Slight leak from inlet manifold

[Thin Lizzy]

Hi All,

I took my car for a nice 200 mile drive the other day. When I parked it up, I noticed a smell of oil. I lifted the hood and noticed a slight weep from the inlet manifold gasket, at the back of the engine. It's weeping over the transmission. The engine is a 302.

Could you please tell me if I need to tighten up the bolts or do I need to remove the intake manifold, put new gaskets on and reseal it?

Thanks for any help you can give.

 

[MotoArts]

I would give the bolts a snug job first, but chances are, if the gaskets are original (cork) they won't seal up. The end "China wall" strip is probably the offender.

I've also had luck (on a beater 5.0 powered car) with degreasing the affected area very well (as in 100% clean) and smearing black RTV around the leak. Certainly not pretty, but it got the job done.

The oil isn't under any pressure in that area, just sprayed around and like you called it, weepy.

If it doesn't work, you aren't out much time or money and it needed resealed anyways.

 

[Thin Lizzy]

The engine was rebuilt a few years ago and there's white sealant around the gasket. I'll tighten up the bolts and see what happens.

Thanks for your help.

 

[Thin Lizzy]

Here's a pic of the leak. Do you think it's a leak from the inlet manifold or the transmission?

And the engine:

 

[jpaz]

That looks like a manifold leak to me.

 

[Elizabeth73]

I just did a rebuild on my engine about a month ago and used "Permatex Ultra Copper Gasket Maker" to seal all of my gaskets. It is the only stuff I use. Put it on real light with a decent Felpro gasket and you will most likely not encounter another leak.

Before my tranny went, I ran the car everyday after the rebuild and I experienced no leaks at all. I am sure there are other great products you could use but thats just my experience.

 

[Thin Lizzy]

Thanks for the info. Do you think tightening the bolts will fix this, or do I need to take the manifold off, put new gaskets on and reseal it?

 

[Elizabeth73]

You could try cleaning the area really well with degreaser and car cleaner and then use something like the Permatex to seal it. Just make sure you really push the sealer in to get it in amy crack and crevice you can. This is probably more of a temporary fix though.

Not sure what others would say, but if it were me I would just get some good gaskets and sealer and just do the whole intake so you won't have to worry later on. It probably sucks to hear that but better being sure you sealed it good then to constantly worry and risk an even larger leak.

 

[72HCODE]

that is a common area to get a leak..

do you know if the builder used the cork gaskets there, clean up the mess with some brake cleaner and if you see cork then you need to pull the manifold out. the cork gaskets should never be used.

now if you clean it up and see RTV then the manifold should still come off as something went wrong during the install.

clean it all up, pull the manifold, clean the surfaces get new gaskets and then you need hi temp RTV, you have to lay a 1/4" bead across the center section.

what you do is dab RTV into the 4 corners then put the exhuast gasket on and line them up. then lay a 1/4" thick bead from the corners ontop of the gasket across the lifter valley ridge. let it sit for about 5 minutes then drop the manifold on top and torque to spec 2 times.

watch this video it is for a chevy however the install goes the same way with the RTV and gaskets.



as a note you may not need to pull the distributor out to get the manifold on and off, depends on what distributor you have on the engine.

one other thing, do you have a PCV on the motor or just breathers, a PCV can help stop leaks like this.

 

[Thin Lizzy]

Thanks very much for the information. It used to have a PCV valve on the right side rocker cover. I replaced it with a breather. I wonder if this may have caused it.

 

[72HCODE]

you will want to think about putting the PCV back on.

the PCV creates a negative crank case pressure inside the block, this helps hold the oil in and reduce leaks.

it also reduces oil varnish, keeps the oil cleaner longer, and removes moisture from the block.

you could go to a slightly thicker oil also to reduce leaking but you want to try and fix the leak.

in this case a PCV might not make a change if the leak is bad.

 

[Jeff73Mach1]

PCV is worth having.

I would recommend you pull the intake manifold and fix it with new gaskets and a better installation than was done previously.

Cleaning and RTVing the rear might work, but that is a hard place to work effectively and not get crud dropped into the valley.

It is a bit harder on a 302 than on a cleveland as the coolant in the heads and intake tend to get into the oil when you pull it apart. With the cooling system open and drained, you can use a shop vac on the manifold before pulling the intake and it will reduce the spillage a great deal, but if your cooling system is dirty or rusty, you'll dislodge crap and may cause other problems.

 

[Thin Lizzy]

Sounds like another job for the garage. My spanner skills are next to zero .

I'll tell the garage your information. Thanks again for this .

 

[wwhite72]

302 have wet intake, as mentioned above. Clevelands are dry and have big problems with intake air leaks. If yer 302 has an intake leak you will want to drain/replace with new coolant, change oil, reinstall intake with new gaskets and tips mentioned above. I dont recall 289/302/351W's having a lot of intake leaks problems. Are you seeing evidence of a leak other than the offensive oil film on the back of the engine? Any significant change in performance? When my Cleveland developed an intake leak it caused a significant change in performance and exhaust was double the normal readings

 

[Thin Lizzy]

There are no other leaks I can see and the performance seems fine.

 

[wwhite72]

your initial post mentioned smell of oil and the visual evidence of a leak out the back. My experience of intake leaks produced a leak of air into the engine. I dont recall seeing any oil leaking out of the engine. Since you see no evidence of performance change, and you dont mention oil in coolant, or any change in exhaust...chances are you do not have an intake manifold leak. A thorough cleaning of the back of your engine where the buildup is showing may help finding the source going forward. best of luck.

 

[Thin Lizzy]

I've just checked the coolant and there's no oil in it. I've had a good look and can't where else it could be coming from. All the pipes around it are dry.

 

[Jeff73Mach1]

I'd start by cleaning the area thoroughly and just run the car and drive it a bit. Fresh leaks are easier to identify.

I understand everyone isn't comfortable with a wrench in their hand and grease under their finger nails. If you ever want to learn more, you have to jump in and give it a try sometimes. This is not the simplest project, but it isn't very difficult and requires only a few tools to do right if you wanted to try.

 

[mjlan]

If I were you, I would clean the s*&t out of that area and then add the PCV valve back into the system as this may stop the leak.

As has been mentioned, the PCV creates negative pressure in the crankcase, and by removing it, you now have positive pressure in the crankcase which is looking to find it's way out to the lower pressure atmosphere. This positive pressure is due to combustion gasses passing by the rings and pressurizing the crankcase with cylinder pressure. So, not only do you have vaporized oil and moisture floating around under the valve covers and intake, you have vaporized unburned fuel as well. I'm surprised that after removing the PCV you didn't notice a drastic increase in oil and gas smells around the car.

Add the PCV back into the system with a proper filter on the incoming air (either through the air cleaner base or a valve cover) and see if the leak slows down...