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MG MGB Technical - White Paste on oil filler cap

Hello all,
I just changed the oil in my 78 B the other day and was unpleasently suprised to see some white milkey paste on the bottom of the oil filler cap. The engine was gone through about 2500 miles ago with new cam(piper270), pistons, multiangle valve job with new head gasket sourced from Bob Ford at Britec. The car is mostly used on short trips and the oil drained during the oil change did not have any water/antifreeze in it nor did the coolant appear to have any oil in it when checked. Is this paste coming from the short trips or a sign of a blown head gasket? The engine runs very well and uses little oil and is loosing no coolant. Is it time for a Payen head gasket or take longer trips to heat the motor up more ?
R Slice

Maybe do a compression test to set your mind at ease but it sounds like emulsified oil from short trips which would disappear with a long run. It forms there as that's the coolest part of the engine, and used to be very common before modern engines which run hotter.
Rich

R, if there was no white paste that came out during your oil change, it is most likely just condensation from inside the engine being boiled off to the breather. This is more common with aluminum block engines, but happens in all engines. If your car is subject to cold nights and warm days (anytime you'll see dew on the grass) You have the possibility of this happening. Like I said, if there wasn't water or oil foam coming out the instant you pulled the drain plug, it's probably nothing.

If you want to check for a blown head gasket, there is a kit you can purchase at napa, or probably other auto parts stores that sits on your radiator filler and tests for exhaust gasses in the coolant. The tester is filled with yellow fluid that turns blue in the presence of CO. It is very effective, and much cheaper than tearing down the top end.
Jeff Schlemmer

I think your only problem is.
"The car is mostly used on short trips"
Change oil more often on any vehicle that is used on short runs, base the change time, not miles. That used to be a common problem long before aluminum engines.
Clifton
Clifton Gordon

Seen this a lot. Foird V* dipsticks mounted in the fromt of the engine were the worst cluprit and probably led to more unneeded work than any other engine part. Drive the car to normal operating temperature. As Jeff said above: it's most likely condendation. Water is a by-product of the combustion process and not getting the engine to normal operating temp never allows the water time enough to evaporate from the oil OR the exhaust system. It's a fun car. Drive it.
Tom

In the shop for years, we used to see this when a certain brand of oil was used.
Namely, starts with a 'P'
Jest don't a wanna' get in trouble.
Safety Fast
Dwight
Dwight McCullough

Now that you mention it Dwight the C brand was the one which used to cause the problem in the UK. However most of it has been said except, make sure that the breathing system is clean and in good order and you bshouldn't really have much of a problem with the B series.
Iain MacKintosh

Thanks for the input, that is what I thought just wanted to make sure. BTW I use Casteroil GTX 20W50 in both my LBC's.
thanks Paul
R Slice

It isn't getting hot enough. Used to see that in sub zero weather in MT on my Ford pu unless I blocked the radiator with cardboard.
Bill Haglan

Have you got a radiator blind?
Do you have an oil cooler thermostat?
Try making up a cover out of heavy cloth or leather that can be fitted over the oil cooler.
I tapped a temperature sensor into the bolt that retains the pipe from the oil filter housing to the rear of the block (on an MGA). You will be surprised at how long the oil takes to warm up, much longer than the water warm up, if it ever warms up at all.
Is your breather extraction system OK?

Mick
Mick Anderson

Mr Slice
What temp thermostat are you running? In the winter it should be at least a 180 degree thermostat. In my '67 gt with alloy head I run a 195 thermostat summer and winter with a stock 7lbs pressure cap. A little water wetter type product and about 1/3 antifreeze. No problem on the hottest of days and steepest of grades.

It sounds like your running a 160 thermostat and running short trips in the cool season. Condensation can add up real quickly. A by product of combustion is moisture. It takes some heat to boil it off it as it condenses. It is best to prevent it from condensing in the engine in the first place with a higher temp thermostat.

Barry
Barry Parkinson

Barry, Mick & Bill,
I think you may have hit the nail on the head. I have a 180 thermostat on it since the rebuild, this is the first winter that I have driven the B and the temp gauge only moves about a quater inch above the cold mark unless it is sitting idling for a extended period of time. This was a good thing during the hot summers in SC but not in the winter. I also have a electric fan but it is adjusted to come on when the gauge gets to the middle. It is begining to warm up in SC so I think that I will install a blind in front of the radiater for now and install a 195 thermostat next fall. BTW the radiator, water pump hoses and t-stat were new when the engine was gone through and it has no oil cooler installed.
thanks again, Paul
R Slice

Go ahead and put the 195ºF tstat in now and run it all year. Remember, a thermostat can't keep an engine from running too hot. It only prevents the engine from running too cold. A blind in front of the radiator can be dangerous in that if your car starts to overheat, you may not be in a position to pull off the road and remove it.

Your engine will run more efficiently (i.e. better mileage and more power) if you run it hotter. Peter Burgess, the acknowledged guru of hot-rod MGB engines, says the ideal tstat is 88ºC -- which around 195ºF. Also put in a thermostat blanking sleeve available from Moss & other vendors. Here's an explanation of why:
http://mgaguru.com/mgtech/cooling/cool_103.htm
(Start reading and click the little green right arrow at the bottom to go to the subsequent pages)

Thanks to Bob M. for pointing out the above info!

Also keep in mind that it's not required that your temp guage remain rock-steady on 'N' all the time. Mine runs anywhere from just above 'N' to just below 'H' with no worries. It's not overheating until it boils over and/or starts running poorly from the heat.
Rob Edwards

I noted that the engine temperature would sometimes go quite high, before it settled down to the 190 plus range. I drilled a hole (less than a 1/4") in the stainless steel diaphram holding the thermostat, to allow water (at low volume) to flow even when the thermostat is closed.
It eliminated the temp spike on warming up and appears to have minimal effect on the temp regulation. Going down a long grade the temp will temporarily drop, and it probably takes a little longer to reach full operating temperature than it would otherwise.
By the way my '67 mechanical temperature guage which peaks at 212 degrees f runs at an indicated 200 f. Going up steep grades in lower gears and driving in a sporting manner on warm days, the temp will approach the top of the guage. With a water wetter type additive (version from Kragen) and 1/3 to 40% antifreeze and only a 7 lbs stock cap I don't lose any water. I have installed a water bottle to catch and return the overflow. I virtually never have to add fluid. The alloy head probably helps in cooling too.
Barry
Barry Parkinson

Based on advice I found on the internet, I drilled a 1/8" hole in a thermostat. I found that on cold days, the engine never reached regulated temperature. Switching to a thermostat without the hole, it reaches operating temp in just a few miles, even with ambient temps in the low 20s. I guess all this just proves YMMV! ;-)
Rob Edwards

190-195 degree thermostat works great. I use one all year long and the summers canbe fairly hot around here (95-100 F) and have not had a problem.

Benefits are a heater that functions in the winter time and a noticeably better feel to engine running.
Richard Smith 1

If you get this 'mayonnaise' on an MGB then either the breather system isn't functioning or you simply aren't driving it for long enough each time you start it in cold weather. There is lots of plumbing associated with the breather on a US 78. Basically the carb sucks on the front tappet chest cover of the block, the port on the back of the rocker cover sucks on the charcoal canister, the canister sucks on the anti-run-on valve, and the valve sucks in fresh air. Any blockage in that path could cause the problem.
Paul Hunt

This thread was discussed between 11/03/2005 and 18/03/2005

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