Mayo under oil filler cap.

Burny

Joined
Jul 2, 2012
Messages
55
Location
North Yorkshire
Bike
1991 st1100
Hi
I've had this problem for a while now and while it does not appear to be affecting the bikes performance it's one of those things that just gets hold and annoys the living daylights out of me. My first thought was head gasket. There's a little white smoke on startup but it's coming out of both pipes in equal amounts so I'm putting that down to choke/condensation. Most of my riding is done in short stints to work and back (2 miles or so) so I thought that it may be down to that. Recently had an oil and filter change so I cleaned the mayo out of the cap and took it for a good hard blast of about 25 miles or so and guess what? more mayo. She's not using a drop of water and the oil looks good and clear. The only thing I can think of is that when I took the oil filler cap off I noticed that the sealing washer is missing. Could this be affecting it?
 
It sounds like you're getting coolant into the crank case. I just replaced the engine on my truck for a cracked head that was doing the same thing. Keep a close eye on your coolant level and check your oil frequently.
 
JoeP said:
It sounds like you're getting coolant into the crank case. I just replaced the engine on my truck for a cracked head that was doing the same thing. Keep a close eye on your coolant level and check your oil frequently.
Click to expand...

+1
Milky oil is definite sign of possible water intrusion. Do you ride in rain or wash the bike frequently? That would be the only way water could get in through the oil cap, otherwise its coming from your cooling system... somewhere.
 
That's what I can't figure out. It's not using any water and the oil is clear as a bell. I was kind of hoping that the lack of a seal was sucking cold damp air in resulting in the mayo. Although I suppose there will be positive pressure in the crank case.
 
Oh dear, sounds like water intrusion into the crankcase from somewhere.... most likely a head gasket as this is a classic symptom....

I would do an oil drain to check for water in the bottom of the oil pan....

Compression test would also be a must..... but I guess those heads need to come off, you may only need to take one off but it isn't a five minute job.... the compression test may give a clue as to which side....

I guess it is possible that water could be getting in another way, but that mayo is a sure sign it is coming in....
 
Rotary rx-7s do that normally.

It's condensation mixing with the oil .

Possibly exacerbated by short trips.

If your oil looks good when you drain it, I wouldn't worry about it .
 
Yep, the short trips are killing it. Been there. Let it warm up to the three bars before getting on it. Try to ride for at least 15 minutes before shutting off.
The only cure is to ride more !! Get the moisture "burned" out and keep it that way.
You should be able to see the milky , foamy oil in the site glass while it idles after a short ride.
 
LetErBuck said:
Yep, the short trips are killing it. Been there. Let it warm up to the three bars before getting on it. Try to ride for at least 15 minutes before shutting off.
The only cure is to ride more !! Get the moisture "burned" out and keep it that way.
You should be able to see the milky , foamy oil in the site glass while it idles after a short ride.
Click to expand...

1100's dont have bars on the Temp Gauge. My needle barely gets into normal range unless stuck in traffic. I agree that you've got a coolant leak somewhere.
 
Burny-How are you checking the coolant level? Are you looking at the plastic over flow jug level? The jug will catch the over flow from the radiator but will not empty back into the system if there is a leak in the hose. Usually the hose cracks about 1/2" from the radiator cap. It makes a sharp bend there. If it hasn't been done before, you can cut the hose an inch or so back and stick it back on. You will need to put a clamp back on it. If that takes care of the problem, I would install a whole new piece of hose on it. It's probably about 6' long.
 
In high school my boss had a New Yorker, he drove 2 miles to work and back
When I would check his oil there was always mayo look on oil cap, he would
Give me car for weekend to put miles on it
 
IMHO, callin' BS on the coolant leak. Combination of where you live and the extremely short commute bout tells the whole story. Oil clean looking in sight glass as you say definitely rules out any leak. That short commute and shutting off IS drawing in the moisture as it cools down. Your gonna have to do more ridin', and for longer periods of time to eliminate your issue.
 
Hi Ron
I have already fixed the overflow hose as it was perished as you described. I am checking the coolant level both in the overflow bottle and just to make sure I also checked the radiator.
 
If the oil is clear and the coolant itself isn't milky I would say it is from condensation. The short distance riding would exacerbate that problem. I guess you just need to ride more.

If a head gasket was leaking you would have milk for oil, not just milky stuff on the filler cap.

Firstpeke said:
Oh dear, sounds like water intrusion into the crankcase from somewhere.... most likely a head gasket as this is a classic symptom....

I would do an oil drain to check for water in the bottom of the oil pan....

Compression test would also be a must..... but I guess those heads need to come off, you may only need to take one off but it isn't a five minute job.... the compression test may give a clue as to which side....

I guess it is possible that water could be getting in another way, but that mayo is a sure sign it is coming in....
Click to expand...
 
I'd still drain the oil and check for coolant in the bottom of the pan.......

I haven't seen mayo in a filler cap for years on a modern engine running modern oil, either synth or dino...... unless the gasket's gone.

Compression test, cooling system pressure test if you can get one....... the ST warms up pretty quickly unless the thermostat is stuck open.....

You won't see water in the oil level window it goes to the bottom of the pan....

Before my Pan was totalled, going to work I did 2 miles, ferry, then 5 miles..... never saw a hint of condensation..... could have run that oil much longer than I did but always changed at around 5000 miles, give or take a 1000 depending on planned use...
 
Quick update. Cleaned loads of mayo out from under cap then took her for a good long blast. Let her cool down when I got home and then checked the cap again.......................mayo present but not very much at all. In fact very, very little. Hopefully it's just condensation. Fingers crossed.
 
You could pressure test the cooling system. If that looks OK, I would say those short trips are causing the mayo to form. I see that somewhat on one of my cars. Take that ST1100 out for a nice long high speed ride and blow out the carbon and evaporate any condensation in the crankcase.
 
Jim Van said:
You could pressure test the cooling system. If that looks OK, I would say those short trips are causing the mayo to form. I see that somewhat on one of my cars. Take that ST1100 out for a nice long high speed ride and blow out the carbon and evaporate any condensation in the crankcase.
Click to expand...

You could also do a cylinder leak down test fairly easily. That would give you a definitive answer.
 
If the leakdown test failed, you wouldn't know if you had a bad valve, bad rings , or a leak into the coolant passage. A cooling pressure test would pin-point a coolant leak that could be causing the "mayo" to form.
 
To put your mind at ease (or give you nightmares) the next time you drain the oil have an oil sample taken and send to a reputable lab for a glycol test. Blackstone labs do this for a relatively small fee and it will give you an accurate analysis of your engines condition. I had the same symptom on my Tacoma, but only in the wintertime here in Illinois and they put my mind at ease and provided a complete analysis of all the wear metals and viscosity of my used oil.
 
You must log in or register to reply here.
Back
Top Bottom