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Cylinder Valve Broken/Fractured?

Tiny
JDEVRIES64
  • MEMBER
  • 2006 MAZDA 3
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 100,000 MILES
I had been driving down a highway for about 2 hours and then stopped at a rest area and left the engine idling.
While the engine was idling one of the cylinder valves (not sure whether intake/exhaust) broke and fell into the bore of the cylinder.
Of course, the engine wouldn't start and after replacing the battery, alternator (not sure why it was seized), belts the engine still wouldn't start. It was then I saw that the engine wasn't turning over during starting. When I pulled #4 spark plug out, the electrode was crushed, and ceramic was missing.
Using a borescope, I could see the ceramic debris and valve sitting on the top of the piston.

Question:
Can you guide me through cylinder head removal and replacement of the broke valve?
I'm planning on replacing the following being that the engine will be torn apart:
1) All valve guides and seals (intake and exhaust).
2) All valves (intake and exhaust).
3) Reseat new valves (Cut and lap).
4) Cylinder Head Gaskets, Seals and Bolts.
5) Timing Chain.
6) Head Cover Gasket and Seals.
7) Spark Plugs.

What am I missing to check and do?
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Monday, June 26th, 2023 AT 1:18 PM

19 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
Hi,

I attached the directions below for removing and installing the cylinder head/gasket. I would suggest starting here because there could be damage done to the head, the cylinder walls, the piston, and the engine may not be repairable.

Let me know your thoughts on this.

Take care,

Joe

See pics below.
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Monday, June 26th, 2023 AT 10:53 PM
Tiny
JDEVRIES64
  • MEMBER
  • 21 POSTS
Joe,

I agree. I'll pull the cylinder head off to have a look.
I took a video of the inside of the cylinder using borescope through the spark plug hole.
The video is attached and posted on YouTube at https://youtu.be/L979zFD_zLU
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Tuesday, June 27th, 2023 AT 12:11 AM
Tiny
JDEVRIES64
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Joe,

I'll pull the cylinder head off this weekend. Looking at the video above and the crushed spark plug, I think we may be in luck as I suspect that when the remaining stem of the broken off valve impacted the spark plug the engine would have stopped immediately. Had the valve head broken off and rolled around inside the cylinder there would have been more visible damage.
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Tuesday, June 27th, 2023 AT 11:26 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I hope you are right. Was the vehicle at idle or at a high RPM when it happened? Looking at the spark plug, it took a good hit. I just hope it didn't damage the piston or cylinder wall.

Let me know what you find when you remove the head.

Take care,

Joe
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Tuesday, June 27th, 2023 AT 6:40 PM
Tiny
JDEVRIES64
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  • 21 POSTS
The engine was at idle when the valve failed.
I had been driving for 2 hours on the highway (-15°F ambient) and stopped for a break, but left the engine running. I stepped away from the car and on my return noticed the engine not running.
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Wednesday, June 28th, 2023 AT 7:35 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

That makes it a little more promising. Let me know what you find. I'm interested in knowing. Also, if you can attach pics, that would be great.

Tale care,

Joe
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Wednesday, June 28th, 2023 AT 8:42 PM
Tiny
JDEVRIES64
  • MEMBER
  • 21 POSTS
Hi Joe,

After removing the cylinder head, I observed the following:
Exhaust Valve: Broken at the head to stem transition and laying on top of the piston. Break shows evidence of fatigue (worn area as crack propagated) and tensile fracture (fine grain tear of material)
Piston: No apparent damage
Cylinder Wall: No apparent damage
Cylinder Head:
- 2 valve stem impacts around spark plug hole
- 1 impact on intake valve
- 1 impact on exhaust valve seat.
Spark Plug: Impact from valve stem.
Other:
- Intake Valve is offset from its seat indicating that the valve is likely also bent.
- Exhaust Valve seat looks to be bent

It was my intention to replace all of the valves and all of the valve guides.

Question: do you think the cylinder head is reusable if I replace the valve seat AND recut the valve seat bore.

Let me know your thoughts.

Thanks for your help and Happy 4th!

Kind Regards,
Jim
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Monday, July 3rd, 2023 AT 3:40 PM
Tiny
JDEVRIES64
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Hi Joe,

I pulled the valves out and the Intake valve that was off center is significantly bent and its guide had a corner broken off.
I punched out the guide and the head looks fine.

Jim
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Monday, July 3rd, 2023 AT 5:15 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Wow, that doesn't look good. I'm glad to hear there was no other damage. It should be a straightforward repair.

Regardless, thank you for the update. If you need anything, let me know.

Take care and Happy 4th!

Joe
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Monday, July 3rd, 2023 AT 10:35 PM
Tiny
JDEVRIES64
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Joe,

Did you happen to look at my post prior to the report on the bent intake valve?
I had a question about the exhaust valve seat.
Jim
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Monday, July 3rd, 2023 AT 10:38 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Wow! I only saw the last one. The pics are excellent in the prior one. As far as your question is concerned, I don't see why it wouldn't work. If you are replacing the valves and valve guides, you should be able to grind the valve seats. I would start with that just in case you find it can't be done. However, I don't see why it wouldn't.

Let me know if I can help.

Take care,

Joe
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Monday, July 3rd, 2023 AT 10:46 PM
Tiny
JDEVRIES64
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Hi Joe,

Here are some photos of the cleaned up engine block top and cylinder head.
I let the cylinder head soak in Simple Green Pro HD Heavy Duty Cleaner (mix ratio 3:1) for a couple hours and then brushed everything with nylon and brash bristle brushes.
I sprayed Easy-0ff oven cleaner on the piston heads and then wiped off any overspray that landed on the engine block. I let the Easy-Off sit for about a half hour and brushed with a nylon brush. This took some elbow grease but got 98% of it off. I gave up fighting the rest.

I've got new Neway valve seat cutters: Jim (owner) at Neway advised that 30°, 45°, 65° would do just fine in place of the factory specified 35/45/70 Intake and 30/45/65 Exhaust angles.
I'll let you know if the damaged Exhaust Valve seat cleans up.

Questions:
- I'm presuming that the Valve Guide Protrusion Height (see Engine Technical Data) measured from the valve spring seat, correct?
- I'm also presuming I'll need to Inspect and Adjust the Valve Clearance after I'm done cutting new seats, correct?

Kind Regards,
Jim
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Tuesday, July 4th, 2023 AT 4:06 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Wow, you have things looking new. However, now that it is that clean, I noticed the seat has a slight bend. I'm hopeful, but question if you will be able to repair that. Let's see what happens.

As far as your questions are concerned, yes to the valve guide height. The next question related to adjustment; I don't think these are adjustable. The valve tappets are hydraulic and nonadjustable. You are referring to valve lash, correct?

Joe
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Tuesday, July 4th, 2023 AT 10:19 PM
Tiny
JDEVRIES64
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Joe,

I'll give touching up the existing valve seat a try, but my biggest worry is that it might drop out while the engine is running. Thoughts?

I was thinking that if I take the head to a shop and have the valve seat (saddle or seat?) Touched up and replaced with a new valve seat I might have a better chance at success. Thoughts?

Cheers,
Jim
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Wednesday, July 5th, 2023 AT 7:03 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi Jim, I agree with you. I suspect you would have a better chance if it is replaced. I had the same concerns that you have. You may want to take it to a shop and get their opinion. You certainly don't want to do this job twice.

Let me know.

Joe
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Thursday, July 6th, 2023 AT 8:31 PM
Tiny
JDEVRIES64
  • MEMBER
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Joe,

I talked with a couple guys who race and both have said that I should pull the seat, touch up the saddle with a Dremel tool and put a new seat in.
The biggest challenge is overcoming the 0.007" interference fit between the steel seat and aluminum saddle it sits in.
I've heard about heating the aluminum up with a torch and pound the seat out with a slide hammer bearing puller, but I'm worried that will still cause galling of the aluminum saddle. The other method I've seen on Youtube and heard is simply welding a piece of steel to the seat which will cause the seat to shrink during cooling and simply fall out.
I'll let you know how it goes.

Jim
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Friday, July 7th, 2023 AT 7:12 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I have to agree with replacing it. As far as the removal is concerned, remember, steel or metal expands when it gets hot. I'm not sure how welding something to the seat will cause it to shrink. Yes, when it cools naturally it will shrink, but why would it shrink more than what it starts out at?

Let me know. I'm interested in knowing how you make out with this.

Take care,

Joe
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Friday, July 7th, 2023 AT 6:42 PM
Tiny
JDEVRIES64
  • MEMBER
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Hi Joe,

Okay, got the seat out.
We made 1/4" thick plug (with a stem on it) that just fit in the ID of the valve seat. Then we heated the cylinder heat with MAP (approximately 250°F) and tack welded the plug to the valve seat. We then hit the welded in plug with Brake Clean (7-10 second stream) and used a punch and lightly punched the plug and valve seat out of the cylinder head.
As I had said earlier, a number of guys with welding experience all concurred that when welding steel to steel, the parts shrink during cooling.

I wanted to use compressed air but didn't have any at hand. It likely would have worked better as it has more cooling affect. The only thing to watch for is brake clean is somewhat flammable, but seeing we were no longer welding and the parts weren't at combustion temperature, it was fine.

Waiting for a new seat from SBI to arrive. I'll reclean the cylinder head and use a Dremel to dress up the seat counterbore as well as smooth the three spots that got hit by the valve stem.

I'll turn a brass seat punch to drive the seat in square. Then cool the seat in the freezer overnight and warm up the head in the oven to 350°F before pressing it in.

I'll let you know how it goes.
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Monday, July 17th, 2023 AT 3:01 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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You've been busy. Looks good, too. Let me know how things turn out for you. I'm interested in knowing.

Take care,

Joe
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Monday, July 17th, 2023 AT 7:35 PM

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