T-Stat Hosing - Aluminium or Cast Iron?

Hypoid said:

Gee, I thought they were all pot metal! :gee:

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LOL, me too! But I'd avoid cast iron for the rust factor and that aluminum is a little more flexible. The t-stat housing for 90+ 4.0 is not possible to install the stat backwards. My 88 housing has a bigger "bulb" and can be installed backwards.

The key is, spring towards the head and if the stat has a jiggle valve, it should be at the top. Some guys with the closed system will drill a 1/8" hole at 6 and 12 to reduce bubbles forming or getting "stuck" behind the stat. Anyway, installing the stat can be tricky as the stat itself can slip out "just a hair"

I would not depend on the stick-um on the gasket to keep it in place. I've been the victim of impatience too often (two cracked housings). So, I make sure everything is bone dry, then just put a few tiny dabs of RTV on the stat, seat it good and walk away. Come back a half hour later and stab the housing. If you have to crank the bolt on...something's wrong.

I think that may be where my problem is, that the T-stat may have slipped a little. The gasket LOOKs like it is even all around, but maybe not. I have not tried to seat the T-stat using RTV, gasket glue, or some other adhesive. That will be my next step tomorrow.

Idk. Bolts are only speced to like 13 or 15 ftlbs. Could you have over tightened? Did you snug them evenly?

desertred said:

I think that may be where my problem is, that the T-stat may have slipped a little. The gasket LOOKs like it is even all around, but maybe not. I have not tried to seat the T-stat using RTV, gasket glue, or some other adhesive. That will be my next step tomorrow.

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That was my first guess, nevermind how I came to that conclusion. :dunce:

Before you reassemble everything, check the Thermostat Housing for flatness: Put some medium grit sand paper on a flat surface and rub the mating surface of the housing on the sand paper. Look at the housing, if there are shiny spots, and not shiny spots, you bent the housing. If the entire sealing surface shows contact with the sand paper, you dodged a bullet. Nevermind how I learned this procedure. :dunce:

Waynerd said:

Idk. Bolts are only speced to like 13 or 15 ftlbs. Could you have over tightened? Did you snug them evenly?

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Yep, on both accounts. Snugged them down evenly and tightened to the FSM spec of 13 ft-lbs.

@Hypoid - The housing is new due to concerns that my old one may have warped a bit causing the initial leak. Hopefully, it wasn't bad right out of the box (but its been known to happen). I have also been making sure that the mating surfaces have been very clean. This will be the 3rd attempt at replacing the gasket. Having to keep draining the coolant system is getting old - FAST!

Hopefully you did not tweak the new housing. I would check it for flatness before reinstalling.

I found the problem. The new T-stat (NAPA rebranded Stant Superstat) was not seating fully the way I was positioning it in the housing. The top of the NAPA stat is wider and more rounded than the OEM. Also, although the OEM and NAPA stats are the same height overall, the flange of the NAPA stat also sits lower than the OEM causing the top of the NAPA stat to extend deeper into the housing. Depending on how it is inserted into the block, the top will interfere with the housing. I tried this with both the OEM and new (Murray brand) housings. The results were the same. The NAPA stat will fit, however it should be placed with the "V" breathing hole under the "keeper" (don't know what to call it) at the 12 o'clock position. The positioning of the OEM was straight forward as the jiggle pin is located at the 12 position and the flange is marked "UP". I did notice that the flange of the NAPA stat was ever so slightly slightly warped so it was not sitting flush in the engine block, but this may be a result of damage in torquing it down into the housing.

I had planned to post pictures to visibly show the difference, but I don't have permission to post attachments. :dunno:

I will double check the new housing to assure its still flat. I'll also take the OEM stat to compare to a new one (I'm pretty sure I've tweaked the NAPA stat). If a big difference, I'll reuse the OEM.

Hypoid said:

That was my first guess, nevermind how I came to that conclusion. :dunce:

Nevermind how I learned this procedure. :dunce:

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Seeing as how you used this line twice...I'm surmising that you learned this the same way I have learned almost everything working on Jeeps...the hard way...which is actually the best way, because then I don't forget it.

:twak:

I can fully relate and sympathize. Day #4 in thermostat replacement. Using Hypoid's suggestion, I did find a high spot on the Murray branded housing, so I tried re-using the OEM thermostat and housing with a new gasket thinking that maybe I over thunk the whole situation and a gasket was all I needed. Nope. Still had the massive leak from the same area. I now have a new Four Seasons branded aluminum housing. This has a deep outlet area from the water pump that will not cause interference from any T-stat. Initial test fitting last night indicates a flush fitting. We'll see how it goes.

ParadiseXJ said:

Seeing as how you used this line twice...I'm surmising that you learned this the same way I have learned almost everything working on Jeeps...the hard way...which is actually the best way, because then I don't forget it.

:twak:

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Yup!

I tweaked my housing just enough to seep around the lower bolt. My bud went a few steps further and cracked his housing, broke one of the bolts, broke an extractor, and broke a few drill bits on the broken extractor. I convinced him to pull the head and let me work on it. I used a Dremel with a carbide bit to hog out the broken extractor, and most of the bolt. We managed to preserve the threads in the hole.

In both cases, we determined the bead in the thermostat flange was more pronounced, and holding the housing too far away from the sealing surface. We both installed new Stant thermostats and have not had problems since.

Success! arty: No runs, drips or apparent errors utilizing the Four Seasons housing and a new Stant Superstat. Shake down went well and no puddles are forming in the driveway. Even found a local shop to take in some used coolant I had sitting in that garage. I only lost about 1/3 of a gallon through 4 drains of my cooling system with all of the gasket repairs. I used some high tack sealant to hold the T-stat and gasket in place during reassembly and everything went together like a charm.

SWEET!

Thanks for the follow up!

Great that you solved this. This is one reason I just go to the local Jeep dealer for factory parts. They may charge you $15-20 for a thermostat, but its one and done. Faircy Boys will match online pricing from any online dealer & they have all this stuff in stock... anything that will leave you stranded is a stock item... crank sensor, TPS, thermostat, water pump, ignition tune up kit, at least 97 & up. Don't know about earlier years... Not a plug on the dealer, don't work for them or get anything for giving them a thumbs up, just saying I've had good luck with them as a Jeep owner. The Wet Mountains are beautiful. Hope to see you at one of our get togethers!