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Oil on the underside - but where from?

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AlFresco

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This topic has probably been covered somewhere else so please direct me if you can.

Getting quite a bit of oil film/droplets underneath CW the 1098CG Sprite. The engine and g/box have recently been rebuilt and so I suspected need for retightening of sump bolts or similar, rather than failing seals. The bolts have been nipped up and happy they are not the source.

Appears to forward of the engine rear seal/'box front seal area. Local mechanic who knows A-series inside out (Mini specialist) suggested maybe the block side cover plate with the breather tube might be encouraging oil to flow down the tube due to a damaged/modified baffle. Here's a photo of it - I don't think his suggestion is likely given the how close the baffle is to the plate's inside surface. Is that the normal appearance of this part?
Cover plate baffle query.jpg
Other current suspects include the rocker cover oil filler cap and the little tube off the top of the rocker cover that is meant to go to the back of the air filter housing on the front carb. Its just open at the moment. Is positive crankcase pressure a possible factor bearing in mind engine is practically new? Oil pressure is consistent and strong.
I've also heard of oil-bearing fumes being a potential source if there is no oil scavenging - I have no PCV valves that I can see and its essentially an open system.

There's enough oil appearing to make it hard to just wipe off and then try and locate the source after a run.
Cheers
 
They make a UV dye that you put in your oil to help find leaks. It takes special glasses a light but they sell those too. You should be able to buy these from your local parts store.
 
If it's forward of the main seal (where mine still has a leak), I'd be inclined to think valve cover gasket. When I went to replace the head gasket on my 1275, after I pulled the carbs and manifolds off, I found the whole left side of the block was coated in oil.

One other possibility -- drain plug isn't tightened up all the way, or possibly worn? I found I had a drip from the plug when I crawled under the car to replace the exhaust.
 
If you have a 1098 they need the timing cover vent connected to a Flying Saucer type PCV valve and IIRC to the valve cover, 1275's connect to intake manifold at base if carbs. The A Series engine needs to negative crankcase pressure controlled via a small 1/16" hole in the PCV Valve. Without it, your leak is coming from the rear scroll seal on the back if the engine more than likely. Look in the MOSS catalog all hardware parts & pieces are available or Colin Dodd down in Oz can take care of you.
 
Many thanks for the great suggestions/information. I've got something to work with
Chrs
 
Jim_Gruber said:
If you have a 1098 they need the timing cover vent connected to a Flying Saucer type PCV valve and IIRC to the valve cover, 1275's connect to intake manifold at base if carbs. The A Series engine needs to negative crankcase pressure controlled via a small 1/16" hole in the PCV Valve. Without it, your leak is coming from the rear scroll seal on the back if the engine more than likely. Look in the MOSS catalog all hardware parts & pieces are available or Colin Dodd down in Oz can take care of you.
Click to expand...

Jim, his side cover vent indicates he has the early 1098. The 10CG engine which doesn't have a PCV system but just an open vent tube to atmosphere. I would personally try to open the smashed steel shield inside the side cover that is restricting draft from the tube and reconnect the hose to the air cleaner first to see if that helps. Stand's to reason that if the crank case pressure build's up its probably going to push oil past the crank scroll seal.

Kurt.
 
OK, thanks Kurt. So what you're saying is that the steel shield (I called a baffle) should not look like it does but rather should be open to encourage air/fume flow. Has anyone got an image of what it should look like?

Tube to back of air filter is a bit more involved as the replacement filter housings have no hole, but can do if you think worthwhile. Is this a more active method of creating negative environment in the engine eg. by employing a vacuum? (through venturi effect?) If thats the case I can see the value if it acts on the crankcase pressure as well.
 
Kurt
you are indeed correct. Didn't see the picture reading this on my phone. Same principle would apply however if venting from timing chain cover or side vent. Controlled negative crankcase pressure. When I first got Bugsy my 68 with. '66 1098, the owner had removed PCV and plugged connecting hoses. Spark plug stuffed in one hose and a 4" 3/8 extension in the other. Finally got the engine started and thought I bought the Exxon Valdez. In < 5 minutes running I had a foot wide puddle under the rear of the engine. After cogitating I realized what DPO had done, added PCV Valve and drove that engine for another 12 years. Bugsy still marked his spot whenever he was parked with 4-5 drops of oil but cardboard on the garage floor under the rear of engine is easily replaceable.

Now the side vent is part of the Spridget Chassis self oiling system. A standard feature BTW on any BL Vehicle.
 
Well, I may be wrong but its been my understanding that the draft tube is supposed to create a negative pressure as you move along and the valve cover vent is primarily to get rid of any positive pressure that builds up under hard acceleration that might accumulate at the top end. Don't know how well that worked but do know the scroll seal is a tricky common leakage problem. The inside of the sidecover vent is obviously bent so would definitely start there. Can't help on pic's.

Kurt.
 
Jim_Gruber said:
Kurt
After cogitating I realized what DPO had done, added PCV Valve and drove that engine for another 12 years. Bugsy still marked his spot whenever he was parked with 4-5 drops of oil but cardboard on the garage floor under the rear of engine is easily replaceable.

Now the side vent is part of the Spridget Chassis self oiling system. A standard feature BTW on any BL Vehicle.
Click to expand...
:highly_amused:

Jim, where did you place the PCV valve and what does it look like - is it a standard part for the later Spridgets and under what description would I order it?
 
Page 25 of the new Moss catalog. Now since I don't own that Sprite anymore we're going to need some help to figure out hole to plumb the other side of the PCV valve. I can't remember how things were plumbed into the intake manifold but believe there was a fitting that attached directly to the intake manifold. My 1275 uses a Y fitting that splits off two hoses that go to a nipple on the base of the carbs and dump into the intake manifold. Look and see if you have a plugged fitting on the center of the intake manifold.
 
nomad said:
Well, I may be wrong but its been my understanding that the draft tube is supposed to create a negative pressure as you move along and the valve cover vent is primarily to get rid of any positive pressure that builds up under hard acceleration that might accumulate at the top end. Don't know how well that worked but do know the scroll seal is a tricky common leakage problem. The inside of the sidecover vent is obviously bent so would definitely start there. Can't help on pic's.

Kurt.
Click to expand...

Correct. However, with most machinists these days being unfamiliar with the scroll seal, even many rebuilt engines have not had this little detail handled properly. In addition, and sometimes a result of that, all the correct efforts can still result in a moderate to serious leak. When all else fails, my rear seal kit will cure the problem.

More explained here:

https://gerardsgarage.com/Garage/Tech/SealKit/SealKit.htm

WP_000735_4x3.jpg
 
Anybody with an older 1098 want to pull off their front side plate and take a photo of what the vent opening looks like from inside?!:encouragement::angel2:
 
I know it is filled with steel wool
 
I'd take a guess at it and open it up some with a screw driver. It is likely supposed to have some course steel wool as a strainer but I'm not sure where it would go. How about your valve cover vent? It should be open to someplace as well?

Kurt.
 
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