Broke lower thermostat housing bolt off. Help - JeepForum.com
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post #1 of 18 Old 09-09-2021, 01:02 PM Thread Starter
2003cherokee
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Broke lower thermostat housing bolt off. Help

I was changing the thermostat in the 03 WJ this morning. I broke the lower bolt off about halfway in the timing chain cover. Is there any hope of a quick fix? (probably not)

Anyone know what to do next? Disassemble the front of the beast and take the timing chain cover off?

I can't see anyway of drilling and tapping it. Really tight in there.

It didn't seem tight coming out.

Any help would be appreciated.

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post #2 of 18 Old 09-09-2021, 01:05 PM
juan_carlos__007
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Once you take the other bolt and housing off can you get a very good grip with vise grips and break loose? Spray some wd40 before and let it soak for several minutes. Maybe a bolt bitter socket might help? Take a picture of it.

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post #3 of 18 Old 09-09-2021, 02:27 PM
Soem0
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So you can either pull the timing cover and extract it out of the vehicle or remove the radiator and try to buy you some room. Other option would be hit a pick n pull and snag another cover and do a complete swap
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post #4 of 18 Old 09-09-2021, 11:54 PM
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Unfortunately snapping that lower thermostat bolt is something done too often due to a poor design. It seems like most members in the below thread ended up having to replace the cover. They installed used ones like Soem0 mentioned. Good luck.

https://www.jeepforum.com/forum/f310...-argh-3161393/

2004 4.7L WJ Limited, 96 4.0 ZJ


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post #5 of 18 Old 09-10-2021, 12:21 AM
Delta0
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This tool may help get the stud out.

They need a fair length of stud to grip.
If the stud is not long enough, a dummy stud in the back of the tool may work.
I used the back of a drill as the dummy.

Personally, I'd go for a used part from a scrapper.

https://www.halfords.com/tools/power-tools-and-accessories/power-tool-accessories/stud-extractor-set---1-6mm%2F6-12mm-2pc-208318.html?istCompanyId=b8708c57-7a02-4cf6-b2c0-dc36b54a327e&istFeedId=367c5610-f937-4c81-8609-f84582324cd6&istItemId=ittamtrxi&istBid=t&_$ja=tsi dcid:11902546034|agid:113456751337|tidla-330911374943|crid:487900199209|nw:u|rnd:1717697386 7196114555|dvc:c|adpmtloc:1007201&gclid=Cj0KCQ jw4eaJBhDMARIsANhrQAB_KQqMT5DEl3RlOqbxK4L13WyKN0LW 4sXSynOe6nP5zT4kUwWg3JEaAil5EALw_wcB
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post #6 of 18 Old 09-10-2021, 09:45 AM
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Quote:
Originally Posted by 2003cherokee View Post
I was changing the thermostat in the 03 WJ this morning. I broke the lower bolt off about halfway in the timing chain cover. Is there any hope of a quick fix? (probably not)

Anyone know what to do next? Disassemble the front of the beast and take the timing chain cover off?

I can't see anyway of drilling and tapping it. Really tight in there.

It didn't seem tight coming out.

Any help would be appreciated.
Been there, done that 2X. Welcome to jeep world. Would like to meet the arse that 'designed' that.
Getting a used cover is a bad idea. Get a plastic replacement because they have a recess inside the housing to accommodate the thermostat, as opposed to the original ones that did not (at least that was the case on my two 04s, 4.7L). They relied on the alignment and force of the two mating surfaces to make a secure/leak proof fit....another *really stupid* design.

IF any of the bolt is showing, douse it with lots of rust penetrant, let it sit for a while, then use needle nose vise grips to try and rotate it.
I went and purchase a Milwaukee right angle drill and was able to drill it out. You can either retap it or just use a SS bolt & nut.
I had to cut a drill bit to shorten it so I could get the drill in....really tight.
IIRC, Dremel makes a small right-angle attachment that can be used with their flex cable that would probably work as well.
In a pinch, you can use a C-clamp to hold it together if you need to use the vehicle.

This is such an aggravating thing...something so simple is cocked up in multiple ways....
good luck
J
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post #7 of 18 Old 09-10-2021, 10:02 AM
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The thermostat on my wj has not benn touched since the wj has been assembled....

I wonder what could happen trying to unscrew that bolt....

As said by @DoubleE , probably it is better to put periodically WD40 on the rear of that bolt (I think it is not a coincidence that they have designed the through hole)

Grand Cherokee WJ 4.7 V8 HO. m.y. 2002
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post #8 of 18 Old 09-10-2021, 12:00 PM
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When I changed my thermostat and water pump for the first time on my 04 4.7 a few years ago I had already read how easy it was to snap that lower thermostat bolt. Steel and aluminum don't like each other anyhow then add a bunch of road salt to the mix while the bolt was seized in big time.

I used my torch on the timing chain cover where the bolt threads were inside and then between heatings shocked the bolt area with PB blaster. After doing this a few times when the aluminum was hot/expanded the bolt finally broke loose. Tight place and you have to watch since aluminum melts at low temps but have had to use my torch to loosen bolts/nuts up in tight places before.

I too was thinking about using a 90 degree drill if the bolt breaks while good tip about dremel makes one for their extension cable.

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post #9 of 18 Old 09-10-2021, 01:23 PM
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@Uniblurb , how did you succeed in not melting the plastic thermostat housing with the torch?

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post #10 of 18 Old 09-10-2021, 02:00 PM
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@mak_v8 , I may have been using my thin tipped brazing torch but could have just been my propane torch which was more convenient. Regardless the heat did not phase that plastic thermostat housing with me pointing/moving the heat at the aluminum where the bolt threads are. That housing must be made of some special plastic compound.

I priced an aftermarket thermostat housing beforehand at a local parts store since they say to replace it with the thermostat. But I used used the OE one and it never melted or leaked.

PS. It was my regular propane torch I used to heat that thermostat housing bolt area from underneath and below is a real wordy write-up from 4 years ago.

https://www.jeepforum.com/forum/f310...4-7-a-4216306/

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post #11 of 18 Old 09-10-2021, 02:19 PM
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Since the timing cover is aluminum, you could potentially get a flux core/MIG welder in there and build up some welds until you get enough weld protruded to grab on to. Perhaps some copper tubing to help direct the welds? It won't stick to the aluminum very much, but will definitely weld to the bolt shaft. I've used this trick before in getting broken bolts out of holes. Definitely higher on the skill level, and in that tight spot, I dunno if it's feasible, but it's an idea.

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post #12 of 18 Old 09-11-2021, 12:23 AM
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Quote:
Originally Posted by jw11432 View Post
Since the timing cover is aluminum, you could potentially get a flux core/MIG welder in there and build up some welds until you get enough weld protruded to grab on to. Perhaps some copper tubing to help direct the welds? It won't stick to the aluminum very much, but will definitely weld to the bolt shaft. I've used this trick before in getting broken bolts out of holes. Definitely higher on the skill level, and in that tight spot, I dunno if it's feasible, but it's an idea.
Have you tried welding a nut onto a broken stud yet Jw?
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post #13 of 18 Old 09-12-2021, 09:46 AM
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I have.

Quote:
I've used this trick before in getting broken bolts out of holes.

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post #14 of 18 Old 09-13-2021, 06:16 AM
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If you have a weldor hit the actual stud with a zap real quick to get some quick heat in it if you can, it may break it loose. A different circumstance however to remove pressed in steel bearing races out of aluminum hubs a quick zap on the face of the race and they literally fall out. The heat expands the steel so fast it breaks the bond to the aluminum.
If you cannot get it out and can get the cover removed find a shop that does EDM, they can get it out in a minute, probably cost less than a used cover. I used to use this method often when a bottom bracket is seized into a high dollar bicycle frame (Ti, carbon fiber), usually cost around $50 bucks.

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post #15 of 18 Old 09-14-2021, 06:36 AM
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I have.
Thanks JW, how successful were you please?
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