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Thermostat Housing Leaks 5.7 Hemi

17K views 24 replies 7 participants last post by  90grandoneer 
#1 ·
Has anyone else had persistent thermostat housing leaks on their 5.7's and, if so, how did you fix it? I'll bet I've replaced the thermostats (that's the only way I've found that you can get the seal) and seals no less than 6 times over the past 10 years....3 times on each of my Hemi's. I've tried new seals/thermostats, gaskets, gaskets/seals/RTV and nothing seems to work over the long run. Just noticed that my LX was a little low on coolant, so I hooked up my pressure tester and it immediately started leaking from the thermostat housing. Is the fix a new housing or ???? Also, does anyone know where to get just the seal without having to purchase the thermostat too?
 
#2 ·
Any auto parts store should be able to get the seal separate from the thermostat. You have 1 of 2 problems. Either the coolant leak is not from the thermostat seal, and is another coolant leak running down into that area and you are not seeing it, or your completing the job, and your workmenship is only lasting a little bit of time.

The seal is not unique to the jeeps, meaning all those hemi's out there run the same oring/seal setup, so getting just the oring/seal should be easy. I did mine about a year ago, and I believe I purchased the seal, found the thermostat damaged after disassembly, and ended up going back for the thermostat. I purchased my parts from advanced auto parts.
 
#3 ·
Nope, no auto parts store in my area will sell a seal separate from the thermostat and they don't show a listing for it. Also, the leak is coming from the housing like it does every time, as it's easily seen and very obvious when I pressurize the system. No guess work here. Not likely to be workmanship either as I've been working around automobiles probably longer than most forum members have been alive. I do know how to correctly install a thermostat and properly torque the housing. It's certainly not rocket science. I've been over on the Ram forums and quite a few over there have had similar problems. Just want to know if anyone has had the issue with the WK's, even though this issue is on my LX.....same exact setup though.

I don't think there is an Advanced Auto Parts near me, but I'll take a look on their website and see what I come up with. Thanks for your input, I appreciate it.

Edit: Just went over to Advanced Auto's website to see if they have a listing for the seal. Here's what came up:
"Sorry, we didn't find any results for your selected vehicle."
 
#4 ·
Over on the Ram forums some are saying the problem is the thermostat cutting into the rubber seal because of being either slightly oversized or having sharp edges that cut the rubber seal. Both of mine have Napa Auto 190* thermostats in them and have for years, so this time I'll be taking a real close look at the thermostat too.

Edit: Also looked around on some of the other DCX/FCA forums and found this happens fairly often with the Hemi's, but many of them occur when aftermarket thermostats are installed or when the weather is real cold. Both of mine fall into this category......aftermarket thermostats and the weather has been and is going to continue to be 20* F and below for the next week or so.
 
#5 ·
My OE one leaked at about 85,000 miles (about a year ago). When I pulled it out you could see that orange seal gets slightly deformed. I put in an OE stat and it has not leaked again.
 
#6 ·
my 07 wk hemi leaked around the tstat housing ever since I got it. when I replaced the alternator, I had to remove the upper hose so I replaced the tstat. when I had the housing off I noticed a sharp edge on the inside of the housing where the o ring fits in so I took some emery cloth & smoothed it out. that was about 2 weeks ago & so far no leaks. that may help you. good luck
 
#7 ·
Thanks guys. I'll turn the heater up in the garage tomorrow and at least tear it down and see if I can see what's going on. Because this has happened on both my Hemi's though, I am hoping it's the Napa Auto thermostats or the seals that they use. I do remember a while back I put a factory (203*) thermostat in it and I never had any problem again until after I changed back to the 190* Napa unit. I'll report my findings, if any. For giggles, I'll also check my maintenance records to see exactly how many times this has occurred on each vehicle.
 
#8 ·
Hmmm heated garage.....lucky guy.....
Been freezin in the driveway all these years....
BTW as a maintainer of salt water boats I've been using OMC/Bombardier gasket sealer on things like thermostat bolts. Same thing as Permatex Aviation Sealer. It seals out corrosion and never hardens. I use it on thermostat bolts, all the bolts on the outdrive that sits in salt water and exhaust manifold bolts (inboard marine exhaust is water cooled and should not get hotter that 150*). Works well on water pump bolts as well. No worries about galvanic corrosion as can happen using antiseize if there are stainless bolts going into aluminum.
 
#9 ·
LOL, Lou! Yes, it is nice in the winter. I keep it at 45* in the winter. I also have a drive on Bend Pak Hoist which allows me to work on almost everything. It'll lift the vehicles up about 3 ft. in 30 seconds or so. I've had this setup for about 18 years now, gave my first hoist to my son for his business and found I couldn't live without so bought another one. This hoist is only about 3 years old and not as good quality as the first one. This one was made in China though.

I'll have to bookmark your post, as those sealants sound like they really do the job if it's used in salt water. The only marine stuff I've ever used was called MarineTex. Don't know if they even still make it but, as I recall, it was like an epoxy sealant that you could drill, shape, tap and that sort of stuff. Anyway, thanks for the info.

Joeyicu, I found a CarQuest place about 7 miles away. I guess they're the same as Advanced Auto. Their website shows they have a thermostat/seal in stock for $20, so I think I'll give them a try. Never used them before and didn't know they were even there. Thanks again for your info.

Because of the cold weather and the fact that I don't drive the LX too much in this environment, I'll just take my time and check everything real closely. I think I still have an old stock thermostat laying around and I'll be checking dimensions with a digital caliper, and look for sharp edges, as well as really check out the seal I pull out. Who ever thought a thermostat would be such a big deal.
 
#12 ·
Yes, the seal I got was a car quest part from advance auto. I purchased this before I tore the truck down and found the thermostat damaged. I dont remeber it costing 20$ but maybe it did and I was like 'oh well'. I'm running a Sloan (180* maybe?) in mine
 
#10 ·
I noticed the smell of coolant last year when I was walking past the front of my GC hemi. It was the t/stat housing as well. I noticed some rust on the housing, so I replaced the housing and the t/stat. No more leak!! The housing was under $20.00 right from Jeep, if I remember correctly...... Take a good look at your housing.
 
#11 ·
Well, I pulled it apart and the worst part of the job is getting those damn plastic rivets out of the lower bumper cover on the LX to gain access to the radiator drain valve. Pulling the thermostat takes all of 3 minutes once you've drained a little out of the radiator and removed the bleed plug.

As I said above, I'd check my records to see how many times I've done this between my two Hemi vehicles. It's been done 5 times in 55,000 miles on the WK, including the stealer doing it just before I bought it a little over 6 years ago. Granted, two of those times were once when I changed the camshaft and once when I removed the stock 203* unit in favor of the 190* unit. The LX (the one that was now leaking) has only been opened up 3 times in almost 78000 miles, once when I first installed a 190* unit, once when putting a new one in when I changed the camshaft, and now this time.

I've also found an old factory 203* thermostat (PN 52028898AE)....most online places call this Chrysler part number a 195* unit, but 203* is stamped right on it. Anyway, I checked it's dimensions (thickness and diameter) with the aftermarket Napa unit, as well as the seal conditions and thicknesses, the thermostat housing for flatness, and the depth of the recess in the front cover. Without going into all the dimensions, I'll say that everything was close enough between the two so, by themselves, wouldn't cause any issues. The aftermarket (Napa) used seal was .005 in. thicker than the used factory one. Any irregularities in the used rubber seals were all on the thermostat housing side, not the front cover side.....which looked pristine on both seals. The front cover recess (where the seal sits) was about .035-.040 in. shallower than the used seals so the seals, in theory, should seal properly. The thermostat housing is a little rough (stamped metal) on the rubber seal mating surface and not completely flat when checked with a straight edge. So, from what I can tell, the housing is the most likely culprit. Cobra259 and nvrdone1, it looks like you guys might win the Kewpie Doll prize.

Tomorrow, or when the weather improves and warms up a bit, I'll go get another thermostat and seal, take the measurements of both, and try to find an aftermarket housing that is made a little better than the factory one. Kind of interesting stuff for such a simple setup.
 
#14 ·
The thermostat seal is now available (for years it wasn't) by itself. Here's the part number: Mahle P/N C31788. Of course none of the parts places near me carry them so they would all have to special order it. As a result, I bought another thermostat (~$16) that came with the seal. I then came home, plugged the seal part number into the search engine and found that RockAuto had a closeout on them for $1.10 each. Since I've had so many problems with this on both my Hemi's I bought 6 of them. I'll be using two of them when I get my Billet Technology thermostat covers after the first of the year. Installing them should eliminate any future housing leak problems.

I am 99.9% positive that the problem with mine leaking was the cheap stamped metal cover they use. I ended up "lapping" the mating surface, and it needed quite a bit to get it to the point where the surface was totally flat. I tried to buy one of those at the parts place too (Murray P/N 85341) but, of course, they didn't have it in stock either. Hence the need to lap the old one.

I put the whole thing back together and pressurized the system for ~20 minutes without it losing any pressure. If the weather is a little better tomorrow I'll drive it a bit and then top off the coolant, if needed.

Thanks for everyones' input.
 
#15 ·
I'll take credit for thinking it is the thermostat housing/outlet casting also.....even though I'm late in responding. One issue with the cast housings is that they warp if torque on the 2 ears is too high for the pot metal. Lapping/sanding it flat (across the ears) could cure it. Clean off any casting flsh at the gasket mating surface also.
My stock thermostat is running the coolant between 190-194 degrees F in the sub-freezing weather.
 
#16 ·
Hi Walt! Are you on Christmas break? Haven't seen you on here in a while. You've got 152K on yours now....that's great. You're really piling them on. I am just over 104K now....only 10-12K a year, at best. How's yours been running now?

After a day with the "lapped" housing it seems to be holding. I've kept my pressure tester hooked up to it overnight and it seems to be holding real well. I've also ordered the Billet Technologies thermostat housings for both the Hemi's. I am hoping I'll never have to do the job again after I install them.
 
#19 ·
Heep has been running well with new lower ball joints, tires, and turn signal stalk. :smile2: Radio just went out (all RHS speakers inoperative). :mad: Rear set cup holder plastic piece broke (inside housing) and the new one costs ~$210. :thumbdown: I'll wait on that.

Now teaching engineering (thermodynamics & heat transfer) to stay out of trouble.

Glad the lapping is holding. Those pot metal housing warp easily. :frown2:
 
#17 ·
I am glad that is all settled now. Good deal on the repair. The more I own my Hemi wk the more I regret having picked a hemi over the 4.7 with all the hemi related issues my wife has had driving the thing. I don't think the power gains over the 4.7 are worth the headaches.
 
#20 ·
Billet Tech. has finished a new run of thermostat housings and I got my two today. Ordered them back in mid-December and I will say they were worth the wait. I would be really surprised if I ever have a leaking thermostat housing again after I install them on both of my Hemi's. Check out the quality.
 

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#23 ·
#24 ·
you can barely see that thing. Colors seems silly. I guess if mine ever starts leaking again I will pick one up. I thought you most recent repair held and wont have any issues?
 
#25 ·
I agree on the colors being a waste of $$$.

I haven't driven it since I "lapped" the original, but it does hold pressure overnight without any loss and the original was far from being flat on the mating surface. I am just tired of having to redo them on both my Hemi vehicles, way more often than I should have to.....which should be never.

The weather has been crap since mid-December and now the snow plows have a big berm in the part of the driveway behind Maggie. We're suppose to continue getting storms one right after another for at least the next week so, within that time, I'll turn the heater up in the garage and install it. I have the WK for this type of weather and I don't usually drive the LX much anyway this time of year, unless the weather is nice. It's my fair weather baby, LOL.....12 1/2 years old and only 78K on it. I'll put the one on the WK toward springtime when it warms up a bit.
 
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