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Discussion Starter #1
Well my trusty 2002 Focus wagon's thermostat housing finally got its crack and has been leaking coolant all week. Luckily i detected this on Monday and have been pouring a few oz. antifreeze in every day. Its some little nearly invisible crack on the topside of the housing that sends a tiny stream down onto the lower hoses and goes all over the stuff below and even the transmission.

So I listened to all your really nice postings (thanks again Fanatics), and went to O'Reillys and bought the complete Dorman thermostat housing kit .

Now my question is that O ring on the housing. Am I supposed to lubricate it (the clerk at O'Reillys said use vaseline), or should I use something beefier like Permatex 2B form-a-gasket?

I really, really hate having to do thermostat work twice and have already had my share of housings that just want to leak.

I'd like to tackle this tomorrow so any suggestions from you-all would be listened to.

thanks,
-lytt Alpharetta, GA
 

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DTC P0606
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Personally, I wouldn't lubricate it with anything. It's not like it's a seal around a rotating part. The only reason I would see to use a small blob of grease or vaseline would be to hold it in place and prevent the O-ring from slipping out of position while another part is fitted. It's not really an issue with the T-stat housing; it's held in a groove, iirc.
 

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Agree wit cha

BC ZX3...right on. Put it on dry, make sure the block or head is clean. Then clean it again before installation of housing. And by the way, might as well buy another new thermostat housing now as it will need another new one in a couple years! JMO.
 

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Discussion Starter #4
OK, sounds like nothing is really needed. Kind of surprising--but I have never been very good with gaskets on cars and I'd like to break my string of failures. Glad I dialedf\ up the Fanatics before I went crazy with this problem--there are a bunch of threads on this same problem! The leak is so small and insidious that I doubt I would have guessed the housing itself.

I'll let you all know how this job turns out.
 

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BACON?
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You can't go wrong with a little Vaseline. I use it on o-rings all the time, mostly when they need to slide in to a hole. It helps everything slid together easily. I would apply a light coating to the entire gasket before installation. it will help the gasket spread when its being crushed by the outer piece. I did use a little on mine when replaced. no issues after 5k. It might not be needed but does not hurt.
 

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I've used anything that'll hold it in it's "groove" in different applications.

Dab 'O Vaseline SURE won't hurt... the big issue is the dang thing getting out of position during installation (See "Space Shuttle")

Gask-A-Cinch, a liquid gasket sealer similar to contact cement, was the preferred method to keep intake sealing O-rings in place when installing manifolds on motorcycles - with a bit in the groove, they'd stay in place through multiple installations.

Black RTV was the "glue" (sealant) of choice for keeping rubber valve cover gaskets where THEY belong - and you could pull the cover & reinstall for tune-ups as required without fighting the dang thing into position.

Inspection caps to oil filled areas (valve covers, gear boxes, rear ends) that used O-rings - a bit of "axle grease" was handy to keep 'em in the groove, and it didn't hurt anything...

(I wouldn't worry about "petroleum based", in most cases "petroleum" is what you are sealing, so the appropriate material was used for the O-rings. (neoprene for example)

Luck!

P.S. - As long as an O-ring stays where it belongs, and doesn't get "pinched", it'll do it's job!
 

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I got tired of chipping gaskets off and haven't used permatex in decades. I use a few dabs of chassis grease or wheel bearing grease on those rare cork or metal gaskets and silicone grease on all rubber seals. Holds them in place and not hard to disassemble. If it's anywhere in the combustion path make sure it's O2 sensor safe; some compounds will ruin a sensor.
 

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I just bought new housing and thermostat. The connector that has self tapping screws was another 60$!! So l definitely am reusing the old one since it looks fine. Should I clean the connector surface where it contacts the thermostat o-ring with anything special? I used wet paper towel.
 

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You lube o-rings since they have to usually slide a certain distance to get to the end point they stay in. You do not lube stat seal since it can allow the seal to simply slide out of place, you definitely do NOT want that there. The lube also allows the seal to squeeze flatter and thinner by sideslip instead of being positively pinched by friction against the housing sides. I used to see warranty seals brought back that the user lubed up liberally, seal had slipped around one side to be too much there but nothing to seal on other side. They blamed the seal, I blamed the lube, when installed dry second time they did not come back again.

When you install the housing bolts only tighten them until you feel the solid hit then stop, overtightening too much is what cracks all the housings here onsite, you cannot use the feel of a solid metal part there for your torque. It will seem like not tight enough but last forever.
 

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I see the metal sleeves for each bolt, they meant to prevent cracking? I read on another thread the housing bolts were 15ft-lbs (think they got that from all data). Then I saw somewhere else, prob focaljet, it was 16ft-lbs.

Should I just torque them with my little clicker to 180 in-lbs (15ft-lbs)?

What about where the connector meets the thermostat o-ring, it looks kind of discolored from but the surface is flat. What do you guys clean all these plastic engine parts with?
 

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just tighten it evenly by hand. you would be amazed at how easy it is to strip bolt holes in the head when trying to use a torque wrench with a "little clicker"
 

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You cannot fine tune it enough. 15 pounds is in parts breaking territory, and that tool is garbage for this job..

Look here, you either get this or you don't...............

Old school torque numbers are for joints that have to squeeze a gasket or other that had resistance, you needed the extra force to crush a gasket out flat to seal properly. On modern engines the simple silicone rubber seals they use can be crushed to seal with hand pressure alone, that's how they get away with using weak plastic parts to seal now. Once you pull the new plastic part up till it hits solid, the seal is crushed as much as it is EVER going to get, any additional force you put in there is only cracking your plastic part. I only pull up bolts until I feel them hit solid, the force will increase then, you can feel it unless you are a butcher. Then tighten a wee nudge more just to guarantee that it is solid and then stop. Any urge you have to go further is only screwing yourself, look how many of these parts routinely break, many, MANY times..............I have 3 zetecs, each has now had ORIGINAL stat housings off more than once and I never go any more torque than what I just said, in fact I never have used a torque wrench at all there. So far not one leak or cracked part.

Actually that's a lie about the leak part, one stat front cover started leaking a small drop or two, I pulled cover to find the rubber o-ring maybe not as thick as it should be and/or cover pulling in at bolt hole corners to release pressure in between the bolt holes. The rubber o-ring clearly not squeezing quite enough. I bought a $1 washer .040" thick from hardware store of proper OD and ID and added to the rubber o-ring to make thicker and again tightened like I said above, except this time didn't even hit solid. Since I increased the squeeze by .040" I used a .010" feeler gauge and pulled all bolts up till the gauge was just tight between front cover and housing, meaning I ended up with .030" more overall squeeze. I used a bit of silicone to seal between the washer and front cover since gasket does not seal there any more, also used it on bolts since the cover not pulled tight, didn't want bolts backing out. Got that? ZERO torque there.....car has now been like that a long time and not even a drop leaking anymore. Thinking some of the cheaper rubber o-rings given out as parts not quite as thick as they should be, who's surprised at that?

Here it is............a torque wrench even if gold-plated is totally useless when you are only squeezing something so soft it will never register as a resistance on the wrench. Maybe a low scale inch pound wrench will work and down low around 50-100 meaning well beyond the ability of a conventional over the counter bigger wrench. Of course, I have one but force there so low it's not needed. You have one right there, or the hit solid, which provides correct seal crush as soon as you are there.
 

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On plastic parts of this type, sleeves provide a bit of a "crush limit". When new, the plastic will be JUST a little thicker than the length of the sleeve. When the bolt is tightened on a part like this, the plastic gets squeezed just a little B4 the bolt bottoms on the sleeve. Any more torque at this point will start to distort the part as the sleeve gets worn/crushed often leading to early failure of the part.

The 15 ft./lb. spec on this size fastener is a maximum value that's easy to exceed. Tightening 'till "snug" is recommended by folks who've experienced the issues arising from over-tightening fasteners in this type of application. Running it in until you feel that sudden increase in resistance to turning as it snugs up against the sleeve, plus a SLIGHT additional twist to "lock" it there (compensates for how it backs off ever so slightly as the wrench tension is released) - That's a good description of using "feel" to get it just right.

Problems arise sometimes when one continues to tighten past this point to achieve a torque spec.. On these small parts the variables involved can result in exceeding the yield strength of the pieces involved, and occasionally the slow turn of the wrench just keeps going as the materials yield - parts can even break completely without achieving the torque spec. desired. That's an extreme case, and also one that everyone who turns a wrench long enough will see eventually.

Torque specs. were invented to avoid this problem. A generic spec. on a small fastener is a well known exception where the spec. is best used as a guide for those with no idea how much force to apply, as opposed to a target that needs to be achieved on each fastener installed.

NOT trying to "Preach" here, this is just one of those odd areas where experience CAN trump rather generic written instructions. It's also a difficult lesson to pass on, much as we'd like to, since it's a "motor skill" that can only be learned by actual experience - and even with practice one can be "fooled" in a particular situation.

That tiny "clicker" can be handy for quick assembly work if it's accuracy is good, as long as 'feel" is kept in mind. If you ever get the chance, using a beam type on small bolts can reveal quite a bit as you see the values all through the tightening sequence. Reaching a value near spec., then seeing little increase with a lot of turning - that's a graphic demonstration of having reached the yield limit of the parts involved.

take care & good luck!
 

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Thanks for your wisdom. I just put the old connector piece on the new housing and the self tapping screws reused. When they're snug there's a gap you can see between the two pieces since you don't want to crush the thermostat o-ring to hard, right?

How bad should the block be pitted around the water outlet to warrant RTV usage? Can I clean it off with Emory cloth?
 

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Cleaning off the corrosion with emery cloth would be a good idea, and I like the idea of smearing a bit of black RTV over the pitting when assembling it. Much better than ending up with a wavy surface from trying to buff out all the pitting.

Sounds like a plan!

Cheers
 

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I got the thermostat connector screws snug but there's still like 1/8th of an inch gap? Will I have to retighten later when stat oring heats up?
 
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