Hi: Recently needed to replace thermostat in my 1990 Camry. Nut on the right hand side was very difficult to get at, but I managed to get it unscrewed. Problem: I overtorqued the left nut and the bolt snapped off! Can I bore out the entire nut (it seems to run right through the entire housing and out the other end)? Or do I have to replace the housing the bolts are mounted into?

Any help would be most appreciated.

-Mike

 

This a V6?

If the nut broke off, the stud it screws onto threads into the housing behind the inlet fitting.

Where did the stud break off, flush with the housing?

You can drill out the stud or try an easy out/bolt extractor. When drilling make sure the new hole is centered on the stud (in the center of the hole the stud screws into).

Don't use to big of drill or you will remove the threads on the housing.

Worse case if the housing threads are damaged beyond use, a Helicoil, etc to repair them.

 

Ok. Sounds good. It's a four-cylinder and the stud snapped off pretty much flush with the housing. When I remove the damaged stud, where can I get a new one to thread in?

Thanks,

-Mike

 

The internet would have sites selling metric studs.

Local auto parts and machine shops maybe or they might give you advice as to where to look in your area. Broken studs are not uncommon.

You can make a stud from a metric bolt by cutting off the head and treading the head area. If you don't have metric dies cut English threads and use the correct threaded nut.

 

Ok, thanks for the help!

Cheers,

-Mike

 

Appreciate the advice but on account of my inexperience I have some questions:

-on the Helicoil: I suspect 'Helicoil' is the trademark name for a device that somehow repairs damaged threads. Not sure!

-"treading the head": I think this might refer to buffing/grinding/smoothing the freshly cut end of the bolt so as to allow the nut to be threaded smoothly onto the stud. ???

-re: "metric dies": pretty sure you're referring to a tool & die kit, which is used for ???? I've heard of them, just never learned what they're used for!

Just wondering,

-Mike

 

Helicoil is trademark name.

The purpose of threaded inserts can be to replace damaged threads with new threads via the insert, reinforce a material that may not be strong enough to withstand bolt pull out forces it encounters, or provide thread protection in case of repeated bolt removal.

A part made of aluminum may have a threaded insert installed a time of production to increase the amount of force the bolt can apply (tighten up the bolt more) or the bolt may be removed and replaced a number of times which over time can lead to thread damage and failure.

There are differences in the insert design and installation.

The Helicoil design is not one that is recommended for this repair job, Time-Sert (trade name) is.

A tap cuts threads into the side of a hole. Drill a hole in a thick piece of metal. A tap of the right diameter will cut threads into the sides of the hole for a bolt to thread into.

The tap is self-threading. The snout of the tap is tapered to allow the tap to slowly bite into the material as it is rotated and pull its way in. The hole diameter needs to match the tap diameter to obtain optimum thread strength. If the hole were too large for the tap obviously the cutting threads on the tap would not cut much off the hole walls. Too small a hole can results in too much material being cut off.

For the Toyota engine, the old threads in the block are damaged (the bolt threads made of steel pulled out of the block threads made of aluminum).

The damaged threaded hole in the block is drilled out to a larger hole diameter then a tap used to cut new threads. Once done the insert is installed.

The insert being make of steel and having a larger gripping area in the block (the insert threads are larger diameter then the head bolt thread diameter and have more gripping area contact with the block) will stand up better to the forces the bolt encounters.

A die cuts threads around a round bar. Take a bolt and cut off the threaded portion. A die of the correct size can be used to cut new threads around the bolt shank.

The die has a larger threaded hole diameter on the side that cuts the threads. This allows limited engagement of the die cutting threads until the die has started to fully engage the material.

Threads are defined by type, ISO metric or UTS (typically what is used for US manufactured goods), pitch (number of threads per inch) and diameter (10 mm, 12 mm, 1/2 inch, 1 inch).

There are other types of threads but those stated are the most common. Threads types can have the same diameter but a different pitch.

Threads size, pitch, diameter, etc are standardized and controlled by various organizations. As such everyone uses the same standard and no surprises.

 

Wow! Thanks for the detailed response, I appreciate it!

Cheers,

-Mike

 

I finally got around to removing the broken stud. It was much easier than I had anticipated; I clamped a pair of vise-grip pliers on the broken end and to my delight it threaded out (slowly but steadily).
Accessibility was a major problem so I removed the alternator, which created a lot more space to move around in. Much easier access!
Now, to find a replacement stud with the right threads. I am wondering if the studs from my parts car, a 1989 Camry, would fit. Do you think they would??? Although, it might be less of a hassle to search around town.

-Mike

 

You will need to check the length and diameter of the one on the parts car.

Can also replace the stud with a metric bolt of the correct length and dia. This may be easier to find as many hardware stores sell metric bolts.