Stripped socket for timing chain cover bolt

When I did my head gasket job several years ago, I cut a corner and acted against my better, more conservative and circumspect judgment leaving one timing chain cover bolts in a stripped socket, meaning tight enough just to stay in but spinning endlessly on greater torque. I thought because there are so many (20+) bolts in the cover, it would be OK, especially with ample gasket maker.

Soon after the job, I realized the engine was losing oil, something like 4 qt per 1000. The truck ran fine as long as I kept adding oil, did longer trips and everything. That bolt was one of my suspects during that time but I was also fretting I had bungled the head gasket job.

I am now working on something else (VVT sprocket replacement), which could have been done without taking the whole cover off but I decided to do it to try to address the oil loss issue. I discovered a lot of oil gunk and buildup around the bottom of the cover, in the vicinity of the faulty bolt.





That bolt is one of the picture left one of the two unlike the rest of TC cover bolts in that it is a stud bolt with a male star head (meaning it needs a female star socket) and it gets a nut over it. You first put the stud into the engine block socket, then they can be used to guide the cover into the exact location, then you put the nut over it. The picture shows the stripped socket bolt with the nut on the left and the other one of the same kind on the right without the nut, head exposed.



Here is a picture of the bolts only. Notice how the one from the stripped socket is visibly darker.



The bolt shaft is the same size as all the other TC cover bolts, 12 mm 6 pt nut.. It appears to me that I need to tap the socket wider and insert an adapter that fits this bolt.

QUESTION: What is the spec of this bolt, meaning shaft diameter? Is it 6 mm? The spec I have shows only the torque but no bolt specification, such as the length, shaft, and head type. It is unusually difficult to Google the specs for these bolts or find them in the manual. Basically, which size HeliCoil should I get?

 

If you bring your fastener to any COMPETENT hardware store, they’ll hook you up. Before you go to drilling and such, make certain they gave you the correct size and thread pitch by sticking the insert onto your fastener.

I urge competent. You ask someone at the orange store for a helicoil kit, the likely answer will be wuzzat?

I have several thread repair kits. Helicoil is good but the insert is like a spring. One kit I have for m12 2.0 is made by I think they’re called timeco. The insert is more of a tube with threads inside and outside, a better design.

If when you drill and go slightly off center, getting the cover back on may be a problem. Test fit without the gasket glue first. If that hole won’t align to the repaired hole you might need to massage the cover hole with a rat tail file, die grinder, or drill.

Best of luck.

 

It's probably 8 x 1.25

 

I actually just took the time to find my digital caliper and measure the bolt. It's a 7 mm diameter

 

I am trying to order online. Like I said in a previous comment, I ended up measuring it.

 

7 is an odd size. Remeasure. Really, you also need a thread pitch gauge. 8 1.25 is very common and probably correct.

 

There is nothing 7mm on a toyota. It's all 6/8/10/12 X 1.0/1.25/1.5

 

This is not the exact bolt but it's the same diameter/pitch size

 

I hear you but that's the measurement I am getting. Maybe my caliper is wrong. I am also surprised we can't find an official Toyota spec for it, like we can for torques.

 

Any parts store or hardware store could match up a metric bolt. That looks like 6x1.0

 

But I am not showing length, only the diameter and it is clearly measuring 7 mm. In fact, the analog scale on the caliper is showing 7 mm, not just the digital, so it's not like a digital malfunction.

 

Does anyone know if the Haynes manual, and in which section, shows these specifications for each bolt in the engine? I mean, that has got to be somewhere.

 

Imagine the bolt threads, mountains and valleys. Your measuring the valleys, incorrect. You need to measure the mountains.

 

The internet isn't going to sleuth this one out for you

Take the bolt to a store, it's a super common size, they will have it. Lowes/HD/OReilly/Napa

 

It doesn't have to be exactly 6mm to classify as that size. Kind of how 2x4s aren't always exactly 2 inches thick but it's still called a 2x4

 

At least for 2x4 I know the conversion rate. How do I convert measured 7 mm to whatever the marketing size is?

 

By taking the bolt down to a store

 

This or measuring it correctly

 

I stand corrected. I thought I was measuring mountains before but it was valleys. Here we go, 7.85, so I guess that makes it an 8 mm bolt.

 

What does 1.25 represent? Is

Highking Tool Thread Repair Kit, M8 x 1.25 mm Metric Thread Repair Insert Kit Compatible Hand Tool Set for Auto Repairing M8-1.25

this the kit I need: