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Discussion Starter #1 (Edited)
Zetec t-stat housing alternatives

Not the typical zetec thermostat housing leak in my opinion although that may be the cause. I noticed my lower radiator hose is about to blow so I changed it. The coolant was leaking before from over by the thermostat housing. When I replace the lower radiator hose the valve cover started leaking but the coolant leak stopped from over by the thermostat housing. So I replaced my valve cover and gasket nownmy coolant leak is back.
But my coolant only leaks when the car is cooling off. Still on that side of the motor but why would it do that. Seems to be linking up the backside to my knowledge the thermostat has never been changed same for the housing.
Any ideas ? Maybe I should check the torque on the bolts for the thermostat housing?
 

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Moved to General Tech Chat.
 

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Discussion Starter #3
OK leak stopped. Loosened my rad cap a little. Wonder if there is too much pressure. Its not boiling over or leaking up there at all either. Gonna try the cap. Makes sense if there is too much pressure and it pushes through the crappy ford seal.
 

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"only leaks when the car is cooling off" ...typical as max pressure is reached just after engine shut off.

Loosening the cap may stop the leak, but it won't solve the issue. The reason loosening the cap makes the leak go away is because that lowers the pressure.

You may have to clean everything off so that you can spot the leak. Put the cap back down and warm the engine to operating temp. Shut off the engine and start looking for the source.
 

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Discussion Starter #5
I'm curious as to if a faulty radiator cap building too much pressure is what's causing a lot of people that have to put on repeated housings and seals
 

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Faulty radiator caps 99.99999% of the time LOWER pressure, not increase it. Barking up invisible tree there, you have no evidence the cap is over pressure at all.

You gotta leak, fix it. Stat housings can leak ten different ways. The leak can come and go at least at first. DON'T tighten bolts more, odds are the stat being old will crack, done properly the bolts are not tight anyway.

Lots of parts because the stat housing was designed by an idiot. Plastic, cheap thin wall to support the o-ring, the o-ring itself is not robust. Plastic used has a definite lifespan after which it begins to crack all over the place. Then to make it worse they re-design to even crappier plastic and change up the front cover bolt pattern to leak much easier too. Or, re-designed by even bigger idiot. The front cover bolt pattern was done by a five year old. Instead of extra bolt they notch the plastic deeper to fail at that point really quick, even brand new ones won't seal sometimes.
 

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The problem isn't the design of the tstat housing the problem is the material they used. I could probably cast up one of these housings in my backyard but it would need significant machining and drilling. No way to make it cheaply with an aluminum casting that's why they went to plastic.

There's a couple aluminum replacements out there:

http://www.bostig.com/bostig-billet-thermostat-housing-for-zetec-focus/

http://www.topspeedparts.com/Aluminum-Thermostat-Housing_p_665.html

The Dorman part is cheap, it's a complete assembly with a new thermostat and seals, and it will last at least another 75K miles assuming it doesn't leak when you bolt it on.

Most people give up and find another battle to fight on this one.
 

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Discussion Starter #10
The problem isn't the design of the tstat housing the problem is the material they used. I could probably cast up one of these housings in my backyard but it would need significant machining and drilling. No way to make it cheaply with an aluminum casting that's why they went to plastic. I work in manufacturing and know what it's costs to mold one up.

There's a couple aluminum replacements out there:

http://www.bostig.com/bostig-billet-thermostat-housing-for-zetec-focus/

http://www.topspeedparts.com/Aluminum-Thermostat-Housing_p_665.html

The Dorman part is cheap, it's a complete assembly with a new thermostat and seals, and it will last at least another 75K miles assuming it doesn't leak when you bolt it on.


Most people give up and find another battle to fight on this one.
There different grades of plastic to be used as well. Ford didn't make this in plastic to be cheap per say they made it in plastic to get more service money. Sure they last until the warranty is done but they bank on post warranty service money as well. The SOHC motors are a fine example of purposely using defective design to generate dollars in service department.

I have also heard of the contour housing working and it is metal isnt it? I can deal with using a plug in the ect sensor hole on it. Anyone had luck with them? What year range contour works?

Not trying to be a pain but I would prefer a better chance of a more long term fix. Seems to be a lot of "it was good for 3-6 month and started leaking again" post with the plastic ones.

May drop 199 on a new one that you linked but not ready to yet.

Thnaks for the info!
 

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Contour was a different design plastic one, had the stat cover holes spaced like the one from CFM you posted (not oddly spaced).

CFM version should be an improvement if yours is bad.
 

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There are 2 tricks with the plastic housing first is the head that you bolt them to must be smooth, some of these get pitted or corroded and then there is not a smooth mating surface to seal to. Some have had success with a light film of sealant on the surface. The other trick is not over tightening the mounting bolts/screws. Put them hand tight.
 

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Discussion Starter #13
There are 2 tricks with the plastic housing first is the head that you bolt them to must be smooth, some of these get pitted or corroded and then there is not a smooth mating surface to seal to. Some have had success with a light film of sealant on the surface. The other trick is not over tightening the mounting bolts/screws. Put them hand tight.
Hand tight with fingers? I have a torque wrench and figured spec would do...not right?
 

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The lip simply degrades to crack apart, the choice of 'improved' plastic Ford went to and the extremely thin cross section used there. The Contour one besides having a much better bolt pattern is made of bakelite plastic, a lot stiffer than the ABS used on these, the ABS breaks down over time from heat and cracks literally everywhere. You can pull off material on old ones with your fingernail, it just crumbles. I've seen as many as five cracks in one before. The later Focus front stat cover also has a dent molded into it that flexes because of the oddball bolt pattern, I've seen brand new off the shelf covers leak at that stress notch, the cover warps when you tighten it up, you can see it. The o-ring crush drops and your leak. In short Ford took a fairly reliable part and re-engineered it to fail much sooner by design, ain't no other way to look at it. They know the cars last too long now and are actively engineering them to make more part sales in the future. You can see it in fifty other places on the cars.

You do NOT overtighten these, death to do so. Strive to kiss as evenly as possible all three bolts and then handtight and not a heavy hand at all. Overtighten and the heat will crack them really quick. You get one shot at the seal, if it leaks start over, there is absolutely no re-tightening the bolts tighter to seal better, it gets worse when you do that. These seal by the housing ring holding the seal in place, not by gasket crush like oldschool stuff did. Two totally different sealing processes there.
 

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Discussion Starter #20
Use '98-'00 Contour not SVT, they last forever but don't overtighten the plug(s), plastic part remember? Use a bit of sealant on them and fine. You'll need different bolts for the front cover and a o-ring for stat of course.

http://www.rockauto.com/catalog/moreinfo.php?pk=379402&cc=1354373

http://www.rockauto.com/catalog/moreinfo.php?pk=379425&cc=1354373
Thanks for all that information. I can source bolts for it at my local ace hardware. They have a great stainless metric selection. Nice part is they are allen head so over tightening would be difficult. So these two are the housing and tstat outlet you suggest right? As far as the o-ring goes. since it is a contour housing and outlet wouldn't the oring be a contour one like this?
Fel-Pro Contour Thermostat Seal

I also suppose I would need a contour thermostat for the housing right?
Contour 195 Thermostat

Thanks for the help by the way. There is so much cross information in past threads it's hard to see whats found to work better now vs old threads. I'll get a plug for the hole at ace hardware too.
I am pretty good at turning wrenchs but only want to do this once for a while if possible so hence the questions.

Would you suggest using the OEM seal that comes with the housing or an aftermarket one for the head to housing seal?
 
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