A couple of weeks ago while driving across town, the engine very suddenly started making a loud tapping noise on the passenger side. Sounded like a diesel engine or, to me the amateur mechanic, a stuck lifter, loose rocker, etc.
Took it to the dealership, which happened to be close by, and they found that the valve cover gasket was blown, and the engine had leaked 2qt of oil over the last who-knows-how-long. I never noticed anything beyond a few drips on the garage floor; never thought much of it. Also, the oil pressure gauge never dropped from the middle of its sweep.
Anyway, they said that just putting in 2qt of oil made the noise go away, so they replaced the gasket, changed the oil, and called it done. As far as I am aware, they didn't actually inspect anything under the cover when they had it off.
Of course the noise didn't go away completely. It got much quieter and occasionally the noise disappeared entirely, but most of the time it was now a very quiet tapping. Just this last week, however, it got loud again.
Took it back, and to make a long story short, the mechanic said "this engine doesn't have lifters, it has 'pucks'. What it sounds like to me is that the aluminum 'pedestal' [his word] that the cam sits on has been damaged due to oil starvation."
He explained that the cam in this engine didn't sit in normal bearings, it had this aluminum pedestal thing instead, and it could have "grooves" worn into it in cases of oil starvation. But this is the good part about his message: "There is nothing to be gained by removing the valve cover and inspecting the [rockers, pucks, or whatever] is under there. Essentially, that head is ruined."
So my question for the experts: are there really NO serviceable parts under the valve cover that could cause a tapping noise after an oil starvation incident? My instinct is that maybe this "puck" thing (which the mechanic said "filled up" like a hyd. lifter) has siezed. Maybe after they put fresh oil in the engine, the puck "filled up" sometimes (which is why the noise did indeed disappear entirely a couple of times), but now it's well and truly siezed.
Do I really have no option besides "replace the head"?
The oil pressure gauge will always read about 1/2 way up if it has over 6psi of pressure. It is an idiot gauge.
It may have either gualled a valve or a lash adjuster. I would investigate further before condeming the head.
Thanks for the help. Those pictures made it crystal clear what the tech was talking about.
Here's a follow-up, which might be hard to answer: if my journal is damaged as shown in the pictures, would you expect a tapping noise synchronized with a single cylinder? I would think that if the damage were in the supporting structure of the cam, I'd get a racket pretty much every time lateral pressure was applied to a lobe, which is...multiply by 4...carry the 2... 4xRPM? Basically, I'd think there'd just be a constant noise (and, if the journal is getting little or no oil, things like smoke, buring oil smell, etc.). I dunno how many support points there are for the cam, so perhaps it's something like the middle support has been damaged, it's only rattling when one of the two middle cylinder's valves are opened, and no noise is made when end cylinder valves open, because the cam is still well-lubricated at the ends.
The fact that it's tapping at about 1/2 RPM leads me to believe that probably only a single valve is affected. Which gives me hope. Maybe false hope, but anything to save the cost of a new head. :-)
As soon as I get the truck back from the dealer, who I'm pretty convinced will no longer be much help to me (there is more to the story), I'll probably take it to an independent and ask them to please just pop the valve cover and take a look. Worth the $100-200.
P.S. I gotta add my cred line:
- 67 Mustang 289, all stock, 40K original
There are 5 cam supports.
Is there a miss in the engine? The reason I tore into that engine was because an intake valve had galled and wouldn't close completely. It only had 1 ticking as well.
But I still think that it is either a valve not completely closing (causing a gap between the cam follower and valve) or a sticking lash adjuster.
They aren't real hard to change.
Maybe, try changing the oil and substitute 1 quart of oil with a quart of ATF. The high detergent content of the ATF may free up a sticking lash adjuster.
The engine is running slighly more rough than I remember (a slight, occasional burble at idle), but it's hard to say for sure if this is truly a recent development. I think it's long past time to get the plugs replaced; possibly a contributing factor.
After getting it back from the shop the first time (after the gasket replacement and, of course, an oil change), I added a quart of a Justice Brothers additive (the type you can run in the engine, not the only-during-oil-change type), and the tapping noise got much louder the next day. I was thinking kinda like you said - maybe the detergent would free up whatever was stuck.
I believe the "oil flush" treatment that the dealer tried (yesterday) was also designed to clean things out with a detergent chemical.
I just gotta get a mechanic who won't BS me and will look under the dang valve cover, see what's going on. I'll be very pleased if it's a replaceable part.
Jimmy, what year was the Romeo exhaust valve problem? You know the one
2 qts down isn't THAT bad... Unless you were racing around corners, the oil level should have been high enough to keep pressure. I think.
If one cam journal was wiped out (and really out of round) it would leak enough oil pressure to starve the lash-adjusters. But generally, the entire head would be ticking, if that was the problem, as the pressure drop would be all across the head.
A cam journal knocking wouldn't be a "tick"
It'd be cool if the lash adjuster was bad... they aren't hard to replace.
Find another mechanic, tell them what you're going through, and just want someone to check it out. By taking off the valve cover and checking it - even checking the cam journals isn't too hard.