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Old 09-02-2020, 12:37 PM   #1
paulbrgr9999
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350 with more leaks than you can imagine

My 350 has developed a little puddle of oil on the intake manifold. It's the first bolt on the passenger side. The bolt is tight. But it appears to me that the oil is leaking up through the bolt. So a little puddle of oil appears. See pic. I also have a leak at the front of the oil pan. Or so it appears. 1970 Chevy C20 350 with 4 barrel carb automatic transmission.
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Last edited by LockDoc; 09-02-2020 at 12:47 PM. Reason: Political overtones
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Old 09-02-2020, 02:16 PM   #2
geezer#99
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Re: 350 with more leaks than you can imagine

That’s normal if you don’t put sealant on them. Some of the bolts are open into the lifter valley and crankcase pressure can push oil up the threads.
I use sealant like this.

https://www.ebay.com/itm/Permatex-Bo...-/163277419986

Front of pan leak can be timing cover seal or pan gasket.

Some leaks are caused by too much crankcase pressure.
A non working or missing pcv system can cause this.
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Old 09-02-2020, 02:25 PM   #3
paulbrgr9999
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Re: 350 with more leaks than you can imagine

Thank you for the reply. Do you put the sealant on all the threads of the bolt? Or just the top threads?
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Old 09-02-2020, 02:45 PM   #4
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Re: 350 with more leaks than you can imagine

Wipe a bunch on the bottom threads and the threads will be coated as you screw the bolt in.
You got pics of the top of your motor so we can see your set up.
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Old 09-02-2020, 02:52 PM   #5
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Re: 350 with more leaks than you can imagine

Okay thank you for the reply.

On the PCV valve that you mentioned. How would I know if it's defective? I must admit I have heard of a PCV valve but I had no idea what it did until I watched a YouTube video a few minutes ago. I hope I didn't ruin any gaskets in the engine by not servicing the valve. It's only $1.69 at O'Reilly's.
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Old 09-02-2020, 02:56 PM   #6
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Re: 350 with more leaks than you can imagine

Whether correct or not I just pull them out of the cover and rattle them. Make noise they’re good.
Again.
Got pics?
We might see something amiss.
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Old 09-02-2020, 03:07 PM   #7
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Re: 350 with more leaks than you can imagine

I gave it a good shake I don't hear anything rattling.
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Old 09-02-2020, 04:32 PM   #8
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Re: 350 with more leaks than you can imagine

That’s cause it ain’t a stock one.
It’s like this.

https://www.summitracing.com/parts/sum-440308

Who knows if it’s working or not.

Stock one might work better.
Where’s pic of pass side valve cover?
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Old 09-02-2020, 04:35 PM   #9
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Re: 350 with more leaks than you can imagine

That's a newer type of valve, it may not make any noise.

Pull one intake bolt at a time. The threaded shank of the bolt should be 1-1/4 inch long. Thoroughly clean the bolt. Coating all the threads on the bolt will not hurt anything. I use ultra black RTV by permatex. You can squirt a little carb cleaner down the bolt hole to rinse some of the oil back into the engine. The bolt holes are al lopen into the crank case of the engine. A little carb cleaner will not hurt anything.
If your intake is aluminum, you will need to re-check the bolts for tightness after the engine has cooled completely down from running. May need to do this more than once, especially with the middle 4 bolts (they are next to the exhaust crossover).
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Old 09-02-2020, 05:16 PM   #10
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Re: 350 with more leaks than you can imagine

Carefull with that one bolt at a time method.
Some bolts open up into the coolant passages.
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Old 09-03-2020, 09:08 AM   #11
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Re: 350 with more leaks than you can imagine

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Originally Posted by geezer#99 View Post
Carefull with that one bolt at a time method.
Some bolts open up into the coolant passages.
Good call.
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Old 09-03-2020, 12:47 PM   #12
paulbrgr9999
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Re: 350 with more leaks than you can imagine

Here's pictures of the passenger side. Which I guess would be the clean air side of the PCV valve system. Looks like there's a filter inside that hose that plugs into the valve cover.
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Old 09-03-2020, 12:51 PM   #13
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Re: 350 with more leaks than you can imagine

By the amount of oil around that grommet I bet it's as hard as a rock. They're cheap to replace.
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Old 09-03-2020, 12:58 PM   #14
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Re: 350 with more leaks than you can imagine

It does take quite a bit of force to get that metal end of the hose back into the valve cover. Should I replace that screen that you can see inside the end of the hose? And is the amount of oil in that area another symptom of a bad PCV system?
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Old 09-03-2020, 01:10 PM   #15
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Re: 350 with more leaks than you can imagine

Get a stock pcv. That shiny one likely isn’t working well.
Leave that screen alone. It’s actually a spark arrestor. Works like a restrictor if you have a backfire in the carb.
It’s a stock piece.
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Old 09-03-2020, 07:46 PM   #16
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Re: 350 with more leaks than you can imagine

So my next question is: are there any oil additives that you would recommend that could stop the leaks. Or is all that stuff just snake oil.

Thanks for the information and responses.
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Old 09-03-2020, 08:29 PM   #17
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Re: 350 with more leaks than you can imagine

Yup!
Snake oil.
You need to fix the leaks with new gaskets.
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Old 09-03-2020, 09:41 PM   #18
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Re: 350 with more leaks than you can imagine

I had an engine in a truck I've bought leak like a sieve, no crankcase ventilation, old style valve covers. I put the correct valve covers on with PCV and breather on other side, tightened up all bolts, and no leaks... except vacuum on intake due to leaking valley gasket. Sounded like a tea kettle . Pulled that, resealed, good to go.
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Old 09-04-2020, 07:04 AM   #19
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Re: 350 with more leaks than you can imagine

Quote:
Originally Posted by paulbrgr9999 View Post
So my next question is: are there any oil additives that you would recommend that could stop the leaks. Or is all that stuff just snake oil.

Thanks for the information and responses.
SNAKE OIL!
Leaks come from worn/cracked gaskets. Replace them
Your issue is from capillary action, that has already been explained. It’s a common oversight on a rebuild, and an easy fix.
Thickening the fluid does nothing to fix the cause.
Actually, “Leak Stoppers” only temporarily cover up issues and create more problems.
Ever put “Bars Leak“ in your cooling system? It’ll gum up your T-stat faster than you can get the cap back on.
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Old 11-20-2020, 11:20 AM   #20
paulbrgr9999
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Re: 350 with more leaks than you can imagine

Just a quick update. I put the RTV on the bolt and tightened it down and there's no longer a little puddle of oil forming in that area of the intake manifold. Thank you for all the responses.
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Old 11-20-2020, 08:53 PM   #21
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Re: 350 with more leaks than you can imagine

Boog mentioned that the grommet is probably hard as a rock. A new grommet will seal better and make it easier to take that hose off/on.

The simple tool below is used for checking the PCV System. With the engine idling and the oil fill cap removed, this is placed on the fill hole for a go/no go indication.

You can also just place the palm of your hand over the fill hole or a strip of paper. There should be a slight vacuum felt.

If there is smoke coming out the fill hole, the PCV is not working or there is way too much blow-by for the PCV system to handle
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Old 11-20-2020, 10:30 PM   #22
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Re: 350 with more leaks than you can imagine

When you get a new PCV Valve check the amount of vacuum on the hose. I have seen them plug up.
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Old 11-21-2020, 07:09 PM   #23
weim55
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Re: 350 with more leaks than you can imagine

Quote:
Originally Posted by RichardJ View Post
Boog mentioned that the grommet is probably hard as a rock. A new grommet will seal better and make it easier to take that hose off/on.

The simple tool below is used for checking the PCV System. With the engine idling and the oil fill cap removed, this is placed on the fill hole for a go/no go indication.

You can also just place the palm of your hand over the fill hole or a strip of paper. There should be a slight vacuum felt.

If there is smoke coming out the fill hole, the PCV is not working or there is way too much blow-by for the PCV system to handle

Wow, i’ve never seen a tool like that before?! Where in the world did you acquire that, looks like something from the 70s! What you say for testing the system and having a slight vacuum in the crank case is correct. The blow by pressure can be the cause of oil leaks at various points on the engine as well. Typical on a high mileage worn out motor.

Steve weim55 Colorado
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Old 11-21-2020, 10:58 PM   #24
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Re: 350 with more leaks than you can imagine

We had those when I worked as a mechanic in the '60s. I usually use my hand to check for suction or pressure these days but (for example), Toyotas will exhibit pressure with the oil filler cap off. The newer stuff works differently from these old trucks, for sure.
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Old 11-22-2020, 03:55 AM   #25
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Re: 350 with more leaks than you can imagine

Quote:
Originally Posted by weim55 View Post
Wow, i’ve never seen a tool like that before?! Where in the world did you acquire that, looks like something from the 70s! What you say for testing the system and having a slight vacuum in the crank case is correct. The blow by pressure can be the cause of oil leaks at various points on the engine as well. Typical on a high mileage worn out motor.

Steve weim55 Colorado
I was wondering the same thing. I would love to own something like that. I would store it next to my dwell meter.

Seriously cool though. I haven't seen something like that either.
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