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Build up on radiator cap.

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Jul 21, 2019, 9:03 AM

Post #1 of 3 (243 views)
Build up on radiator cap. Sign In

I bought a 2004 v6 Mustang and noticed that the coolant was a dark orange color so I changed it to the green coolant. At the time, the radiator cap had a lot of thick gooey brown build up on it so I wiped it off. Now it’s about 3 weeks later and the build up on the radiator cap is back. What could it be caused from? Thanks.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Jul 21, 2019, 9:20 AM

Post #2 of 3 (230 views)
Re: Build up on radiator cap. Sign In

The goey cap thing? If you are mixing up coolant types plus if vapor ( even small amounts) get in can do that? Not totally sure total reason. I actually think some is rust from cheap junk "freeze plugs" also called core plugs can't see from outside. It's from lack of rust protection at some point in its life. You'd really have to flush this out should be drain bolts of some sort low on the sides of the block. It's built up some crud you can't get out with much if those are still in icky stuff drops low in water jackets whatever the cause.
You have to know pressure caps work, both ways means holds pressure to listed pressure and vents properly too. That crud can interfere with the vent back or suck back from recovery bottles the tube or how done may have lost being sealed and has to. Air out, liquid back.
Unless you have to remove an engine clean the bottle out too out of the car you can get there. Do use only what it called for, for type of antifreeze mixed as suggested as well without wild mistakes too strong or too weak,


Hammer Time
Ultimate Carjunky / Moderator
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Jul 21, 2019, 9:39 AM

Post #3 of 3 (227 views)
Re: Build up on radiator cap. Sign In

Are you sure that was red coolant and not just rusty water?

Either way, that sediment is throughout the inside of the block and other components and needs to be flushed thoroughly.

Green coolant is pretty much a thing of the past. Most all newer cars require specialized coolant, most of them are silicate free and considered a 5 year coolant as opposed to green coolant which is only a 2 year coolant.

Your car actually takes a special yellow coolant.

Motorcraft Premium Gold Engine Coolant VC-7-A (in Oregon VC-7-B) or equivalent (yellow-color)

Ford Specification .................... WSS-M97B51-A1


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