1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

81 12a coolant leak

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Old 04-18-20, 05:08 PM
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81 12a coolant leak

Hey all, so this all started when I pulled my headers off to get my exhaust welded up, as I started to pull them off coolant started leaking from it and after I got it off I’d say about a cup total had leaked out. I have a Bridgeport 12a Weber 48 Ida there are freeze plugs on the intake so I start pulling the intake off and a ton of coolant leaks out I had read it could be due to the o-rings on the intake being bad and it’s leaking through into the housings? Also I don’t drive it a ton i had been having some hard start issues but I thought this was due to flooding so I’d de-flood the car, and it would smoke like the write ups suggest so I didn’t think anything of it but anyway I drove it to our new apartment it I let warm up smoked heavily, started driving and i got about a half mile and it stopped completely temp looked good it sounded good nothing really seemed out of the ordinary so I am writing this post I unfortunately need to move my car putting it at my cousins until I can buy a house, but will I need a rebuild? No problem with doing that. Or will I be okay to just replace intake gasket and o rings just to drive it there ? Also took some pics let me know what you guys think,





thanks!

Last edited by AlexA69; 04-18-20 at 05:56 PM.
Old 04-18-20, 06:56 PM
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You can do a pressure test at the rad to test the internal water seals and intake freeze plug you added.
Old 04-18-20, 07:02 PM
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Originally Posted by KansasCityREPU
You can do a pressure test at the rad to test the internal water seals and intake freeze plug you added.
okay great I will check that out freeze plugs were added to manifold by the last owner, but I’ll do that pressure test and see where that leads me thanks!
Old 04-19-20, 07:23 AM
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Can you post pics of the manifold? The IDA manifolds I am thinking of won't have any coolant circuit and will just be a flat aluminum flange. That flange would cover freeze plugs (and OEM o-rings) as backups.

Typically the freeze plugs are installed into the housings, like in the right hand side of image #2 you posted.

Then can do a leak check... if your seals are gone then you don't want the engine sitting filled with water/coolant.
Old 04-19-20, 09:44 AM
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Yeah, what Tommy said ^^^. The freeze plugs go into the engine (rotor housings) where the o-rings are. I have a RB IDA intake and it doesnt have any coolant passages to plug. I dont think the other brands do either.

The coolant port in your picture is not plugged, so any time you remove the intake manifold coolant will come out of those coolant ports. I always drain the coolant from the motor before I pull the intake manifold, for less mess.

The coolant in your exhaust port picture looks like it is running down from the water ports above, which makes sense if you had coolant in the engine. Also the intake manifold is just called as manifold, even if aftermarket. The name "header" is just used for aftermarket exhaust... a hand made tubular exhaust manifold.

If I go pull my intake manifold off, coolant will pour down all over that side of the engine, just like your pics. Drain some coolant out first, and hopefully there isn't really anything wrong with your motor. Use new o-rings when you put it back together and install freeze plugs if you dont want this wet mess everytime you remove the intake manifold.

Last edited by Maxwedge; 04-19-20 at 09:56 AM.
Old 04-19-20, 01:07 PM
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Originally Posted by tommyeflight89
Can you post pics of the manifold? The IDA manifolds I am thinking of won't have any coolant circuit and will just be a flat aluminum flange. That flange would cover freeze plugs (and OEM o-rings) as backups.

Typically the freeze plugs are installed into the housings, like in the right hand side of image #2 you posted.

Then can do a leak check... if your seals are gone then you don't want the engine sitting filled with water/coolant.
Originally Posted by Maxwedge
Yeah, what Tommy said ^^^. The freeze plugs go into the engine (rotor housings) where the o-rings are. I have a RB IDA intake and it doesnt have any coolant passages to plug. I dont think the other brands do either.

The coolant port in your picture is not plugged, so any time you remove the intake manifold coolant will come out of those coolant ports. I always drain the coolant from the motor before I pull the intake manifold, for less mess.

The coolant in your exhaust port picture looks like it is running down from the water ports above, which makes sense if you had coolant in the engine. Also the intake manifold is just called as manifold, even if aftermarket. The name "header" is just used for aftermarket exhaust... a hand made tubular exhaust manifold.

If I go pull my intake manifold off, coolant will pour down all over that side of the engine, just like your pics. Drain some coolant out first, and hopefully there isn't really anything wrong with your motor. Use new o-rings when you put it back together and install freeze plugs if you dont want this wet mess everytime you remove the intake manifold.
here is a pic of the manifold I had assumed that these were what had been plugged just judging from how it looked or ... now that I am looking at it I think it may be whatever the previous owner used for the o rings and it’s just the marks left I never really looked hard at the manifold, so with that should I put freeze plugs or just replace o rings and gaskets for the manifold?


Last edited by AlexA69; 04-19-20 at 01:10 PM.
Old 04-19-20, 05:21 PM
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Ya those circular marks you see are leftover from the o-rings squishing up againts the aluminum.. The downdraft (non OEM) manifolds do not have coolant circuits.

I would install freeze plugs (20MM) into your housings and a new set of o-rings. Might as well do the freeze plugs now so you aren't dealing with coolant again like Maxwedge mentions.

Mazda part number for new o rings is: 8527-13-113 qty2

And probably a good idea to replace the intake gasket also.

And don't forget to refill coolant and bleed the system!
Old 04-19-20, 05:58 PM
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Originally Posted by tommyeflight89
Ya those circular marks you see are leftover from the o-rings squishing up againts the aluminum.. The downdraft (non OEM) manifolds do not have coolant circuits.

I would install freeze plugs (20MM) into your housings and a new set of o-rings. Might as well do the freeze plugs now so you aren't dealing with coolant again like Maxwedge mentions.

Mazda part number for new o rings is: 8527-13-113 qty2

And probably a good idea to replace the intake gasket also.

And don't forget to refill coolant and bleed the system!
okay great I actually ordered new orings and gasket from racing beat before I even took it off so I’ll get those plugs and I’ll replace the coolant I already drained everything so I’ll get everything replaced thank you guys!!
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