Head gasket replacement and now knocking

[ZRotheohv]

A couple months ago I was at a friend's house, and when I tried to start my car to go home, there was a horrible grinding that turned out to be the starter. After towing it home and replacing that, it started wonderfully, except a nice plume of white smoke out of the tailpipe. A few tests later and it was obvious that the head gasket was toast, so I started gathering materials for it.

Fast forward to 2 days ago when I completed the whole job (including valve job/tipping and taking off .005" of the machined surface) and I was feeling pretty good about myself. The only problems were a code 26 off the check engine light and a lower oil pressure than I saw before the rebuild. It was about half way between the bottom line and the next line at idle, and at the second line at driving speeds. I also decided to run the timing 6 degrees BTDC instead of the factor 3 degree setting.

Now today I was driving up a hill with the pedal all the way down just to test it out, and it got to about 50 mph and wouldn't go any faster. Then at the top of the hill I could start hearing some kind of knocking sound so I let off of the throttle and the engine completely died. Luckily I could coast all the way down to the next red light where I successfully restarted it and drove the last 4 minutes home gingerly.

As soon as I got home I put it back to the factory 3 degree BTDC setting on the timing, but by then it was knocking regardless. I got worried about the oil pressure so I replaced the sender with a mechanical gauge, but I sat it on my bumper and when I started the engine, it fell off and broke! So real readings will be coming as soon I as get another.

It seems to knock a little at idle, then a little more when accelerating the engine, and not as much at a steady high rpm or when decelerating. I took a video and the sound seems pretty accurate. I have put so much work (and money!) into this car in the last month or so and I just want it to work!

Could it be detonation? Pre-ignition? A spun bearing? Rod knock? Maybe the oil pump decided to go? Are all of these issues related somehow? Are there any more tests I can do to help diagnose? Thanks in advance!

Here's a video:

 

[Jgrauman]

That's a rod my friend

 

[Michael Hanson]

Hi, Check compression, then a leak down test. Mike

 

[BILT4ME]

Have you had the power steering pump out for any reason?

Otherwise, start pulling plug wires on each cylinder progressively to see if the knock disappears. If it vanishes on a certain cylinder, then odds are it's a rod.

Good Luck!

 

[MoJ]

Is there any vibration/shudder along with it? Does it idle smoothly?

 

[elhombre]

Just want to second the diagnosis technique of pulling each plug wire to see if the knock gets much quieter.

A shot in the dark, but from your story, I would guess that the head gasket gave up and then filled a cylinder with coolant when you were at your friends. Then when you went to start it, the cylinder hydro-locked, and the starter motor was strong enough to bend the rod some, ultimately giving you the problem now. Just piss-poor luck. Hope we all all wrong....

I'm pretty sure most machinist end up taking off .010 when they deck a head while doing a valve job. Your guy got away with .005. With that little taken off, detonation is not a problem with our older engines. Pre-ignition usually is most prevalent when the engine is good and hot, and so is the outside temperature, under light throttle. None of which, you have going on here.

 

[slow95z]

Sounds like a rod man, sorry. I have long and short blocks that are un great shape I could hook you up with on the cheap.

 

[BILT4ME]

Just for the heck of it, check the exhaust. It may sound different, but it COULD be an exhaust leak either at the manifold or at the wye. A little tough to tell over the web.

Of course, I'm trying to help you deny (but actually troubleshoot to an undeniable state) that it's a rod knocking.......

Denial: It's not only a river in Egypt.....

 

[slow95z]

looked at the video again and i can see its a 93 or 94. i have 4 engines that would work for you ranging from 500 bucks to a grand plus shipping. i know thats not what you want to hear right now but if you go down that road keep me in mind.

 

[ZackR]

Let us know what the spark plug test reveals, it'll only take a few minutes to do.

 

[flintknapper]

That is not detonation (pinging). The job of the knock sensors is to attenuate that condition (fuel/air/timing) anyway.

That is most certainly a mechanical issue.

As suggested....pull the plugs one by one and see if you can isolate it to one cylinder.

Hydrolocked cylinder is a distinct possibility...but I would probably attribute it to an open injector (flooding the cylinder) rather than a headgasket issue (though both are possible).

 

[Pin_Head]

It is hard to tell, but sounds more like a ticking noise than a knock. Have you ruled out an exhaust leak? They get louder with more load on the ending. Rod knocks change tone revving up and down and will usually get quieter when you pull the plug wire.

 

[MoJ]

..but I would probably attribute it to an open injector

That’s what I was getting at with the question about shuddering etc. At least in my experience with a bad injector, the motor shook, lack of power, noise etc. Also multiple reports of folks buggering up an injector plug upon reassembly after a major repair

 

[Proven]

You can also use one of these and listen to the block along each cylinder.

https://www.amazon.com/Lisle-52500-Mechanics-Stethoscope/dp/B0002SQYSM

Touch all non-moving parts of the engine and listen for the sound to get louder.

 

[ZRotheohv]

I'll have to do a compression check (and leakdown) when I get back home from this weekend, but the last time I did it (before the head gasket blew), they were:

1-184
2-175
3-178
4-179
5-181
6-168

I haven't taken out the power steering pump yet, but it has been leaking for years and I was planning to do it soon. It is possible that I ran it out of fluid before, though.

I pulled the plug wires on each cylinder, but it seemed like the knock was the same no matter which one I pulled. I took a video but probably won't post it since it's embarrassing and shows me shocking myself and breaking my firewall heater valve and burning the crap out of my wrist... (what, is this my first day working on a car?) It just keeps getting worse! But it seems like it's independent of pulled spark plug wires. It does, however, have a weird growl when I open the throttle that wasn't there before this problem.

There is no vibration or shudder, either. It actually runs very smooth at all RPMs. There's just a knock! It's also pretty much independent of operating temp.

I also put a mechanical oil pressure gauge on there, and after it started up, it held about 10 psi at idle. Then I tried revving it up to 3000, and only got about 30 psi (minimum is 36). By the time I was done with these tests, though, the needle was against the stop at 2 psi (so I think it was more like 0!).

I put on the ol' stethoscope and started poking around the engine, and as far as I could tell, it's up front. The injectors are basically brand new and each one of them sounded like they were doing their job. I took the heat shields off and poked the block under each exhaust manifold, and it was loudest at #1 and quietest at #6.

What does a spun bearing sound like? Or a grenaded oil pump? Thanks for all the suggestions already!

 

[ajax1]

Did you ever have the crank loose

 

[ZRotheohv]

I've never loosened the crank... Could it have loosened itself somehow?

 

[BILT4ME]

I was asking about the PS pump because if it has been swapped and the gear damaged, it can make noises like this.

A "spun" bearing has a squeal typically. You don't have that.

However, you DO have low oil pressure and you have what sounds like rod knock, which is a LOOSE rod bearing that is hammering each time it goes up and down. Unhooking the spark plug wires stops that cylinder from firing and thus, stops that cylinder from hammering the rod on the crank with each rotation, it should be just "coasting" at that point.

Again, this could be an exhaust leak, also maybe a timing gear / chain tensioner / assembly issue.

If your harmonic balancer has NOT been torqued to 304 LB-Ft, then you may have weak oil pressure due to a poorly driven oil pump. That's why @ajax is asking the question.

Did you booger up your cam gears? Have a tensioner block in the wrong place?

Did you properly torque the cams into place? Maybe you have a broken cam or cam gear?

 

[flintknapper]

Any way something could have gotten on top of a piston?

 

[ZRotheohv]

If I drop the oil pan, would it be easy to see a loose rod bearing? Or anything else that's suspect? I was surprised to hear the knock occurring even though I removed each spark plug wire one by one. But I guess it's not conclusive that it's NOT rod knock.

But even if it was and I fixed it, I'd still have the problem with the low oil pressure. My first guess would be the oil pump, but is there anything else that could cause it (besides the crank bolt loosening itself somehow)? I tried to avoid getting anything in the oil galleries when I was cleaning the top of the block, but tiny particulate could have gotten in there. I'd think it would get caught in the oil filter though!

My cam gears were in pretty great shape when I installed them (and I did it exactly per the FSM), but I'll crack the valve cover open when I get home on Tuesday to be sure. I zip tied the cam sprocket to the chain while the head was off, and I thought it went back on correctly, but I'm second guessing everything now. How could the tensioner make a knocking noise like this?

When I buttoned the thing up, I took great care that nothing got on top of the piston, so I doubt it's something hopping around in there. As per the FSM, as soon as it went on, I put the spark plugs in, too, so I THINK I sealed it up pretty well...