Crankcase ventilation

Demetris

Demetris

Well-Known Member
Hi all,

Judging from what i see in the engine breathing system it should really have negative presure in the crankcase as oil fumes are sucked in the carbs via the flame trap. However, when i take off the oil filler plug with the engine idling, there is air coming out along with oil droplets instead of air being sucked in. Is this normal?
I have changed the breather hose with another non collapsible item and i also think that i have cleaned the flame trap.
Could the blowby from the bores be so much that creates positive crankcase pressure?
But then it would burn lot's of oil, which is not the case. Any suggestions for what might be wrong?
 
You always will get oil droplets and fumes coming out with the filler cap off, the timing chain is thrashing around right next to it.
 
I have seen the cam gearwheel and chain in action and thought of this. I just make a comparison with my Austin which has basicaly the same crankcase ventilation system. When you take the oil filler cap off with the engine running then air rushes in and the engine almost dies from the mixture becoming too lean. Close the cap again and everything is back to normal.
I expected something similar to happen with the Rover, since it uses the same breathing system, and the same carb design with the oil fumes intake ports at the same place.

So, where's the catch?
 
harveyp6 said:
There's no camchain next to the filler cap on the Austin.
Click to expand...
True, there is nothing else that could create the difference, i have to accept it.

Thanks Harvey :)
 
You can test the crankcase presure by putting something like a latex glove over the filler hole and watching to see if it gets sucked in or pushed out (hold onto it, you don't want it to disappear into the engine).
 
Hi,
An old bloke I spoke to at last years Haynes Museum meet told me of a 2000 TC he had that burst it`s sump because the breather on the cam cover or flametrap had never been cleaned for donkeys years. I did mine as soon as I got home!!
Drew ???
 
Hello,

My name is Laurent Bruning, from the Netherlands, I just subscribed to this forum, and I have another question, maybe related to this one: the oil pressure of my 1975 2200 TC is quite high (over 75 psi when cold, while it used to be about 50) since I accidentily overfilled the engine a bit with oil. Since then the oil pressure has remained high, even after the oil level had returned to normal levels (which unfortunately happens rather quickly with my car).
I have cleaned the flame trap and carter ventilation as well but that didn't help. Someone else suggested that the release valve on the oil pump might be stuck. That's very hard to reach, I noticed.
Are there also any other possible causes for this high oil pressure?
 
4cyl engines do run a high oil pressure, but before you do anything you need to check what pressure you've actually got with a master gauge.It may just be a faulty gauge reading.

As for blocked flame traps and breathers bursting the sump, I can only assume the date of the haynes museum meet was April 1st. Have you ever tried punching a hole through a cast aluminium sump? Big ends making a bid for freedom do it OK, but crankcase pressure, before it ever got anywhere near high enough it would blow the breather pipes off, blow out the dipstick, or blow out the timing cover plugs along with every gasket, and vent the pressure that way. But burst the sump, I'd like to see that one. :D
 
harveyp6 said:
4cyl engines do run a high oil pressure, but before you do anything you need to check what pressure you've actually got with a master gauge.It may just be a faulty gauge reading.
Click to expand...

So how do I apply this master gauge, where do I attach it?
 
I made one from a gauge that I knew to be accurate fitted to a pipe with several interchangable fittins for the end. Then remove the gauge or warning light sender and screw in the master gauge, tighten up, start up and check the reading.
I'm sure they're available off the shelf somewhere if you don't want to make your own.
 
harveyp6 said:
I made one from a gauge that I knew to be accurate fitted to a pipe with several interchangable fittins for the end. Then remove the gauge or warning light sender and screw in the master gauge, tighten up, start up and check the reading.
I'm sure they're available off the shelf somewhere if you don't want to make your own.
Click to expand...
Ok, thank you for the information. By the way, I did that test of taking the filler cap off of the engine while running it yesterday, and I even didn't have to put my hand on it to feel whether there was under- or overpressure, because I could have used te wind coming out of it as a hair-dryer, so to speak... :O Oh well, the engine's done over 300,000 kilometers...
 
I've changed the P5B's oil gauge from electric to pressure because of the unreliability of the reading (& senders are expensive) of the electric gauge. You can do it in those as the gauges are standard but of course, the P6's were in-house & theres not really anywhere to mount extra clocks that looks any good though it's easier with the strip speedos.
 
On my strip speedo English car I've added extra gauges by hanging a P5B Coupe twin gauge pod under the dash top to the left of the clock/rev counter housing. Looks very professional.

Chris
 
I can never make my mind up whether I like the dials in the speaker grille though the P5 pods are the dogs danglys aren't they? I've just added one under the parcel shelf in the P5B. I'm planning on loading the 2000 S1 with gauges when I get round to it & have half formed plans involving drainage pipe of the right size though it will mean losing the dash shelf. Or I could collect a few more P5 pods. We'll see when I get the thing back on the road.. :;):
 
Thats no good, I had my electric window switches there,
p6stereo.jpg
 
Well, the problem's solved: I took the oil pressure release valve out and put it back again, and now the oil pressure remains at its normal 50 psi again, instead ofnearly 100 psi with a cold engine, as it was doing lately.
 
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