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Discussion Starter · #1 ·
I am finally getting around to fixing the pinhole leak from my thermostat housing gasket.

The new gasket I bought from CSK has a tiny fourth hole. You know, three holes for the bolts and then whatever that other hole is for is tiny.

What is the chamber in the housing that the fourth hole feeds for?

If you look at some of the gaskets on rock auto the fourth hole is always at least as big as the bolt holes and sometimes significantly larger.

Should I punch out the tiny fourth hole to at least the size of the bolt holes? Maybe larger? Inquiring minds want to know.

Edit: I guess technically its the fifth hole if you count the water outlet hole.
 

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I know the hole is to allow water to flow past a closed thermostat, not only so the heater will work sooner in freezing weather, but to make the engine get uniformly warmer without bringing in cold coolant flow from the radiator. i would make the hole in the gasket the same size as the hole in the thermostat housing.
I would be glad to learn what is inside the extra passages in the thermostat housing, and what happens if it malfunctions. (Every part will eventually fail, and i keep my cars a long time).
 

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If it's the hole I think you're talking about, it's for a bypass in the housing. Inside the smaller passage of the thermostat housing, there's a plastic valve that is designed to melt in the event the thermostat gets stuck closed. You can usually hear it rattling when you shake the housing.

Casey
 

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Discussion Starter · #4 ·
Word.

I just left it alone and I got the leak fixed. No more gassing myself with sizzling coolant at stoplights! Woot!

Inexplicably enough I found a few aluminum shavings in my coolant (I had to relocate the hole in the housing and the head because of an broken extractor I couldn't drill out). I had everything plugged up while drilling but I guess some of shavings got past my barriers.

These are some pretty tiny shavings. Is this the sort of thing that will cause me problems (i.e. clogged heater core) or is this the kind of thing that just sits in the bottom of the radiator and block and doesn't move through the system?
 

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Discussion Starter · #5 ·
Also, how much rust would be acceptable in an 02 with 90000 miles on it? The coolant was still green when I drained it but there was a film of brown stuff at the bottom of the clear container I used to catch it (I assume this is rust).

I am sure no rust would be preferable but.... anyhow, is this the sort of thing that once started eats up the block and I am screwed or will the rusting slow down (or hopefully end) with the right mix of coolant in there?
 

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Enough rust from the inside of the water jacket in the block to coat the bottom of a jar - would be normal after 90,000 miles. Also after 30,000 miles for that matter. Once the inside of the block has rusted somewhat, the corrosion of the cast iron slows down. You dont need to worry about it. Probably the best thing to use is the pre-mixed antifreeze that is 50% water, 50% ethylene glycol, and to drain it out and replace with new about each 2 or 3 years. I like to catch rainwater to mix with the etylene glycol, since our tap water tends to have lots of alkali chemicals in it.


I think small bits all wind up in the bottom of the radiator, or in a low corner of the water jacket in the block.
 

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did you flush out the radiator with water really good before you refilled it?
 

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Discussion Starter · #8 ·
Sadly no, I didn't drain the radiator all the way out. Just about three quarts or so.

I honestly can't figure out how the shavings got in there. After I unplugged the water outlet hole I probed around with my finger and didn't really find much at all, I pulled out anything I found as best I could. What came out of the draincock looked like way more than I pulled out.
 

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could be the radiator fins breaking apart.
 
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