... but how does the crank breather work?
Is it literally an open vent to atmosphere... or should there be some sort of valve/filter to prevent the oil escaping and only allow the air out?
I could just drill a hole in the blanking plate... screw in a nipple and run a hose to the top of the engine bay with a filter on it... would that
work? or would I end up with oil pissed everywhere?
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tendoshingan
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| posted on 14/5/09 at 09:21 AM |
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Not sure on TR6 but on the zetec I have two breathers connected to an aluminium bottle, the engine pressure is never too much and seems to breathe
fine.
Ususally have a filter on top of the bottle, but have run it without and there never seems to be oil getting out.
For my breather in the block I did eactly as you suggested and drilled a hole in a blanking plate then welded a pipe that the breather tube could be
fastened too. Works fine.
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tegwin
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| posted on 14/5/09 at 09:25 AM |
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One of the TR guys was actually suggesting using an oil catch bottle...
He has his plumbed to the old "volvo crank breather" and also to his rocker cover... but I cant figure out where the oil goes once it gets
into the catch tank... is there a return to the crank?
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cd.thomson
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| posted on 14/5/09 at 09:29 AM |
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quote:
Originally posted by tegwin
One of the TR guys was actually suggesting using an oil catch bottle...
He has his plumbed to the old "volvo crank breather" and also to his rocker cover... but I cant figure out where the oil goes once it gets
into the catch tank... is there a return to the crank?
no it stays in the catch tank, I think the idea is it doesnt just fill up, it just catches tiny bits of oil that come through. If its quickly filling
up with oil then theres something wrong
[Edited on 14/5/09 by cd.thomson]
Craig
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tendoshingan
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| posted on 14/5/09 at 09:30 AM |
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Yep that's roughly what I (and plenty of others with zetecs) have done, pipe going from bloack and pipe going from rocker cover to an oil catch
tank of some kind, that usually has a filter on it.
The oil doesn't really go through the breather, what you get is some oil but mostly hot gasses that evaporate when they get to the oil catch
bottle so no reason to have an oil return.
There will be a loss of some oil over time but this is easily replaced as per normal oil checking.
(ooh just got to 100 posts  )
[Edited on 14/5/09 by tendoshingan]
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tegwin
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| posted on 14/5/09 at 09:37 AM |
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100?.... You have a long way to go before you can access the shop I fear!
Hmm... The rocker cover vent feeds back into the intake manifold... I guess I should leave that one as it is and just add an extra breather do the
crankcase?
I dont really want to add a tank to the engine bay unless I have to..
Is there any reason why I cant just have a hose with a filter on the end? (or would a tank be the more sensible approach?)
The blanking plate for the fuel pump is 2mm thick and I cant get it to stop leaking... So I wonder if there is a buildup of gas behind it causing
the leak? (I guess 2mm should be plenty thick enough for a blanking plate)
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Another silly question... if the oil pressure guage registers 50PSI... where in the engine is that pressure? I dont want to put an atmopsephric
vent onto something that should run at 50PSI....
On the TR engine the fuel pump runs directly from the camshaft....(push rod engine)... so the void where the camshaft runs wont be at 50PSI will
it?)
[Edited on 14/5/09 by tegwin]
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AndyGT
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| posted on 14/5/09 at 09:41 AM |
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on standard cars the breather normally goes through the inlet manifold and the nasty hot gases are sucked through the engine and burn't. Not a
good idea on older higher mileage engines as this causes coking on the back of the valves etc.
On my oler road cars I usually put the breather in a bottle or in the chassis leg. The oily hot gases will then lube your chassis legs and help
reduce corrosion!!!!
nothing is impossible
everything is possible
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frodo_monkey
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| posted on 14/5/09 at 11:34 AM |
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quote:
Is there any reason why I cant just have a hose with a filter on the end? (or would a tank be the more sensible approach?)
Hows about...
If it does blow out some oil a tank will hold it. Otherwise hot oil could end up on your exhaust (cue massive fire) or on your brakes/tyres (cue
slippery fast crashing death) 
Get yourself a catch tank, most decent ones have a sight gauge to check that it isn't filling up - and maybe a filter (not that you really need
one). Any decent tank will have a removable bung at the bottom so that you can drain the watery dregs periodically. Failing that use the pikey
solution of a plastic drinks bottle with a hose taped into the top 
With regard to the oil pressure question, have a look on the side of the crankcase - you'll normally find some kind of boss with a screw-in
pressure sensor near the bottom of the sump.
[Edited on 14/5/09 by frodo_monkey]
[Edited on 14/5/09 by frodo_monkey]
"Racing is life. Anything before or after is just waiting."
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DarrenW
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| posted on 14/5/09 at 11:45 AM |
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On a pinto they haver a PCV - positive crankcase valve. Basically the pCV is connected to the inlet manifold such that the vacuum created by the
running engine opens the valve and allows the gasses to be sucked in and burnt off.
On modified pinto's (ie with multiple carb set ups) the pipe to inlet manifold is taken off. The PCV can either have its valve taken out and
gasses redirected to catch tank, or either a aftermanket fitting added / cortina sytle breather. The cortina breather is similarly usually connected
to inlet manifold but doesnt have the valve inside, instead it is a larger can that has a baffle plate to stop heavier oil particles being ejected and
the gasses vent to atmosphere (or catch tank if fitted).
It sounds like the TR guys are proposing a similar type of set up as used on modded pinto's.
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DarrenW
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| posted on 14/5/09 at 11:51 AM |
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I wouldnt suggest a straight hose from breather hole with filter on end. I experimented with this - you may recall seeing several catch tanks with
such filter. In my experience the filter gets clogged quickly with gaseaous spoils and the air movement splatters the spoils all over. Venting into a
can allows the gasses to condense first. In the end i cut the top off my catch tank and havent had issues since. I dont get a lot of spoils into the
tank though, some people get fairly rapid filling on track days meaning emptying is required, an open tank would obviosly be an issue if this
happened.
Have you exhausted the simple stuff first before assuming the pistons are allowing crankcase to get pressurised? I had an issue early on with
overfilling (caused by incorrect dipstick). This caused all sorts of bother. Once oil level was corrected its been fine ever since. On Pinto's
it has been known that if you fill sump to top mark on dipstick they can be troublesome. Many people report breathing is much better when filled
between lower and middle mark.
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Andi
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| posted on 14/5/09 at 12:52 PM |
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I used a posh pikey aluminium cycling can.
My pintosaurus runs between 70 and 80 psi. I have always wondered if that was too high.
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