The Stovebolt Site Forums The Shop Area Engine Shop Milky oil at draft tube

...pic...

Just noticed this, have not seen it before.
Cool mornings, warm afternoons.

Did not notice any milky oil on dip stick.

Condensation? or should I investigate more?
thank you for any suggestions on what to look for.

condensation - not running long enough

Bill

I took that pic after coming home from work today in the truck.

Its about a 25 minute drive reaching highway speeds of up to 45-50 MPH for a short streach.

The engine temp was 150 degrees

when you say not running long enough are you meaning I should warm the truck longer before I drive it?

Is that 150 degrees on the temp gauge? If so, sounds like it's time for a thermostat. Not running long enough, or hot enough to burn the condensation out of the oil is the probable cause. Engine temp should be 180 degrees or so

It was 150 at the gauge and I verified it with digital laser deal.

I've been using a 160 t-sat the last 2 years summer and winter.
Maybe I'll install a 180.
My truck has a car 235 in it. I think that's why the 160 was in it.

the stat should set the minimum temp that it runs, if it's a 160 and it stays 150, the stat is bad - but car or truck, it should have a 180 when the weather cools down, maybe a 160 in high summer

Bill

Thank you
I have a 180 t-stat in the garage and will install it.

I have had that stuff hanging out at the oil fill hole after 2 or three hours at high way speed. I was using a 195 degree thermostat at the time. I'm not sure how cold you get down there, but it was wintertime when I was driving through nevada and this is when I noticed this. All I know is it takes a long time to get rid of it all, but mostly it is just hanging out where there isn't a lot of engine heat, the important part clears up pretty quickly. But it was bad enough that when I took off the valve cover there were flakes of rust that had fell off the inside of the valve cover. Which is mostly why I got an aluminum valve cover, it isn't really affected by the moisture. Yes it will corrode, but I don't think it will be to the extent of flaking pieces off into the engine.

thanks brokenhead
It was low 70's yesterday when I drove home. unusually warm.

Ok
I'm a little embarrassed to ask this but here goes
this is the new 180 stat.

It looks like it has a little check valve built into to it, my guess its to purge air. the 160 thats installed right now has a 1/8 hole drilled into it.

is the side your seeing in the pic the top?
spring side down.

that little check valve thing is throwing me off and I haven't even had any holiday cheer yet!

That is to help prevent air pockets in the system when you are filling the coolant.

No need to drill the 1/8" hole with that type of t stat.

thanks
but is that the top when installed in the pic?

the little valve will be closed if it is

Yes that is the top. I can't explain how it works but it does.

Thanks!

the little check valve thing is the DELUXE model....

Hate to dig up an old thread but along with the colder evening temps I've noticed this same milky deposit on my oil fill cap. I pulled the valve cover tonight and noticed a coating of it around the fill hole. Oddly it's just around the fill hole.
A search brought me to this thread.....
My 1st thought was condensation and it's looking like thats what it is. It wasn't anywhere else in the head or valve cover and theres none present on the dip stick. I haven't had to add any coolant since i put it back together..
I didn't notice this until the weather turned cooler. My rear main leaks so I'm adding alittle oil regularly...
The engine is a 49 216 w/a 160 thermostat. I generally run it for an hr at a time and the temp never reaches 180. I guesstimate it reaches perhaps 170.
I'm now wondering if I should go to a 180.
Has a 180 done away w/the condensation with those of you in this thread w/similar symptoms?

One additional question. I'm thinking of going to a vented oil fill cap and plugging the 3 vent slots in the valve cover to try and minimize the oily film that accumilates on the valve cover, is this the venting setup on the 235's?

Dave

Best way to keep condensation out is to make sure the engine gets up to temp. Its a rare occasion that I start up one of my vehicles and not let it warm up to temperature even if its just to back one out of the shop...I let it run till temp gets up. Condensation will also rust out your exhaust system.

Personally I see no reason you can't use a vent cap plug the slots. That's what GM did anyway on a lot of engines. Just as long as it can BREATHE. ...others may feel differently.

Even in Tennessee it should reach temperature. Perhaps your gauge is wrong. Check the temp by putting a thermometer in the radiator neck, or if you have an infra red light check the top of the tank where the return water is coming back in. If you have to put a piece of cardboard in front of the radiator for a while to see if that will help it get up to temp.

Yes

The 180 stat took care of the milky deposits from the road draft tube for me.
My 54 235 has the slots in the cover.

You could always get a later 235 cover with the vent filler

There's no really good way to keep atmospheric moisture out of your crankcase on a draft tube engine. Even after running the truck down the road, when the engine cools down, it just draws the moisture back in. Maybe try to convert to a PCV system would help burn up the moisture faster.

I had the valve cover with slots, (which I squooshed and brazed shut in an attempt to cut down on an imagined dust infiltration problem) and a vented fill cap. My experience with the same truck for the last 30 years is when it gets cold out there will be milky oil around the vent, don't squoosh the slots, that will make it even worse. When I was driving from sandiego to Montana, in the morning it would be clear, then the first fillup it would have the milky oil around the filler cap, the second fillup would be less, and finally sometime after noon, it would be almost completely clear, but it took at least 4 hours. But it was nearly strictly in the fill cap area. And since that engine lasted some 31 years, I wouldn't worry about it.

I was taught that engines should run at 180 degrees. Any less and the clearances are tight causing things to wear out faster.

Mike B

I would check to see if the draft tube is restricted. It is designed to have fumes sucked out of the crankcase at higher speeds. The air supply to replace this action is replenished through the slots in the valve cover or a vented fill cap. Any condensation in the system will likely move to the highest point in the engine (the valve cover). If you don't have good flow through the draft tube, the condensation will not be completely purged. I would also suggest that you pull your spark plugs and see if any of them are much cleaner than the rest of them which would indicate a cracked head or bad head gasket (small coolant leak with steam clean the plug).

Been following this Gus for a few days now. Sounds to me like
you might have some blow by. Lots of moisture from the
combustion process and if it's leaking past the rings it could
be your moisture problem. I'm sure by now that every one
understands that oil and water emulsion is what creates the
milky scum that we see.
For the first five or six thousand miles I put on my '50, 216 I
too had the milky scum at the draft tube. The engine ran fine
cept for using a lot of oil, (bout a qt. every hundred or so
miles). I even went so far as to hang a diaper on it, actually
it was a catch can that I taped to the tube to catch the muck
and keep it off the floor.
I rebuilt the engine a few thousand miles ago, bored, new
pistons, ground crank, insert rods, balanced, full head rework
and all. Haven't used ANY oil yet between oil changes and
haven't seen a spot of the muck on the floor or draft tube
since then. I've driven it in hot humid and cold freezing
weather for a couple of years now and have always kept a
180° stat in it.

Denny Graham
Sandwich, IL

Lots a good information here

I started this thread last year in November
When I switched to the 180 stat the milky deposits ended.

When the cool temps hit again ill monitor and see if happens again this year.

I've put 9600 miles since I started driving the truck again in 2010
Not sure what work has been done on the 235,
it is burning some oil but is running strong and am averaging 16 mpg.

Ditto on the good info.
I've temporarily plugged up the three vent slots on the valve cover and added the new vented oil cap. Took it out for a 30 mile round trip.
There was no milky sludge afterwards so I'm pretty confident it's definitely condensation.
This 216 does have blowby and that no doubt is contributing.
I'm hopeful that routing all the blowby and any heat generated in the valve cover out the one single outlet will help retain more heat & help clean it out. And in the process minimize the buildup at the highest point in the engine. I thought it unusual that the buildup was around the front of the valve cover around the filler hole.
I haven't ruled out going w/a 180 thermo but this engine had a 160 in it and I'm pretty sure thats what has been run in it since new.... I'm the 2nd owner and knew the original owner.
I'll be monitoring and will update also.
Dave

I do know that on the cover I had brazed the slots shut on, rusted so bad in the back where the moisture couldn't get out because I brazed the slots shut. That it was coming off in chunks, up front where the vented fill cap was it was a whole lot better. So I wouldn't automatically assume everything is fine in there, just because you can't see it.

Personally, if you aren't a purist, just pull the road draft tube out, and install a pcv system in. No oil dripping out, no worry about what color it is. With pcv, you get all of the contaminants (airborne) out of the bottom of the engine. I have no idea if it prolongs engine life, but never again will you have a dirt magnet that drips oil out of it on your truck. Its on my website.

Pulled the draft tube and it was just about fully clogged up w/60+ yrs of hardened crud.
I decided to go w/a PCV mounted in a freeze out plug installed in the draft tube hole. That mod seems to work very well.
I changed the oil to a thinner grade also (10w30).
Unfortunately after 2 long shakedown cruises, both of which were well over an hr each, a checkout the next morning showed there was new milky crud around the oil fill.
In the cruises the engine temps never got to 180, I'll guesstimate a max of 160-165. The outside temps are cooler.
Looks like the next step is to go w/a 180 thermostat.
Funny, I was really likeing the engine running so cool.....
Dave

Running cool isn't the most efficient way to run that engine
Dave. I would only run that cool of a stat if I were
stationed in the middle of the desert or south of the border.
180° to 200° on you temp gauge is where you will get the best
performance and fuel economy.
These Stovebolt sixes will not have muck in the oil unless there
is an excess of moisture getting into the crankcase. Even the
extremely small amount of condensation that may accumulate when
the engine is cold will be boiled out as the oil comes up to temp.
Look to wear in the cylinder, worn rings, valve guides, a
cracked head or leaking head gasket, that's most likely where
your access moisture is coming from.
The machine that we are dealing with here was designed long
before I was born, which was at the beginning of the big war,
and remained with the same basic design with minor changes till
1962. To expect it to perform like a modern day engine is
wishful thinking. They will drip oil a little oil, they will
not get good fuel mileage, they will run nosier than your 2014
Silverado, they will stink the garage up over night, they will
need a tune up every 5,000 miles, they will need frequent oil
changes.
Nope, taint like the new engines and one is going to be
disappointed if they expect it to act like one.
Chime in here PreDave, you've worked on plenty of these old
timers. You think there is such a thing as a drip free
Stovebolt six half worn out parked in anyone's garage???

Denny Graham
Sandwich, IL

I would pull the valve cover off. If there is milky crap under there, you can be pretty sure that you are getting coolant in the oil from a cracked head, cylinder or head gasket or you have . As for the operating temp, I drove GMCs of this vintage in Texas heat when we were still using them in the business. We used 180 thermostats year round. A colder thermostat won't keep them from overheating in the radiator is stopped up. It just takes a little longer for a boil over.

Good info.
After trying all my FLAPS, ordered a 180 thermostat & gasket, should have it installed by the weekend.
The 160 themostat I'm currently running is the same one that was in it when I tore the topend down. It bench tested good so I cleaned it up & reused it.
Since I didn't have any condensation problems until the weather turned cold I'm still holding out on it just being condensation.
If this last fix no workie, then deeper I'll go.....

The head was rebuilt and all gaskets are new. I've got maybe 1k miles on the engine since I got it running but then again, it sat for 44 yrs before hand so something else could have failed since the weather change also.
Other than the valves being louder than I like, this old 216 is running pretty strong on all 6 cylinders. The more I run it the better it runs. Blowby has decreased to acceptable to me and and it's smooth in all gear ranges,especially when downshifting and excelerating out of a turn.
Theres no muck showing up on the dip stick and there wasn't any in the oil filter can when I changed the filter w/the oil change.
We'll see (knock on wood).
Dave

Got the new thermostat in friday and installed it today. I also recieved a later model 4 PSI radiator cap and rigged up an over flow tank to catch any coolant should it run too hot.
I took two long cruises and the temps climbed up to 180 pretty fast and stayed there. It would run alittle hotter when idleing than cruising but the needle never past the "0" of 180.
I pulled the valve cover after the 1st cruise and there was alittle condensation but it was probably what was still in the engine from before. I adjusted the valves and went on another cruise. There was no condenstaion around the oil fill after the 2nd time.
I'm going to monitor to see if this clears it.
Funny, I didn't set out to make the engine better for the ecology but the pcv valve and overflow tank are definitely "green" friendly

Since I'm working the night shift tonight exercising a backup generator, I thought about this old thread and thought I'd update it after monitoring these engine mods through a cold cold winter.
Since the last update theres only been a handful of days where the temps avg'ed in the high 50's and on those rare days the engine had no condensation nor milky white buildup in the valve cover, none.
On the vast majority of days I ran it with the temps below 55, in some cases way below 30, I'd get the buildup in the valve cover.
55 degrees seems to be the magic number.
Closing up the top 3 vents in the valve cover and only venting through the oil filler cap actually made it worse.... So they are open.
Visable blowby is just about gone. Seems the more I run it the better it gets.

The coolant level in the tank varied but I never had to add any additional coolant to the radiator. Had I not had an overflow tank I would have had to have added coolant.
The radiator sprang a leak on top of the tank which I patched w/J B Weld and it's holding good and strong.

With all the mods I've done to try to allieveate the condensation I can say they didn't help it one bit but, I believe the PCV is helping the engine to breath/vent much better than the stock draft tube and the coolant overflow system has saved me $$$'s by not having to add coolant so I'm glad I added them anyways.

Come warmer temps I expect my condensation problem will go away also, until next winter
Dave



My area is very humid all yr long.

On that coolant thing Dave. I haven't been following this, don't
know if you've been having a problem with leaking coolant or
what. But, cold the coolant will be just barely above the
header and tubes. When warmed up it will fill the tank. A
mistake that a lot of people make it thinking that the radiator
should be topped off when it's cold. As you've discovered, if
you do that you better have an over flow tank or you will be
mopping up the driveway.
I've been running my '50, 216 level that way for nearly ten
years now and have never had an over heating problem even on hot
days sitting at idle in slow traffic for an hour at a crack.

Nothing wrong with over filling and catching what it puked out
as long as your not going over the pressure limit of the
cooling system, (7lbs max.)
Denny Graham
Sandwich, IL

Good info Denny.
I didn't think I had a coolant leak problem but in troubleshooting this condensation problem I wanted to eliminate the coolant system from the equation.
I found out pretty quickly that the radiator liked the coolant level to be just barely above the bottom of the tank.
When I 1st got it running I had completely filled it and within a couple trips I noticed the level was lower and there was coolant in the cross member below the radiator.

So in troubleshooting I decided to top it off to the very top again when I added the overflow tank to catch what it spit out and monitor. I'm happy to report that I didn't/don't have a coolant leak problem as I can easily refill the radiator back up to the tip top by just emptying the overflow tank back into it.

Oddly the tank does vary in the level of coolant in it at any given time. I have 3 marks on it. The original low mark where the engine originally filled it, a middle mark where it will get to after a long cruise and a high mark where it rarely gets but does on those warmer days.

Usually it will draw back down to the low mark but not immediately and sometimes not over night. I haven't quite figured out any definite SOP for how often the tanks level changes but the engine stays at a steady 180 and has never overheated on me (knock on wood).

I'd like to add one of those optional OEM tanks and/or one of those aftermarket stainless steel ones one of these days but my rigged up tanks works fine for now.

Temps today reached in the mid 60's and I took it out for a little cruise and get some new/used skins on the front, no condensation to report.
I'm going to chalk my cold weather condensation situation up as SOP :D
Dave