Starting this post because this has been an ongoing problem for years....
Most Auto Parts places sell you this gasket for the thermostat housing. This full flange gasket is almost useless when you need the ring type. The circled area is usual point of failure because there is barely any seal there.
The Ring type seems to no longer exist (discontinued?). But there must be a good alternative.
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⚠️ Warning: There are 2 T-stat housing for Fiero L4. Maybe more but Actually seen and have two types.
Simple Three hole Gasket above are for old type w/ the flange is totally flat where meets engine. This type has thin sheet metal flange w/ edges rolled 90° "up." This Gasket Must Not be used w/ T-stat came w/ a "rubber" seal in Groove in the Flange.
Later "update" version has thick flat stamp steel flange and use the "rubber" seal. I don't know exactly what year first came w/ it but If it is in 84--- Very Likely the whole engine was replace under warranty/recall.
I don't think RA or any others have a seal for updated T-stat pipe. Example: FEL-PRO 35342 "O-ring" O-Ring Thickness (in) 0.1 O-Ring Outside Diameter (in) 1.725 O-Ring Inside Diameter (in) 1.5249 And maybe too thin even if others are correct.
I had to make a gasket. Made of thick cork (⅛/0.125 inch I think. not digging it out to post now.) Permatex made for custom caskets to fill up most of the gap and coat w/ RTV and Wait a few of Days to cure completely before fill the system. This before "glueing" both sides.
Yes, I know don't use RTV w/ nearly all gaskets. Problem is 2 fold... The Thick cork barely or don't compress and trying to fill big gap w/ RTV alone won't take 15+ PSI Coolant very long either. Between the 2 and allowing RTV to completely cure is been 6+ Years and still seals.
RTV takes Hours to Days to cure. Curing Is Not Drying. Dry RTV w/o time to cure has cause huge problems to people using them.
[This message has been edited by fierosound (edited 09-18-2020).]
Dug thru old pic's... (2014 when fix mine w/ DIY "gasket.")
Here are both types w/ old "rubber" on update one...
Another angle of the update one...
If you have the old style one, many have bent flanges. Likely related to long hose pulling on it, worse if you have crap dog bone and/or motor/trans mounts. If you bend it flat, only warps again for same reasons and likely easier as bending weaken it. Above old type was warped then flatten and didn't install for this reason.
Might find gm 10038440 ACDelco 15-80794 but is whole thing and cost ~ 30 - 40 often more. Many claim has X old part but out of stock on page or at checkout.
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Originally posted by fierosound: "Old style" looks like it has a groove for the O-ring seal - the part listed in P22 Book. Felpro just decided to make a flat flange gasket.
No. The "goove" in the old style is just extra metal for a seem where tube joints to the base flange. Or seem for part holding inner tube. Don't have pic of other side area and can't find the part now. "Paper" gasket from FelPro et al seals the whole flange area to try to eveny load on the part and bolts. Same setup used by many OEMs not just GM.
P22 and OEM often don't match what in installed at the factory. Most people only have crappy pirate scanned copy P22 often sold as CD years ago. That 84-86 Duke Head shows # 61 T-stat Housing w/ new style PN 10038440 retain by 2 bolts and #28 "Sealant, Silicone RTV" w/o PN likely is the new "o-ring." If GM have older version of P22 likely had 61 old T-stat pipe # and 28 w/ a gasket #. Or GM may not bother w/ a gasket like did w/ many Duke valve cover gaskets. 87-88 head list is about the same but no "extra" number from a gasket #. So I guess 87 started the new style.
Many RWD and FWD dukes old type flange w/o a problem most times. But If they have crap dog bone and/or engine/trans mounts then can have same problem. Example: People sold me the Fiero also had FWD Olds w/ same engine had broken dog bone mount and wreck PS Pump and more. Told them to donate or junk it because can't fix damage themselves or spend a lot more money.
[This message has been edited by theogre (edited 09-18-2020).]
Found this part number for Pontiac/Olds Duke engines in Stant's vintage catalog - seal available at Rock Auto. The thermostat housing I have came off an Olds Ciera Duke (SD4 in Indy didn't have one). At just over 1/8" thick, I think this is what we need.
[This message has been edited by fierosound (edited 09-25-2020).]
Is hard to tell from 1 iffy picture but at least doesn't cost allot. RA said had "glue" on 1 side to stay put installing it so I thought maybe flat ring? Is it even close to fit?
I think the glue on one side refers to paper type gaskets, because this rubber seal didn't have anything. So you'd need to use a gasket goo to hold it in place. Not happy with the fit but doable I guess.
It looks like Mahle had part number RV6 as a replacement for "original equipment uses RTV" - discontinued of course.
Felpro lists a ring gasket for Duke EZ Fill thermostat housing, but no dimensional data.
Couldn't find one anywhere in Canada - seems to happen a lot with Felpro. So ordered from RockAuto. Gasket is cheap, but RockAuto shipping to Canada is $10. (Stant one was $7 off Amazon.ca)
[This message has been edited by fierosound (edited 10-01-2020).]
Felpro 35342 is identical to GM PN 3049485 O-ring pictured above. The question now is what the hell does it fit anyway? A 3rd style of thermostat housing?
Because if it doesn’t fit either Fiero thermostat housing though the part is listed ??
I’d just as soon use the larger Stant 25282 O-ring and use a dab of contact cement to hold it in place. The only other alternative appears to be to put an O-ring like bead of RTV in the groove and let it fully cure before installing.
[This message has been edited by fierosound (edited 10-13-2020).]
bottom ring is likely too big to compress right. Over Compressing rubber can squeeze out, break or both. More so w/ gap isn't complete close like here.
Could do same as "my" top post above. Cheap and works. Or Find "better then cork" and do similar. Cork composite material isn't crap that many think. Most just have no clue how to use it right. Could find 2 or 3 small rings that nest to fit. Small as size of "rubber" like 1/8" to 3/16" to compress good. 2 or 3 different total sizes to nest w/o bothering each other.
Could search and buy new T'stat tube hopefully should come w/ the gasket. Cost $30 to $50 each. For many this is a better option because tube often have "Rust" eating thru the sides, at top making hard to seal the cap or both. One of my "spares" has holes thru the side, One use has minor top rust.
Saw this in another thread for original T-stat housing with rolled edge. May work better than FelPro 35062 gasket in that application.
Originally posted by AsaBergman:
I had this issue on the 84. Previous owner overtightened and bent the flange. I used gasket "Felpro 35562 T". It is a hard plastic gasket with a rubber o ring. Install dry, no sealant. The bolt holes have to be elongated with a file to fit. Never leaked a drop after two years and multiple removals. No overheating issues. If the flange on the housing is corroded you must clean it good.