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The mkiv Supra Owners Club

Creamy gunk on oil filler cap


Chris and Alana

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Hi guy's, I was busy on the car and decided to check the oil filler cap (as I do quite regularly) and too my horror it is covered in a creamy gunk. It's normally just got brown oil on it. What could cause this? My first guess is a blown head gasket but I havnt noticed any drop in the coolant level and the temperature gauge has never went over half. Is there something other than a blown head gasket that could cause this?

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Lots of short journeys recently?

 

Coolant and oil levels OK?

 

Clean it off and go for a long drive, get the engine well up to temp - if it's there when you get back you need to worry, if not it's just a bit of moisture causing the problem.

 

Coolant and oil levels are fine and yes it has been doing lots of short journey's recently, how would this cause the gunk (sorry for my lack of knowledge)

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It's moisture in the oil, so anything that could get moisture in the oil could be the culprit :) Loose cap, contaminated oil, a lot of cold starts in the garage trying iron out a problem... Anything spring to mind?

 

-Ian

 

Where can moisture or water enter the engine? The filler cap is one place, a blown head gasket, is there any other's. What other symptoms come with a blown head gasket apart from the gunk? I would just like to rule this out as it will probably be the worst case scenario.

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Coolant and oil levels are fine and yes it has been doing lots of short journey's recently, how would this cause the gunk (sorry for my lack of knowledge)

 

Condensation caused by the engine not fully warming up on the short journeys. This leaves a bit of moisture in the oil, hence the creamy gunk.

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Don't panic, clean it off - go out and enjoy the car this weekend and then check it again when you get back. Very common, especially at this time of year.

 

Ok, will do :) I'll wipe the gunk off use it this weekend and see if it returns. I have the car booked into envy on wednesday for a timing belt change. Is there anything that can be done to check for a break in the head gasket while it's in their hands?

 

Also when I checked it was just on the filler cap, there was no change in the colour of the oil on the dipstick. Is it possable that the seal on the filler cap could be worn allowing moisture through condensation in (there's alot about this time of year)

 

Thanks for the help aswel guy's and very quick, gotta love this forum :thumbs:

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As above, and there's not alot you can do except several long trips to get the oil hot. If you do lots of short journeys, make sure you change the oil very regularly as the moisture reacts with the air in the engine to create an acid which is not good for the seals etc in the engine.

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:( How often do you recommend changing the engine oil if I do lots of short journeys? I currntly use silkolene Pro S 5w40 as recommended by oil man and without turning this into another engine oil thread would it do any harm to use the like's of halfords 5w40 if I change the engine oil alot more often (currently I change approx 5-6000 miles)
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:( How often do you recommend changing the engine oil if I do lots of short journeys? I currntly use silkolene Pro S 5w40 as recommended by oil man and without turning this into another engine oil thread would it do any harm to use the like's of halfords 5w40 if I change the engine oil alot more often (currently I change approx 5-6000 miles)

 

I suppose it depends on how hard you drive it too. I give my some beans but change the oil every 3k miles. Its sat up for the winter now so im just going to put some toyota stuff in until its on the road again then some more silkolene will go back in.

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Get the oil over 100degC so it boils off the water content - a nice cruise at 85mph+ should do that in this weather. On a private test track of course.

 

The short journeys are probably what's causing it. It's not good for a car, most end up with a blown head gasket after a few years, I think because of the constant heat cycling of the engine :shrug:

 

-Ian

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Where can moisture or water enter the engine? The filler cap is one place, a blown head gasket, is there any other's. What other symptoms come with a blown head gasket apart from the gunk? I would just like to rule this out as it will probably be the worst case scenario.

 

To answer your question about how moisture can get into the engine -

 

Combustion gases contain a high degree of water vapour. A small amount of this gas will always find its way past the rings and into the engine (blow-by gasses). If you're only going short journeys (ie not running at 'normal' temps) then this can build up.

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  • 2 weeks later...

Just to update this and for anyone who is interested. I wiped the gunk of the filler cap and took it for a couple good drives (and a couple more short trips to work :( ) and then a 3 hour drive upto Scotland (all in the last week) and there is no more sign of the gunk :) coolant levels etc are all fine as well. Looks like it must have been due to all the short journeys and the cold weather, good news for the engine and my wallet :D Another oil change will be getting done soon as that episode couldnt have been good for it.

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