Low oil pressure, but with high oil pressure?!?

Ian Epperson

Hey guys, I've been driving around with Jake Raby's Type4 Torquer with DTM shroud for many years now - and it usually runs like a top. I know what to expect from the engine, and have used the heck out of it for over 6 years. It has an external oil filter, oil cooler w/fan by the transaxle, as well as the stock T4 oil cooler set up in the DTM shroud. I was driving this last Saturday up an incline on the freeway, when it lost power and seemed to dump oil.

Short version: After warming up, the engine suddenly has dangerously low oil pressure, yet is leaking oil from everywhere. After shutting off the engine, the dipstick shows no oil (!!) and white smoke comes from the oil filler (!!!!) but after it sits for a few minutes, the oil magically returns. Also, is firing on only 3 cyls (??).

Longer version: I've long had issues with my home-made breather box. I always have a bit of oil flowing into the carbs, and a couple of times (usually after I've been doing around town driving, then hit the freeway for an hour) it's stranded my by blowing oil into the carbs. The first two times, I dismantled the carbs by the roadside to clear the oil, but the last two times I just checked everything, let it cool a bit then ran it for a minute until it cleared and ignored the tailpipe oil smoke.

I normally run with Brad Penn (partial synthetic) 20w50 or 10w30 summer/winter. On my last oil change, discovered the shop that sells it went out of business, so I instead used Royal Purple (fully synthetic). Following that oil change, I drove from San Francisco to Reno and back and the mileage went up from expected 18 MPG to 22 MPG.

Saturday, I was driving up over the Oakland hills through the Caldecott tunnel, and it started running rough going into the tunnel. Head temp was a bit higher than expected, but oil temp and pressure was spot on what I expected (about 50 PSI). In the tunnel it got worse, maybe running on 2 cyls? There's nowhere to stop though. Just before getting through, the oil temp started dropping, and just as I got out of the tunnel and shut off the ignition, it dipped below 5 PSI and my light came on. I pulled off and left a trail of oil. Had it towed home.

At home, the oil levels were fine, and all the oil on the ground had sprayed from the breather box vent. I cursed a lot, then reworked the breather system. Two taller boxes, cross connected and with an added vent for the oil filler. The cross connect has two additional fittings at the highest point that connect to the top of the air filters on the carbs.

I just got it together last night. But when I took it for a short drive, it was still missing on one cyl - I thought it was maybe still oil in the carb, but it didn't seem to clear. Just before getting back to my garage, the oil pressure started dropping again, and as I pulled in and shut it off, it was down around 5 PSI. There was oil leaking from the push rod tubes and had been squirting out the dipstick tube. The dipstick showed no oil, and white smoke came from the hole, as well as from out of the air filters on the carbs (through the new breather system) and from the oil fill. I added a quart, and saw that the oil was back up to perfect, cursed quietly, then went to bed.

Any ideas? I'm pretty sure I no longer have a breather problem, but smoke is not good. The paradox of low oil pressure and oil leaking everywhere as if the case pressure is too high has me scratching my head. Did the new all-synthetic oil break down deposits and clog up the new oil filter? Can this somehow be an oil pump issue? Did the engine overheat and I not know it, and maybe affected the valves causing a cyl to not fire? I'm stumped.
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mcmscott · Posted: Wed Jul 02, 2014 2:53 pm Post subject:

Oil pressure and crankcase pressure are 2 different things and in no way are related. Burning oil will lead to detonation(bad breather system) causing a piston to burn, causing extremely high case pressure. Hope that's not it, but that is my first thought
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busdaddy · Posted: Wed Jul 02, 2014 3:12 pm Post subject:

A compression test will help answer alot of questions.
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Anvil · Posted: Wed Jul 02, 2014 3:16 pm Post subject:

Is it possible you're pumping oil into the cylinders and hydraulically locking it up?
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Ian Epperson · Posted: Wed Jul 02, 2014 5:02 pm Post subject:

Thanks for the replies. I'm heading out camping tonight (sigh, without the VW) and I'll do a compression test early next week.

mcmscott: your reply makes a lot of sense... damn.
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busdaddy · Posted: Wed Jul 02, 2014 5:07 pm Post subject:

mcmscott · Posted: Wed Jul 02, 2014 5:27 pm Post subject:

74 Thing · Samba Member Joined: September 02, 2004 Posts: 7630

I would not run breather hoses into the carbs. That would be a starting point.

sloboatnova · Posted: Thu Jul 03, 2014 5:41 am Post subject:

One theory would be that the extra oil in the cylinders has glazed the walls of the jugs causing extreme blowby which could cuase extra crankcase pressure and oil leaks and loss of pressure.
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modok · Posted: Thu Jul 03, 2014 4:51 pm Post subject:

Too many miles on dusty dirt roads and now the rings are dead.

You need better airfilters. Better elements to fit on a weber could be made........but aren't. Sorry man.

mcmscott · Posted: Thu Jul 03, 2014 5:28 pm Post subject:

74 Thing · Samba Member Joined: September 02, 2004 Posts: 7630

Sounds like pistons and cylinders-may have to tear it down.

modok · Posted: Thu Jul 03, 2014 5:39 pm Post subject:

Yes that giant canister filter would do. Would be nice to have something more middle of the road tho, you know, between crap and overkill Wink

mcmscott · Posted: Fri Jul 04, 2014 7:19 am Post subject:

http://www.cbperformance.com/ProductDetails.asp?ProductCode=3388

A pair of these plumbded into a decent filter would work well also, probably not as "overkill"
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Towel Rail · Posted: Fri Jul 04, 2014 12:31 pm Post subject:

Hey Ian, I haven't been keeping up with your engine odyssey, but did your Type IV always need the breather box? Have you tried going without, to see if the engine can keep the oil where it should be?

With an oil filter and (some kind of) air filter, I'd think that the engine should have gone a while before needing any of that.
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esde · Posted: Fri Jul 04, 2014 12:49 pm Post subject:

If the motor is tending to blow oil out of the breather, having the breather box plumbed into the air filter(s) is just going to make it worse. I've never had the need to connect them to the air filter, but have removed that connection on a few engines where crankcase pressure was blowing oil into the carb. Mysteriously, when the filter connection was eliminated, the volume of oil in the breather box was lessened.

esde · Posted: Fri Jul 04, 2014 12:49 pm Post subject:

If the motor is tending to blow oil out of the breather, having the breather box plumbed into the air filter(s) is just going to make it worse. I've never had the need to connect them to the air filter, but have removed that connection on a few engines where crankcase pressure was blowing oil into the carb. Mysteriously, when the filter connection was eliminated, the volume of oil in the breather box was lessened.

Ian Epperson · Posted: Mon Jul 07, 2014 11:02 am Post subject:

Ian Epperson · Posted: Mon Jul 07, 2014 11:11 am Post subject:

Ian Epperson · Posted: Mon Feb 23, 2015 10:10 pm Post subject:

Arise, my frankenthread!

Man, it's been a real busy few months - bought the house we've been renting, worked some side jobs to raise cash, and the Thing has sat and sat, staring at me in the garage. I ordered a cheap inspection camera from Amazon.com, and this last weekend rented a compression tester - which didn't have the correct adapter %$&^! Another Amazon.com order, and I'll see the adapter tomorrow.

Anyway, pulled the plugs and discovered 1, 2 and 3 wet with oil, but 4 is dry. Inspection camera showed cylinder tops that look like overused frying pans Embarassed

. As I rotated the engine to move the pistons down, I watched oil seep around the rings of #1 and #2.

Piston #2:

Image may have been reduced in size. Click image to view fullscreen.

None of the tops were smooth as far as I could tell, but #4 seemed particularly bad:

Man is it tough to get good images with that camera, but seeing this really brings home how much I've beat this engine up. I feel somewhat embarrassed to make this post.

I've had a CHT sensor on #2 from day one. I chose #2 because that's the one that showed the highest temp (by just a few degrees) when testing. Unfortunately that means that #4 could have burned without the gauge showing any problem.

When I get the adapters for the compression tester, I'll see what numbers I get. But at this point I'm resigned to a rebuild. Thankfully, I have the cash coming in to do it - and even upgrade it to FI, which I've wanted to do for years for a few reasons. If I can get away with just a "top-end" build, I think I'll try and tackle it myself.
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