Electrolysis, pitting on intake manifold - Vintage Mustang Forums
 
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post #1 of 6 (permalink) Old 02-08-2019, 01:18 AM Thread Starter
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Electrolysis, pitting on intake manifold

Hello everyone, I am taking the intake manifold of my 1969 convertible to address some leaking issues, and there is a lot of pitting and corrosion of the aluminum on the surfaces around the water galleys, is this normal? The intake is an Edelbrock performance dual plane and looks pretty new, it appears to be something added in the last 10 years/ 5000 miles.

I think it was leaking into the intake ports because I was getting a ton of condensation out of the tailpipes and it looks like the corrosion made it all the way between the ports on one corner. I pulled the heads and the head gaskets did not appear to have been leaking.

I am trying not to spend a lot of money on this project right now so I am planning to just seal it up as well as I can and put it back together with new gaskets. The PO put about a whole tube of RTV on the intake manifold, but it was still leaking oil like crazy because the cork piece across the front got pushed back into the lifter area before he torqued the intake down.

All in all the engine seems to run quite well aside from a water pump bearing and the leaking oil and maybe water (might not have actually been leaking, might just be corroded.)

So yeah, does anybody know what can exacerbate or retard the advancement of corrosion around the cooant ports?

Thanks

-Layne
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post #2 of 6 (permalink) Old 02-08-2019, 06:33 AM
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You got the corrosion because of the dissimilar metals in the engine and an acidic condition of the coolant mixture. This is why you should change the antifreeze on a regular basis at least every 3 to 4 years.

Clean up the mating surfaces and use a smear of RTV on both sides of the intake manifold gasket around all the intake ports and the water passages, including the rear passages that are blocked off by the intake manifold. The cork seals can be disposed of and use a thick bead of RTV to make your own seal. Let the RTV skin over before setting the intake manifold in place. Torque the manifold to spec. There are several videos on YouTube showing the RTV procedure.

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post #3 of 6 (permalink) Old 02-08-2019, 09:48 AM
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For the record, condensation or water out the tailpipes is a normal by-product of combustion. If it smells like antifreeze, that's another issue.

I would true the two gasket faces of the intake with a large flat file. This will show you any high or low spots that need attention. The bead of RTV on the end walls is a good way to do it, but the cork works fine if you use an adhesive to glue the cork to the block. Edelbrock recommends their o-ring style intake gaskets for aluminum intakes.

https://www.edelbrock.com/intake-man...ords-7220.html

As long as the corrosion is not into the area where the seal bears, you should be fine. Be sure to use a 50/50 mix of antifreeze to prevent any further corrosion.

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post #4 of 6 (permalink) Old 02-08-2019, 12:06 PM Thread Starter
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I have had condensation come out of SBF motors before, but never of this quantity... that said, I don't think I will worry about it, just make sure that when I put it back together the gaskets are all sealed well and do a good 50/50 mix of antifreeze with good RO water so that the PH is not too high or low. perhaps they just left the same coolant in the system for the whole time.

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post #5 of 6 (permalink) Old 02-08-2019, 12:54 PM
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I had my 60's vintage Edelbrock intake powder coated inside & out. The powder coating shop I used does a lot of work for Offshore racers. He says they all powder coat their manifolds inside & outside because of the harsh salt water environment they run in. Just FYI.
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post #6 of 6 (permalink) Old 02-08-2019, 02:02 PM
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One thing I've done is move over to a "phosphate" style of coolant which is supposed to really help with this exact kind of issue on older cars. Also it happens to be specified for newer Asian vehicles. The kind I like is Nissan blue color PHOAT. Newer Nissan is green. Toyota specifies basically the exact same stuff but for some reason pink. Or orange. Though the mixtures are essentially the same you don't want to mix Toyota and Nissan because it makes a horrible color. But they excel at long term corrosion protection in cars that are rarely driven. Nissan claims their newer green stuff to be good for up to ten years in a stored vehicle situation. The blue is almost as good (plus it's blue!)

Unlike Dex-Cool any of those mix fine with any residual old-school green antifreeze that might still be in the car. So you don't have to be completely anal about flushing it out.

Though you are supposed to mix coolant with deionized or distilled water, sometimes you have to use what you have. If you have "hard" tap water and may be using it at some point you would be better served by an HOAT coolant like specified for European built cars. VW, Jaguar, etc.
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