Just letting folks know about my experiance of what happened and what I did when I snapped the injector bolt of my 175k 05 'scrap yard dodging' Accord.
Removing injectors proved pretty easy - just slacken off the clamp screw by half a turn and run the engine. Remove the fuel line, leak back pipe and cable, and when the clamp is fully removed the injector will turn slightly back and forth and can be slid out.
The problem was that after doing 2 injectors, on replacing the third I snapped the Torx T30 bit of my 1/4" socket set, and so went and bought a long bit for my 1/2" socket set. Big mistake, as it was now possible to over tighten the bolt, which is a pretty flimsy M5 'stretch bolt' with a long shaft before the threaded section to give the clamp some spring tension. After 10 years and 175k miles, these bolts are pretty tired, and mine snapped off just into the threaded section, deep in the engine. First thoughts were that that was it, and the scrap yard can be dodged no more. However, seeing as I had nothing to lose, I stripped the engine down to expose the head by removing the rocker cover. A bit of a job:
- power steering pump pipe
-oil feed pipe
- all the injectors and high pressure pipies,
- a couple of brackets at the side and back
- lots of sensor connections
- remove the 6 screws and wiggle it all out.
This revealed the head, cam shafts etc in all their oily glory.
The holes where the injectors and clamp bolts go are raised columns, with little rubber seals around them which seal them to the gasket cover.
First I tried screw extraction. Starting with a large bit drill bit, wrapped with masking tape to keep it centred in the hole, to try and make a cone in the remanents of the screw. Then drilled a pilot hole with 3.5mm bit and tried to get the screw extractor to bite. As we all know, screw extractors don't work ( a lesson which should be given to all secondry school kids along with the other facts of life), and if you snap the extractor in the hole, then you have something undrillable! So I gave up on plan A.
Plan B was to tap out the hole to the next size up and fit a bigger bolt. There is a lot of column between the face where the clamp goes and the threaded end which is filled up by the lost end of the bolt. Where mine had snapped, a full 50mm M7 allen key bolt would fit perfectly, and the existing hole was just about the right size for tapping to M7 - a little bit larger than perfect, bit hopefully with enough meat to take a thread. The alternative would be to drill it out for an M8 (6.8mm I think). The M7 tap ran out of depth before reaching the bottom, so I drilled out about 10mm at the top to 7mm diameter so that I could bottom the tap and use as much of the screw as possible, rather than shortening the screw.
So far so good. Next job to drill out the Clamp to 7mm. Easier said than done. Honda has decided to make these clamps out of a cryptonite-***anium alloy that none of my tools would scratch! At this point I went to get some help (thanks to the guys at Cambridge Rebores!). The only way to drill this, is to heat it up with a blow torch until it glows red, and then drill away. Even then it took 3 heat ups and much resharpining of drill bits. A tenner and a useful lesson later, I had my modified clamp. Incidentally Cambridge rebores do a lot of converting Merc injector clamp fixings to M8, so a common issue!
Its all back together and all the injectors have been gingerly tightened. A small leak on the modified, but I really didn't want to stress the not quite deep enough threads on my new M7 hole. I will keep tightening until the leak stops.
I stripped rocker cover off to do this, but this really isn't necessary, if you get an extender for your M7 tap. Only thing to note is that the injector hole and the clamp hole are inside the same rubber seal under the rocker cover, so swarf would go into the engine if you dont block off the injector hole somehow. Also, lots of grease on the tap will collect the swarf.
Another tip I got was to anneal the copper washers to soften them before re-use. Just heat them up with a blow torch and let the cool.
Removing injectors proved pretty easy - just slacken off the clamp screw by half a turn and run the engine. Remove the fuel line, leak back pipe and cable, and when the clamp is fully removed the injector will turn slightly back and forth and can be slid out.
The problem was that after doing 2 injectors, on replacing the third I snapped the Torx T30 bit of my 1/4" socket set, and so went and bought a long bit for my 1/2" socket set. Big mistake, as it was now possible to over tighten the bolt, which is a pretty flimsy M5 'stretch bolt' with a long shaft before the threaded section to give the clamp some spring tension. After 10 years and 175k miles, these bolts are pretty tired, and mine snapped off just into the threaded section, deep in the engine. First thoughts were that that was it, and the scrap yard can be dodged no more. However, seeing as I had nothing to lose, I stripped the engine down to expose the head by removing the rocker cover. A bit of a job:
- power steering pump pipe
-oil feed pipe
- all the injectors and high pressure pipies,
- a couple of brackets at the side and back
- lots of sensor connections
- remove the 6 screws and wiggle it all out.
This revealed the head, cam shafts etc in all their oily glory.
The holes where the injectors and clamp bolts go are raised columns, with little rubber seals around them which seal them to the gasket cover.
First I tried screw extraction. Starting with a large bit drill bit, wrapped with masking tape to keep it centred in the hole, to try and make a cone in the remanents of the screw. Then drilled a pilot hole with 3.5mm bit and tried to get the screw extractor to bite. As we all know, screw extractors don't work ( a lesson which should be given to all secondry school kids along with the other facts of life), and if you snap the extractor in the hole, then you have something undrillable! So I gave up on plan A.
Plan B was to tap out the hole to the next size up and fit a bigger bolt. There is a lot of column between the face where the clamp goes and the threaded end which is filled up by the lost end of the bolt. Where mine had snapped, a full 50mm M7 allen key bolt would fit perfectly, and the existing hole was just about the right size for tapping to M7 - a little bit larger than perfect, bit hopefully with enough meat to take a thread. The alternative would be to drill it out for an M8 (6.8mm I think). The M7 tap ran out of depth before reaching the bottom, so I drilled out about 10mm at the top to 7mm diameter so that I could bottom the tap and use as much of the screw as possible, rather than shortening the screw.
So far so good. Next job to drill out the Clamp to 7mm. Easier said than done. Honda has decided to make these clamps out of a cryptonite-***anium alloy that none of my tools would scratch! At this point I went to get some help (thanks to the guys at Cambridge Rebores!). The only way to drill this, is to heat it up with a blow torch until it glows red, and then drill away. Even then it took 3 heat ups and much resharpining of drill bits. A tenner and a useful lesson later, I had my modified clamp. Incidentally Cambridge rebores do a lot of converting Merc injector clamp fixings to M8, so a common issue!
Its all back together and all the injectors have been gingerly tightened. A small leak on the modified, but I really didn't want to stress the not quite deep enough threads on my new M7 hole. I will keep tightening until the leak stops.
I stripped rocker cover off to do this, but this really isn't necessary, if you get an extender for your M7 tap. Only thing to note is that the injector hole and the clamp hole are inside the same rubber seal under the rocker cover, so swarf would go into the engine if you dont block off the injector hole somehow. Also, lots of grease on the tap will collect the swarf.
Another tip I got was to anneal the copper washers to soften them before re-use. Just heat them up with a blow torch and let the cool.
