Oil level problem

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jphoenix
Posts: 105
Joined: July 12th, 2013, 7:41 pm

Oil level problem

Post by jphoenix »

I've put 8.5 hours on my engine, done two races and numerous practice sessions and I'm struggling with finding the correct oil quantity for this engine. It has a very large external oil cooler and filter. When I fill it so that its up to the second mark on the dipstick (hot, after a race with engine idling) the engine blows it out all over the back of the firewall where it runs down and fills the cockpit with oil. It also burns it out the number three cylinder, for some reason that's where it wants to burn excess.

I checked everything to make sure nothing was wrong with the number three jug, compression is good (123, as are all the other cylinders), and the blue smoke goes away once the engine has tossed all of the quart of oil I added after the last session. This past weekend, I gave up and just left the oil level at halfway between the first mark and second mark on the dipstick and it ran fine, no oil out the front seal (worm gear?) and no blue smoke. I did not measure (in inches) the height of the resulting oil level, but I can.

Any ideas why I should not be able to run an oil level per the book, so to speak? Something I'm missing. I drained the oil when I got home and it had just over four quarts, maybe 4.5 qts at the most when I add the residual left in the filter. Again, this has a large, say 6" x 10" external oil filter, associated lines and filter, I would expect half a quart in the external oil system itself.

Engine has good oil pressure at idle when hot, no loss of pressure in corners, never see the light on either, so what do you guys think?

Jim
Jim Phoenix
2016 Red Mercury FV 44
JSM 16
Posts: 21
Joined: April 6th, 2012, 7:18 pm

Re: Oil level problem

Post by JSM 16 »

How is your system vented, if your oil system not vented properly this will create to much case pressure causing oil to blow everywhere
jphoenix
Posts: 105
Joined: July 12th, 2013, 7:41 pm

Re: Oil level problem

Post by jphoenix »

Vented to a catch tanks with a big ID hose. I spoke with Dietmar and he gave me some ides, mostly making sure the car is level when checking the oil, I think that's where I'm going wrong. I raise it up on my stand after the race to check the oil, etc. and it's not level, tilts about 5 to 10 degrees right, so that may be part of the problem.

Thanks,

Jim
Jim Phoenix
2016 Red Mercury FV 44
FV80
Site Admin
Posts: 1169
Joined: June 27th, 2006, 9:07 am

Re: Oil level problem

Post by FV80 »

Another thing to consider is checking the oil HOT and RUNNING. I have never been able to determine proper oil level when the engine is cold - I have to just guess. I have no idea why, but it 'sticks' about a quart LOWER when cold than it does hot. (this is several different engines in at least 2 different cars) With any sort of external cooling/filtering, it is also nearly impossible to determine just how much is in the external parts at 'check time'. In my situation, the oil temp has to be well above 100 degrees - more like 150 before I can rely on the dipstick reading .. and only then with the engine running (at idle) .. and the car decently level, of course.

Steve, FV80
The Racer's Wedge and now a Vortech, FV80
To sign up in the FV Registry for updates about SCCA Formula Vee, please send me an email or PM with your name, location (city/state), make/model of car, phone # and any other appropriate info.
cendiv37
Posts: 386
Joined: June 25th, 2006, 7:29 pm

Re: Oil level problem

Post by cendiv37 »

Steve,
At those conditions: engine hot, running at idle above 150F, car level, what oil level do you target?

I have been told to target the stock oil level mark under those conditions.
The higher marks are the best one can do for a non-running level, but as with you, I have great difficulty getting any consistency with non-running level measurement.

FV's simply ARE a pain in the backside to get and maintain the correct oil level on. Anyone who says otherwise either has a good "system" that works for them or is happy overfilling it and letting the excess blow into the catch tank. I hate driving behind the latter...

My "system" is to put a known amount of oil in the car after a full change, including filter. I also try to let the oil drain for a long time during the change (days) since I usually do changes with cold oil in the shop at home. I hate changing oil at the track because it invariably leads to oil all over the top of the case, down the sides and into the belly pan (oil filter removal). With no external plumbing and a Type 4 cooler my standard fill is approximately 4-1/4 quarts. 4 quarts even would probably be enough to get through the first session to where I can check it hot and running at idle, but I'd rather have a touch more. Note: my extended sump is fairly small, smaller than I'd like. I then try to check it hot and running after the first session, topping up to just a hair over the stock VW mark at the conditions you describe above.

My theory as to why the oil level is so hard to judge, especially cold, is that the correct non-running level of oil is right at a level that has a varying open cross-sectional area in the engine. The bottom of the crankcase is roughly square and meant to hold ALL of the oil in a stock VW. We need more. As you go higher, the case necks down from the full cross-section of the square oil crankcase to the area of structure supporting the cam. This leaves a much lower open cross sectional area inside the case. Thus as you fill the engine from empty, the level reading changes slowly as you fill the main crankcase, then it changes fast as you fill the necked down area just below and around the cam. Just a bit higher and you start to fill the pushrod tubes and valve covers. At that point, you can add a lot of excess and see little change in level because you are filling pushrod tubes and valve covers. There is no "linearity" to the reading you get just about at the point that you most need it!

Oil draining down from the crankcase is also a problem. That's why you get a low reading if you try to check it on a cold, running engine. Much of the oil is still up in the crankcase draining slowly back to the sump due to it's high viscosity. I don't like to run my engine off the track long enough to get the oil truly hot because by then I've cooked the heads... That's also why I drain it cold at home.

I have also found that I get reasonable results shooting for the high mark as long as I check it fairly quickly after running a session. This would be car level, engine hot, maybe 5 - 10 minutes after running. This allows time for all the oil in the engine to drain back into the sump, but does not allow time for additional oil to slowly drain out of all of the oil passages, lines, cooler and filter. If I wait too long, the level will be high, above the high target mark. This is also what I see if I check the oil after the car has sat in the shop for a few days: higher than the high level mark.

That's my $.02
YMMV as they say.
Bruce
cendiv37
FV80
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Re: Oil level problem

Post by FV80 »

Agreed, Bruce,
At HOT/RUNNING, I use a 'higher level' mark that is approx 3/4 qt above the normal full mark. I have external oil cooler and filter via a block at the oil cooler spot on the top of the case. If, for some reason, I don't get to check the oil before the engine cools after a session (that is always my FIRST goal after every session), I generally add about 1/4 qt per session just on general principles. If I'm lucky, I occasionally get a 'little' oil into the catch tank (which is CLEAR - an old clear oil bottle) after the next session. I keep the bottle emptied and am happy when I put 'just a dab' of oil into the bottle each session. The case and engine area stay "clean" (more or less :) ) and I'm confident that I could not put ANY more oil in the engine without making a mess.

With a new engine install, I put in 4 1/2 qts and then check it and top off after the first on track session. If I'm overly concerned for some reason, I run the car up/down my driveway to get it hot enough to check before loading. Fortunately, I have a reasonably long driveway (1/4 mile) and JUST BARELY enough room to turn the car around for another run at each end.

I did have a situation several years ago now, where the engine would blow out too much oil. Rollin and I went SEVERAL ROUNDS with it - spinning bearings each time and trying new things to keep the oil in the engine. This was 1 of 2 basically identical engines - the other one was fine. Finally, I told him to just CHANGE THE CASE - we had nowhere else to go. For whatever reason, the new case FIXED the problem (all other parts were moved to the new case). We were never able to come up with an explanation for the problem.

Steve, FV80
The Racer's Wedge and now a Vortech, FV80
To sign up in the FV Registry for updates about SCCA Formula Vee, please send me an email or PM with your name, location (city/state), make/model of car, phone # and any other appropriate info.
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