M20 Seized Cam

[ThatM20Guy]

I have a question for all you experienced m20 guys. I can't seem to find a case of the same thing happening. And before I go into detail the car had fresh fluids and all.

I recently had my m20 decide that it was tired of life and break a rocker and bend a valve. The car sat for probably 2 weeks since the last time I ran it. It was running well for about 2 minutes before it just stopped. It seems like the cam seized and that was what caused the problem. Disassembled the head and the cam gear won't budge. This left me questioning the oil flow to the head.

Is this a one off problem of have y'all heard of this before?

My only ideas are a blocked oil passage to the head, failed oil pump, or shot bottom end bearings.

I am already rebuilding a fresh head but any input before I get worried about destroying a new head and pull the motor to rebuild?

Any input is appreciated

Rob

[ThatOneEuroE30]

If the head was really warped the cam could get stuck. Otherwise it not getting oil could cause it to grind into the journals and get buried in the cast aluminum. If it was me I’d be pulling the bottom end and rebuilding it. Make sure you put new rotors in the oil pump and it it all cleaned out if you go that route.

[ThatM20Guy]

If the head was really warped the cam could get stuck. Otherwise it not getting oil could cause it to grind into the journals and get buried in the cast aluminum. If it was me I’d be pulling the bottom end and rebuilding it. Make sure you put new rotors in the oil pump and it it all cleaned out if you go that route.

Thanks for the response! I don’t believe the head was warped in any way. Only problem was a super slow seep in the headgasket. I am planning on just getting a whole new oil pump to not put anything to chance.

[ThatOneEuroE30]

Thanks for the response! I don’t believe the head was warped in any way. Only problem was a super slow seep in the headgasket. I am planning on just getting a whole new oil pump to not put anything to chance.

You could probably save a couple bucks by just replacing the rotors and giving it a thorough cleaning

[ThatM20Guy]

You could probably save a couple bucks by just replacing the rotors and giving it a thorough cleaning

OK I'll look into it!

[ThatOneEuroE30]

OK I'll look into it!

If the cost pf new rotors is too much let me know. I have a set of good used ones in my tool box at work. I put a bunch of cash into my engine and didn’t wanna skimp on one thing so just got new ones even though mine were fins.

[zaq123]

Once all rocker shafts were removed, cam still doesn't spins? Were you able to remove all rockers/rocker shafts without rotating the cam? Just trying to understand the problem. Also to properly rebuild the oil pump, you would need to machine the housing again. The flat area where gears are riding, gets scored and this results in some pressure drop.
If you concerned about the oil pressure, I would pull the intermediate shaft and give its bearing a good look.

I honestly don't see how seized cam can brake a rocker without any damage to the timing belt. Rockers are driven by the cam. If cam get's seized, TB will strip some teeth and pistons would hit the valves and valves would possibly break the rocker. That would be one ugly damage to the engine.

On my VW TDI with ALH engine (miss that car), I had seized water pump once and TB had good 6" of shaved teach, bent valves and no damage to pistons. I was so pissed, sold the car the next day and still regret it

[ThatM20Guy]

Once all rocker shafts were removed, cam still doesn't spins? Were you able to remove all rockers/rocker shafts without rotating the cam? Just trying to understand the problem. Also to properly rebuild the oil pump, you would need to machine the housing again. The flat area where gears are riding, gets scored and this results in some pressure drop.
If you concerned about the oil pressure, I would pull the intermediate shaft and give its bearing a good look.

I honestly don't see how seized cam can brake a rocker without any damage to the timing belt. Rockers are driven by the cam. If cam get's seized, TB will strip some teeth and pistons would hit the valves and valves would possibly break the rocker. That would be one ugly damage to the engine.

On my VW TDI with ALH engine (miss that car), I had seized water pump once and TB had good 6" of shaved teach, bent valves and no damage to pistons. I was so pissed, sold the car the next day and still regret it

Oh the timing belt did have all the teeth shaved off that contact the crank pulley. This led to a bent intake valve on #4 and a broken rocker on intake of #6. There's really no damage to the piston tops thankfully.

[zaq123]

Oh the timing belt did have all the teeth shaved off that contact the crank pulley. This led to a bent intake valve on #4 and a broken rocker on intake of #6. There's really no damage to the piston tops thankfully.

yeah that definitely sucks. Were you able to pull rocker shafts without rotating the crank?

[ThatM20Guy]

yeah that definitely sucks. Were you able to pull rocker shafts without rotating the crank?

The intake rocker shaft was flared out on both ends for some reason so in the process of getting it out I cracked the head. I basically just continued removing it for the purposes of me learning. Kinda sucks but I have newly machined head waiting for some love.


Sent from my iPhone using Tapatalk

[zaq123]

The intake rocker shaft was flared out on both ends for some reason so in the process of getting it out I cracked the head. I basically just continued removing it for the purposes of me learning. Kinda sucks but I have newly machined head waiting for some love.


Sent from my iPhone using Tapatalk

As you probably already figured out, rocker shaft should be removed by hand, with no rocker/valve spring pressure and without any hammering on it and screwing shit up along the way.
What I normally do: 1)remove rocker retainers from rockers that are not touching the cam. 2)slide those rockers to the side.3)rotate the cam and do the above for the remainder of rockers. Sometimes thick rope wrapped around the valve head while it's still open helps and gives you some extra breathing room.4)deburr the rocker shaft in the area where rocker retainers are sitting. Retainers scratch the shaft just enough to get stuck inside of rocker bushings and shaft journals in the head.

Once the above is done, rocker shaft will come out with a push of your fingers without messing anything up.

Did you pull that cam? wonder how it got stuck..

[digger]

I'd have though a issue with pump woukd torch rod bearings before anything else.

Are the rockers worn? If not then unlikely oil issues imho

[ThatM20Guy]

Did you pull that cam? wonder how it got stuck..

Had to go back to school so I didn't have time to pull the cam. When I get back I will try to remove it.

I'd have though a issue with pump woukd torch rod bearings before anything else.

Are the rockers worn? If not then unlikely oil issues imho

Didn't seem like any undo rocker wear from what I can remember, but I am going to rebuild it at this point so I will hopefully eventually find a problem.