6 replies to this topic

[Jacksdad]

 Tappet chest cover..jpg   69.4K   29 downloads

Trying to stop Jacks mini from leaking gallons of the oily stuff over the drive I`ve identified two main leaks, one from the timing chain cover the other from the tappet chest cover. Timing chain cover is easy to do but upon removal of the tappet covers one had a good rubber gasket the other had a load of goo!! But my main question is about the breather outlet, see photo. Is that standard to have a welded washer to the outlet or is it a mod? If a mod, why? What does it achieve? Thanks, Steve.

[jaydee]

Never seen one like that, i bet it should drain all the oil in no time
Thats the part and how it should look:
http://minispares.co...ck/12A1212.aspx
And heres the gasket:
http://minispares.co...ts/12A1175.aspx

[Jacksdad]

Resurecting this topic as I still haven`t fully cured the leak! Oil is still blowing out around the dipstick collar where it sits in the block. I`m convinced it`s to do with crankcase pressure and that the "modified" tappet chest cover (see original post) is to blame however I`m not 100% sure as I don`t know whether it should be like it is!!!

So can anyone tell me catergorically if the tappet chest cover should have the washer welded on the outlet?? If you happen to have one in your garage a photo would be appreciated or any comments if you have or have had this issue.

Thanks

Steve.

[dklawson]

I would not assume that oil issues at the dipstick are associated with problems on the tappet covers. While the tappet cover can have a vent attached, even one restricted by a washer should allow sufficient flow of gasses. If it will make you feel better, by all means open the hole in the washer up to match the size of the tubing nipple that is welded on the outside.

I suggest that the real issue is blow-by from the piston rings. I would perform a compression test followed by a leak-down test to determine the extent of the blow-by. The leak-down test will really highlight this and would be the preferred test if you have access to an air compressor. If you discover the problem is blow-by there is no fix short of an engine rebuild.

[Jacksdad]

Thanks for the info Doug. By "blow-by" I presume you mean compression leakage at the rings causing pressure to build up in the sump thus blowing oil out thru` the dipstick aperture?? I do have a compressor, again I presume a leak down is to pressurize the cylinder using compressed air and measure the resulting drop in pressure?. I can also conduct wet and dry compression tests, would that achieve the same as a blow by?? Thanks again. Steve.

[ArneBrys]

Your assumptions are correct.
The benefit of using a leak-down tester is that the engine does not run during testing.
You will just be pressurizing the combustion changer and it is more easy to determine where the air is leaking to as you can usually hear ear from a dip stick/carburetor/exhaust if the rings/inlet valves/exhaust valves are leaking.
You can get a very similar diagnosis by comparing a wet and dry compression test.

[dklawson]

You can buy leak-down testers but you can also make your own (which is what I did). Information on how to make your own can be found in the link below.
http://www.motorcycl...t/leakdown.html
One clarification. The web page author refers to one component as a damper valve. That is not a good description. It is really a 1mm flow restriction orifice.

All of the parts can be made from bits you may already have... an old spark plug, an air pressure regulator, some pipe nipples... One IMPORTANT change to make to the schematic shown in the link is to incorporate a second pressure gauge. Most regulators will have ports into which you can thread a gauge into. Install a gauge there to show the output pressure from the regulator. The second gauge (shown in the schematic linked above) is shown on the other side of the orifice. If you set the regulator output to 100 PSI, the second gauge after the orifice will show a lower value and this is often discussed as a "percentage" of leakage (for example, 100 PSI out of the regulator, 80 PSI displayed on the second gauge would be "20%" leakage). It's not really a percentage but supplying 100 PSI out of the regulator provides a method for discussing the leak down in more or less standardized numbers. The actual value doesn't matter unless it is exceptionally low.

As Arne said, the benefit of a leak-down test is that you can hear where the problem is to quickly locate the source of engine problems. They can also find problems that a compression tester does not indicate. For example, on a non-Mini car I had terrible running problems and no power. Compression tests showed a very uniform but low pressure of about 100 PSI. A leak-down test revealed immediately that I had a leak into the cooling water jacket, bad blow-by on two cylinders, and leaky valves on the other two. If you have an air compressor, the leak-down test will quickly help locate problems that a compression test can only hint at.