Howdy, I just got a '78 308 driver. My mysterious location in my profile is just because of some land in Ireland I own that barely eclipses the amount I own here in the southeast part of the US. I have a rainy day fund but can't afford to pay for professional help for everything. Most serious issue with the car is is an oil leak. I don't mind drips but this is of the puddle variety. I am not brimming with mechanical aptitude but have the desire and learned a lot here already. And so I have an ambitious first project. Upon inspection I thought the oil pan, each oil pan stud, the shift shaft seal, plus various higher areas were leaking. Then, I cleaned everything underneath real good, drove for an hour or so, and inspected. Wow. No leak at the shift shaft. No leak at the pan. Maybe 6/20 pan studs leaking. Few drips around the gearbox and drain plug. Left rear leak seems mostly from up above. By far the worst leaks seem to be at the front motor mounts, especially the front right motor mount. Doesn't seem to be from the top there. Weeping at the distributors and cam seals but timing belts dry. So, I removed the right front motor mount -- a stretch for me but I had researched it here a lot before starting. I started late today, but that's where I am now. Confirmed leak there is not coming from up at the cam seals. My plan is to remove the motor mount studs and coat with Permatex #2. I do not plan to use any sealant on what I refer to as the "backing plate" that sits between the case and the bracket for the mount. I welcome any additional advice or cautions for the uninitiated . The questions I have are concerning the dip stick tube and the oil return tube. I am seeing what appears to be significant oil deposits around them. Do they have seals that I should be replacing while I'm here? Thanks, Seamus
I don't believe that your engine mount stud holes go all the way to into the sump. I know they don't on the 4V engines. However, I'm not quite so sure about the 2V trannys. You'll find out when you pull the studs tho. There's a copper crush washer under the dipstick, but nothing under the oil return tube. I've never encountered either of them leaking unless someone pulled the dipstick tube & didn't reinstall the Cu crush washer. In a pinch, thoroughly degrease the threads & give them a thin coating of Loctite PST, or use teflon pipe tape to seal the threads. However, my bet is that it's your front bank cam seals &/or cam covers leaking. The oil from either of these will drip off of the boss protruding just below the cam covers on the RH front corner of the engine. Usually you'll just see a drop hanging from the boss, with nothing on the block below it, but oil on the motor mount, around the dipstick studs, & sucked into the back of the alternator.
So, what's with all these posts (especially in old F-chat) about leaking motor mount studs? After my test run, I could literally watch the oil leak from the mount's mounting plate. Wipe it clean, and within seconds it would be leaking again. When I pulled the mount's backing plate, the cavity behind it was full of oil -- maybe a 1/2 cup or so. I pulled one stud (lower left). Seems solid right behind the stud. I don't want to pull them and coat them for nothing. I hear what you are saying about the cam seals and covers, but I'm still having a hard time actually seeing much oil coming down from up there. And I really don't see how it could be coming down from up there and accumulating in huge quantities behind the motor mount. What's going on here? Seem like 1) Pouring down from up top and accumulating behind the mount. 2) Oil somehow can make way to mount studs. 3) Dipstick conneciton leaking and getting in behind mount. Seamus
studs do not go through to sump unless someone messed up previously. Should be able to use a stud remover to take them out, though they can be very tight from my own experience. Most likely source is a leak from dip stick tube, but that should be obvious if pooling. No seal per say just a copper ring if my memory is working, I used a high temp silicone seal on mine when I reinstalled it after a rebuild. Only other sources should be cam cover leak dripping down, or cam seal leak, but it would have to be fairly bad for that much oil.
I've seen the space behind the motor mounts full of oil, water, or a mixture of both. Most likely it accumulated over time. It's conceivable that that oil is left over from a previous service that sealed up the actual leak! Water is worse to have there because it corrodes the nuts onto the studs. Now when I pull mounts, I drill a 3/16" drain hole, or file a V-notch to stop the accumulation. When I've got both rear mounts off, I clamp the motor side of the 2 spacers together & drill a 1/4" hole down thru the clamped seam. This leaves a half circle drain hole when the spacers are back in place. My recommendatin would be to not pull the studs at this time. If you break one or ruin the threads, you'll have to pull the engine. I'd clean everything up, drill drain holes as I described, and then see if the drip reappears. I do remember reading those old Fchat stud oil leak threads when they were first posted. That's why I've been taking a good look when I've had the sump cover off. So far I haven't seen an engine with any openings to the studs. I just went back & reread the old posts. One reported that the oil ended up coming from the spacer as I described above. However another did report that some motor mount stud holes had been drilled just deep enough to have a small hole into the sump. Oil splashing around in the sump could wick out around the studs. I've never seen this 2nd case. Another possible source of the leak is the seam where the sump/tranny casting joins the block.
Thanks for the replies. Verell, I'll take your recommendation. As I removed the one stud I kept thinking, "What if?". It came off fine, but given I found no evidence of it going into the sump I'm not going to temp fate with the other studs. The drain hole is a great idea. The dipstick tube has no copper crush washer. The tube itself is tapered at the end. The way the nut attaches it to the sump is what I would describe as similar to some of the plumbing connections in my house. I don't really see how Loctite PST helps here -- that nut just presses the tube down. The hose just to the right of the dipstick and in the middle -- how much oil runs through it? If so, I might have found my culprit. It was not only loose, but upon further examination I found it cracked for a good inch or two going up. Thanks, Seamus
Okay, traced that middle hose up. Enters a small cylinder/filter, then terminates under the air box. Seems like its purpose is ventilation? Maybe someone can verify? Seamus
Do you have your Owner's Manual? It has several great systems diagrams, oil being one of them...anyone have it digitized to post?
Hey, thanks! I appreciate the encouragement, especially after removing one motor mount for nothing. Well, actually, not for nothing . Verell's idea of drilling the backing plates is a great idea. At least then I think if it leaks it will do so on demand and not for 30 minutes after I park it in my garage. Seamus
The smaller hose that ends at the air plenum is a breather tube, which ventillates the crankcase through an oil collection canister. Oil does get up into those lines, so if one is leaking or cracked, it could be a problem. Here's the Oil Flow diagram for the engine. For some reason, I couldn't copy the image out of the pdf document, so I screen captured it. With a large oil leak, there is a clean washed-down area where the oil is escaping, surrounded by a dirty area. My engine has a leak just to the right of the differential (from behind the engine) between the engine block and the gearbox. We didn't find it until the engine was dropped out. I was loosing about 2 quarts of oil on a 600 mile drive. One of the nuts attaching the gearbox to the bottom of the engine block is missing where the stud has snapped off behind the differential. Oil was collecting on the flat just behind the differential. It's a major effort to repair, since the engine has to come out of the subframe, then the clutch and associated housings have to come off before you can unbolt the gearbox to replace the main seal. It stinks, but after reading the burned-up Ferrari threads I decided to get it fixed. I have a fuel leak as well, somewhere in the filler neck which also has to get fixed immediately, and the coolant hoses are getting replaced as well. Some of the sections look original, ie. 25 years old. I hope your oil leak is not where mine is. Thor www.JavelinArt.com Image Unavailable, Please Login
The crush washer is between the bottom fitting of the dipstick 'pipe union' joint & the block. Odds are that fitting has never been off of the car & the washer is sealing just fine. I have seen leaks in the pipe union style joint you're describing, usually when the ball fitting on the dipstick tube has gotten dinged somehow. The hose you're describing goes up to what's called a 'vapor recovery' canister. It's part of the crankcase ventilation system shown in the drawing. It's purpose is to collect & condense crankcase oil vapor & then let it drain down the hose into the crankcase. The hose isn't under any pressure, and doesn't have a significant amount of oil flow. However, if it's cracked, you'll get oil in that area, and the oil will flow along the casting ridge below the fitting to the motor mounts.
It's back together now. I went for a good ride. I checked a few hours after I returned. No Exxon Valdez. I am pleased so far. I have a hard time believing the breather hose leak was responsible for all the oil I was seeing. But, at least that's one leak fixed. The bigger ones are still out there I'm sure. Took me awhile to come up with a replacement breather hose. In the end it occurred to me a custom motorcycle builder would have bulk stainless steel braided oil line in stock and sure enough they did. Part of the solution was drilling the mount and backing plate so oil and water don't accumulate there. I'm sure I have leaks higher up but for now things are better. Have a pint on me. Seamus
the above image doesn't really show the hose being talked about, so below is a better pic for injected cars. It's #11. On the 308, the hose makes a 90 degree bend at the crankcase end. Age, oil, and probably heat harden the hose and it cracks at the bend. Worse, the crack will create a low resistance airflow path to the air box, so oil can get sucked up into the intake through the vapor canister, and some of it will drain back out the crack when the engine is shut off. If you remove the air filter and find oil in the bottom of the airbox, this hose is a good place to check....and yeah, oil is probably in the rest of the intake and plenum. Any rubber hose (e.g. low pressure fuel hose) can be used to replace the line...it's far enough away from the header to not melt. The 328 US spec cars and maybe some others use a banjo T fitting at #4 due to an oil temp switch getting attached there, so there is no bend in the hose to crack even though the hose is hardened also. Image Unavailable, Please Login
