New to M35, getting started, where am I leaking?

[clob mcstrunk]

Picked up a 1972 M35a2 from a member on here. After a headache of a time dealing with the freight hauler...and then the small issue of him getting stuck coming down the driveway, she landed in the shop.

Since I got it home I have:
-Tagged and insured
-Replaced all 6 wheel cylinders, adjusted to .020/.010 clearance on all pads, bled, went through >$40 of brake fluid, bled some more and got the stoppers dialed in
-Replaced axle seals, little cork thingys, and axle shaft seals
-Replaced all rubber hoses
-Replaced all zerks, put more grease through my grease gun then in its entire life to date
-Replaced parking brake cable (likely going to replace the shoes at some point in not distant future)
-Removed/pressure washed/scrubbed interior, rebuilt driver's seat linkages, replaced damper
-Removed, blasted, repainted: grill, mirror brackets, exhaust guard
-All hardware that has been touched by a wrench has been replaced with grade8 nuts/bolts, for vanity of course
-Racked up the most expensive single fill-up in my driving history
-Dismounted 4 extra wheels/tires that I got with the sale (thanks @sgms18.) Wheels have been cleaned and prepped for the 395s Im getting, just need to figure out tubes and flaps, local truck service center seems to have no clue about the flaps.
-Naturally replaced the shifter knob with a pineapple

Up until yesterday I was only bold enough to take it around the 6 mile loop around the neighborhood, having never driven one I felt it probably in everyone's best interest to pop my cherry on some backroads. Then yesterday, after being bored and frustrated at work (being essential and all

) I decided a longer shakedown was in order. Spent about an hour on everything from residential and highway, 4th and 5th really do feel like where the truck is happiest and other than being a 48-year old government-built truck, feels quite solid.

The few times I've driven prior to yesterday I've noticed a fair bit of fresh oil on the starter and dripping below. I thought it may be dripping from the slobber tube, as there was a bit of residue at the bottom of it, but I could never isolate that is the source. Well yesterday when I stopped to be the jerk that took up 4 spots at the grocery store, I came out and saw a lot of oil coating the front diff, passenger side leafs, underside of the battery cabinet, etc. etc. A LOT of oil. Getting home I checked the level (one min after shut down as spec'd) and was down almost a quarter. Crawling underneath I cant pinpoint the source, but the passenger rear corner of the oil pan looks suspicious. There is still some oil on top of the starter, but nothing higher, nothing on the block/turbo/head/etc.

I've already put into a shopping cart for rear main seal, clutch pack, etc., thinking that with all I've read this may be the source, but something is nagging at me that it might be elsewhere. I dont feel any slippage in the clutch, which as I have read is likely from the oil spraying.

Any suggestions? I know (and have read) there are fortyeleven threads about the rear main but none seem to corroborate with what I'm seeing. But then again this is my first rodeo so maybe I'm wrong or looking at the wrong thing.

Thanks!


Tl;dr - Love the truck, cant figure out oil leak, kthx

 

[Slate]

Pictures help alot.

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[simp5782]

You use 14.00R20 tubes/flaps for 395s

 

[montaillou]

Racked up the most expensive single fill-up in my driving history

Sounds like you need to put on a second fuel tank!

 

[cattlerepairman]

The oil supply and oil return lines for the turbo sit on the passenger side near the starter. Return line has a fabric covered piece of high temp hose to connect the metal line to the block....I'd be suspieious of that one. Other than these, it may be the oil pan itself or its seal leaking in this corner. Pics, please!

 

[cattlerepairman]

Here are the pics from the manual re turbo lines:






Difficult to see but a head gasket oil leak at the rear of the block could also have oil running down the back of the block and then over to one side and down onto the starter. Something to look for.

 

[glcaines]

Be mindful that oil leaking while driving can be blown around by air movement and can mislead you on where the oil is actually coming from. I would recommend thoroughly cleaning the engine, differential and anywhere else that has oil on it. Start the engine and let it run for a long time while you look for the oil leak. Do not drive the truck. If you don't see the leak, pull the throttle some to increase the engine speed / oil pressure and again look for the leak. You will find the leak if you are persistent.

 

[Slate]

Here are the pics from the manual re turbo lines:

View attachment 796483

View attachment 796484


Difficult to see but a head gasket oil leak at the rear of the block could also have oil running down the back of the block and then over to one side and down onto the starter. Something to look for.

Mine did this. The line got a crack in it and dripped on the springs and axle. Didn't leak unless it was running of course. Then I fixed it and when I did I tore the little #10 gasket and it was leaking from there. All good now with a new hose and gasket.

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[Menaces Nemesis]

Be mindful that oil leaking while driving can be blown around by air movement and can mislead you on where the oil is actually coming from. I would recommend thoroughly cleaning the engine, differential and anywhere else that has oil on it. Start the engine and let it run for a long time while you look for the oil leak. Do not drive the truck. If you don't see the leak, pull the throttle some to increase the engine speed / oil pressure and again look for the leak. You will find the leak if you are persistent.

That's exactly what you need to do... Degrease and rinse it thoroughly and let it dry completely. Everything should look dull and ashy. If it still looks shiny after it's dried, you probably didn't get it degreased well enough. Start it up and scrutinize it early and often w/flashlight in hand. If you see it weeping from somewhere, shut it down and snug-up every-dang fastener even remotely in the vacinity of the suspected leak. It's amazing how many things can be "fixed" by simply snugging things up a bit.

 

[clob mcstrunk]

Turbo in/out oil passages are clean and dry, block is dry, passenger side/rear head area clean. Slobber tube is normal amount, not the source


Underside of bellhousing, oil is only on pass side, up to the centerline point on the pan


This is my guess on the source, oil pan gasket ...?


Front side of starter looking back


I really appreciate all the help. I have not degreased everything off yet, i keep the ol girl in the hangar and didnt want to fire it up to move it outside before I documented the condition as-is. I will get it moved outside and cleaned up this afternoon, let it dry, and then let it run in place until it shows the leak source.

 

[fleetmech]

looks list mist blowing back from the vent tube all over the starter anyway. Should there be an extension tube to take that vent down lower? Maybe that rubber extension tube fell off?

 

[gringeltaube]

.... Should there be an extension tube to take that vent down lower? Maybe that rubber extension tube fell off?

That's what I thought when seeing the picture. He is missing the so-called "road draft tube" - which should extend down below the front axle.

 

[Aussie Bloke]

G'day everyone,......


I agree, its just missing the extension tube to go down below the axle.

However, I am still concerned about the volume of oil used.




Aussie.

 

[fleetmech]

G'day everyone,......


I agree, its just missing the extension tube to go down below the axle.

However, I am still concerned about the volume of oil used.




Aussie.

Yeah, I have to go look at my dipstick to get a handle on how much 'one quarter' really represents, but definitely too much for a days driving. We might be seeing two different oil patches, the haze on the starter from the tube, as well as another leak in the same area.

OP, you might consider adding some leak detection dye to the oil before you do your clean-and -run cycle. Even if you don't have a uv detection light those dyes are usually pretty bright and will still be helpful in ID-ing the source of the leak. Dyes and lights are available through many major part stores, and probably amazon too, though I haven't looked.

Also, in your third picture, right where your yellow mark is, right by the starter, is that hole a missing pan bolt? If so, thats not helping!

 

[gringeltaube]

is that hole a missing pan bolt?

No. From what I can see, bolts are all there.



Maybe they are just loose?

 

[clob mcstrunk]

All oil pan bolts are accounted for.

I cleaned the underside, let it run until reached operating temp - no leak.

Increased throttle and held it for 5 min - no leak.

Drove it 4 miles, including up to 50+ mph, got out and checked, with engine still running - everything is soaked with oil. Underside of starter is the heaviest coated, but can’t see the source.

Does it make sense that the leak is only happening while at speed? How much pressure could there be in the oil pan?

Clutch still feels as it should, no slipping.

 

[Slate]

Turbo oil return line.

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[M37M35]

Turbo in/out oil passages are clean and dry, block is dry, passenger side/rear head area clean. Slobber tube is normal amount, not the source

Your slobber tube should have a piece of hose about 2' long attached to it that ends below the front axle to direct any oil vapor away from the engine. Have you added a hose to it yet?

How much pressure could there be in the oil pan?

Little to none, unless a dirt-dobber has made a nest in the slobber tube and plugged it up. I'd verify the slobber tube is clear, add a length of hose to it, and clean things up and try again.

 

[frank8003]

All oil pan bolts are accounted for.

I cleaned the underside, let it run until reached operating temp - no leak.

Increased throttle and held it for 5 min - no leak.

Drove it 4 miles, including up to 50+ mph, got out and checked, with engine still running - everything is soaked with oil. Underside of starter is the heaviest coated, but can’t see the source.

Does it make sense that the leak is only happening while at speed? How much pressure could there be in the oil pan?

Clutch still feels as it should, no slipping.

not supposed to be any pressure in the oil pan.........................
Atop the engine is a breather of the valve covers, gets plugged, in the TM's, easy to clean, can't hurt being cleaned.

 

[clob mcstrunk]

To update, I've got the oil pan gasket, new oil filters, new crush washers, etc. sitting on the workbench. Drained the oil, pulled the pan, and found two scary things.

Drained over 7 gallons of oil. This is after pissing at least a few pints out (if not more) during the last two drives.


Found this in the pan:


It is solid, not a tube. When doing an initial inspection, I cant see where it might have broken off from. Can someone please tell me what it is and more importantly that isnt something that is going to make me want to cry?

The gasket that I removed was the single-piece style and did have a spot that looks like it could have been letting oil past, though not as big as I would have thought. The new gasket from Memphis Equipment is the mult-piece style, and one of the end sections is a different material than the other three. The thickness of all pieces is the same; should I be concerned? I've used RVT on plenty of applications in the past and have found conflicting reports of using it here. What about if RVT + paper gasket? Thoughts?