12 replies to this topic

[brivinci]

Over the last few months, at least, Ive noticed the dreaded milky build up under my oil filler cap. Ive checked the oil at the dip and it always looks good. Coolant levels havent dropped drastically (hard to really measure but never below fins). A ran a leak down test and did not see any bubbles in rad.

I did a test the other night. Cleaned the cap and took the car for a 100 mile, highway/motorway drive. Testing a few other things in prep for a long weekend trip. After driving at 70mph whenever not in traffic (about 30mims of it) I got home and checked the cap the next day. More milkyness! Again, oil and coolant look fine.

I know that cars that arent driven regularly or for long distances can build moisture in the motors but could this still be the case? A few months back I replaced all my coolant lines with mini spares silicone SPi kit. What we pump is the best they sell. Thermo is correct SPi type. Cars temp is perfect...and Im checking from both the original gauge and a electronic VDO with temp sensor in the head by thermostat. Oddly, I have noticed a coolant smell in the car while driving. Heater core has now visuals signs of a leak and no smoke. Checked plugs recently and they all looked as they typically do. None have been steam cleaned nor is there clouds of white smoke.

Wondering what you guys think. Have I missed anything? Pix are of after 100 mile trip. Notice the pools of oil around valves. Not white like cap.

[brivinci]

Oil cap

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[Sprocket]

This can be normal especially if its cold outside. Its just moisture in the air being drawn in through the cap vent, especially if you still have the positive crankcase ventilation system of the SPI still in place.

You know you have a mayo problem when you remove the rocker cover and find it entirely full of mayo

Edited by Sprocket, 07 April 2018 - 07:09 AM.

[Carlos W]

I would remove the rocker cover and clean it all out, check the breathers are clear.

 

Change the oil and filter then keep an eye on oil and coolant levels.

[absx2]

What oil do you use as some do it more than others.

I have noticed the Halfords 20w50 oil seems to do it but the Minispares own brand does not.

[whistler]

Often caused by oil not getting up to temperature due to short runs in winter. If you have a standard oil cooler fitted in colder weather cover up the fins.

[brivinci]

Thanks guys. Rocker is certainly not full of mayo. Just the cap. Ive seen a true head gasket problem before, not on this and not pretty. The temps here have been all over the place. We had an extremely cold winter and just last weekend it was 60f one day, and then snowed 3 the next. Crazy fluctuations.

Ive been running valvoline VR1 20/50 since last rebuild. Its easy to get here in the states and has the extra ZDDP already in it.

Interesting about the SPis positive crank system. The valve cover is an old alloy finned type. Came on my 66 years ago. It has a built in breather pipe on top. I blocked that off as I had nowhere to route it (although I have plans now for an oil separator) and the cap is strange. Ive had to make a makeshift seal for it as it was missing. The whole thing has bothered me but I love the cover. Maybe Ill switch it out for a standard unit and see.

[nicklouse]

I love the use if dreaded. Just use the car as it was designed, with them not being used every day and not getting hot people see things we never saw when were using them everyday to get to work.

[brivinci]

Honestly, you see mayo in your oil, its dreaded. At least a sign of not so great things. Obviously moisture gets into cars and not driving it daily causes this but it never hurts to ask, right? Set my mind at ease. Mostly because I have owned this car for about 15 years and have never seen this happen before. That and there is a whiff of coolant in the cabin.

[Sprocket]

 Ive had to make a makeshift seal for it as it was missing. The whole thing has bothered me but I love the cover. Maybe Ill switch it out for a standard unit and see.

I'd suggest your makeshift seal is not working properly

 

It doesn't necessarily have to be cold for this to happen. humid air will give up the moisture when its pressure drops, at the same time the temperature drops. If the filler cap has a small hole in it, this will be the point where the moisture will build up. In this case I suspect your cap doesn't have a small hole, but rather the seal is leaking. With the positive crankcase ventilation working as you cruise along, the engine crankcase is in a partial vacuum, more so if there is no real vent in the filler cap. This is what creates the pressure drop and subsequently causes the moisture build up in that localised area as the air leaks past the seal.

 

If you look at the original tin cover filler cap, it is vented and contains a compressed wire filter. This cap allows a greater flow of air in or out of the crankcase, prevents a lower than normal crankcase vacuum, thus would normally prevent the build up of Mayo in most driving conditions. If you can fit some sort of gauge to measure crankcase pressures (vacuum in some instances) it might show that you could be pulling a significant vacuum under certain driving conditions.

 

Would be worthwhile pulling the breather hoses and looking inside those too, the ones from the transfer case, the timing gear case and the large one onto the throttle body.

[brivinci]

My makeshift seal is totally not sealing right. The cap doesnt have a vent in it as the original Rober unit does. This cover was made by J.V.M. Of England, from maybe the late 60s or 70s. My 66 Cooper came with it as well as a few SPQR parts from the period this cover has a breather pipe that screws to the top. I actually used to have that breather open and facing backwards. It would puff out a bit of oily air straight onto one of the air boxes closure clips. Ive been meaning to pipe it into the cars breather system but hadnt...so I plugged it off. That was more recently...and probably about when I noticed the mayo build up starting. Funny that!!

So, if I were to reopen that breather, could I pipe it into the cars ststem? My SPi has that metal pipes that wrap around rhe back of the rocker cover. I could T off one of the pipes and run it all together. Would that work??

[brivinci]

I piped the rocker covers breather into the rest of the cars breather system and its cured the issue. Makes total sense now. The cap is not vented so the breather HAS to be open to vent. Thanks all.

[brivinci]

Using the power of the interwebs I was able to discover that the cap used on this rocker was made in England and the company is still producing them. The caps I mean, not the rocker cover. A vented version of the cap was used on triumph and BSA petrol tanks. I bought a new cork seal for 3 bucks and now I’m TOTALLY back in business!