TAT TAT TAT TAT TAT [engine knock?]

[EMGEBE]

Hi guys,

The latest sook my car is having, is in the morning.
Im not very knowledgable about oil systems in cars, but when i start it up (cold), when it cranks over, there oil pressure gauge reads 0 for about 5 seconds...

TAT TAT TAT TAT TAT, then im guessing an oil pump gets its Doo Doo into gear, just lately its been very slow on startup.

Whats a good fix for this?
I've only just done a head gasket (2 in the past 19 months)

I DONT WANNA MAKE IT THREE! /ubbthreads/images/graemlins/nonod.gif

Cheers

Jarrod /ubbthreads/images/graemlins/thumbsup.gif

 

[Bugeye58]

Jarrod, look at my reply to your oil question.
Park it, the bearings have had it. The knocking you are hearing is the crank pounding on the bearings due to their being worn. The lag in oil pressure is from excessive bearing clearances, and having the oil pump work overtime to take up the slack.
If you keep running this way, it will make much louder, much more expensive, noises.
Jeff

 

[EMGEBE]

LOL!

FAN-F***ING-TASTIC

Ah geez i find the MG problems funny.

Is changing over the bearings an expensive fix?
-plz dont tell me they gotta lift the engine

I didnt think it was really a major problem, it just makes a bit of a tapping sound when i start up rather quickly. /ubbthreads/images/graemlins/rolleyes.gif

Cheers Jeff /ubbthreads/images/graemlins/thumbsup.gif

 

[Bruce74B]

I agree with Jeff...sounds like a nice winter project for you, Jerrod /ubbthreads/images/graemlins/pukeface.gif

Based on your oil pressure thread and this, I would recommend that you park her somewhere warm and pull the engine for a rebuild...unless you really want to replace the engine (v-6 or v-8 rebuild?) for much more money, I would rebuild it now before that TAT TAT TAT becomes a "GRIND GRIND GRIND-URRRRRRCCCCCCCH" and replace the bearings. This job will make your head job seem easy!

At least get your mechanic to give you an informed second opinion, but tell him up front that he won't be doing the job and see what he thinks.

Good luck, Mate! /ubbthreads/images/graemlins/cheers.gif

Bruce /ubbthreads/images/graemlins/driving.gif

 

[John Moore]

Jeff and Bruce are right. I had the same problem and the bearings were worn to copper. Personally, I would be very careful driving that car if at all. Your engine is telling you it's old, tired and need to be rebuilt. Maybe you can get away with putting in a new set of bearing, but probably the whole thing needs to be addressed.

Just beware, if you don't fix it, you will spin a bearing then you will be in a BIG mess.

But yeah, get your mechanic to give you a second opinion as Bruce suggested. But I'm betting you'll need to save those pennies for a engine rebuild.

 

[lawguy]

I've seen bearings seize, snapping a con rod, sending it out the side of the block....something you want to avoid.

 

[Guinn]

Hi Jarrod. I was going to come here and say that the combination of TAT_TAT_TAT and low oil pressure probably --almost surely-- indicates a worn out engine. As others have said, fix it before it really breaks irreparably!

I drove a bus for awhile and one day I heard a rapping. Half a mile further on it threw a rod right through the side of the block! No fun. /ubbthreads/images/graemlins/cryin.gif

Guinn

 

[EMGEBE]

hi guys, thanks for the replies, i just wanna clarrify something...
maybe u guys have me wrong here.

When i startup, the oil pressure is fine. NORMAL!
When i startup, the TAT TAT TAT sound is only present for about 3-6 seconds, (seems to be getting less lately), THEN ITS GONE

BYE BYE NOISE!

Are you really sure its a main bearing problem?

I've been reading around on the net, and alot of sources say its ok to have a oil pressure of around 15 or so, in hard conditions.

I just have a feeling its not as bad as u guys are making it out to be, ill get my mechanic to have a look at it.
see what he recons

 

[Guinn]

Hopefully the mechanic will say we are a bunch of worry-warts and find the source of your noise and low pressure, then fix it cheap! But I agree with you that someone should put hands on it before you decide to just tear it down and re-build.

Guinn

 

[John Moore]

Jarrod,

Your descriptions sounds exactly like mine, before I rebuilt my engine. Here's what mine would do. After the car sat all night and the engine was cool and all the oil in the sump, on first crank, I would hear a tapping sound or 'braapptt' sound at start up, then it would take a few seconds for the oil pressure to rise. I wouldn't get that for the rest of the day. Only at the first crank in the morning. My car did fine, the engine felt strong. But I got very low oil pressure at idle. I didn't want to believe it either, but everyone told me my rod bearings were going and if I didn't stop driving the car, I was going to spin a rod or put one through the block. Finally, I decided to pull the pan and check the rod bearings, and sure enough, they were worn to copper! It was the exact situation Jeff described above.

Maybe you can get away with just replacing the rod bearings. That's what I thought I would try, but when I got into the engine, I found it was just worn out. So I went for the full meal deal.

So do yourself a favor and park your MG, until you get it properly dianogosed. Hopefully it's nothing, but if your rod bearings are seriously worn, you could really do some damage to your engine.

 

[aeronca65t]

See.. the actual problem is that you're on the bottom of the world and all the oil in your engine is flying up to the valve cover.......no, I'm just kidding /ubbthreads/images/graemlins/jester.gif

But I'm with Jeff...park it.

And the problem is likely not main bearings....it's probably rod bearings.
15 lbs of oil pressure in a warm engine is enough for idle speed, but not for anything over 2000 RPM.
I realize that you probably won't do this work yourself, but let me outline what should be done by whoever does this work:
Pull the oil pan, remove one rod bearing cap at a time and inspect the crankshaft rod journals. Measure them with a micrometer and see if they are within spec. You may also wish to get some "Plasigage" (very inexpensive) and use it to measure the clearance from the rod bearing to the rod journal.
If you are very lucky, you may be able to put in new rod bearings (of the correct size) to "take up the slack". And this can be done with the engine in the car.
But normally, the crankshaft must be removed and reground or replaced (meaning that the engine will have to come out). And if the crankshaft comes out, you may as well renew lots of other parts while you're at it.

I just did this last week in my racer. I normally change my rod bearing every 20 hours or so, but I had let these one go just a bit too long. It was "TAT-TAT ing" for about 100 yards before I shut it down and had it towed in. You can see in the picture below that the left side bearing was hammered so hard it "squished" out of the rod cap like toothpaste.

My crankshaft has already been ground down three times before, so I needed a new crakshaft.
My repair costs (with no labor..I did it myself) were about $1000 American. I have no idea how much that is in Oz dollars but I'd guess that it's enough to buy a truckload of Foster's or so.
G'luck!

 

[Dozuki]

Hi Jarrod, (and everyone else, my first post)

The above post is good advice. I doubt that your bearing is squished out the cap as that is extreem, but hi is a racer =)

I've lost one spit engine years ago to a bad bearing and thrown rod through the block. It's a distictive sound (bad bearing), and once you hear it you are likley not to forget it. I lost another bearing in another car a few years later and was lucky enough to catch it in time because I knew right away what it was.

It's really not that hard to pull the pan and check the rod bearings. It's pretty obvious when one is bad by looking at them. If you do have one bad, replace them (all the rod bearings). Run the car gingerly for a bit and if any sign of the bad bearing comes back, park it and rebuild. If it comes back then you have a flat spot or some other aberation on the crank and the engine needs to come out.

I only say this as it seems you are reluctant about the problem and don't really want to pull the engine. I'm going to do this same check shortly on a B I just bought to see how the internals look. Definately use Plastiguage, only a couple bucks and simple to use. New bearings should be fairly cheap too.

-D

 

[BradHollister]

I'd do what D said. 1/4" Rachet, extension, 7/16 socket, socket, tourqe wrench, socket for rod bolts, jack, stands, some oil, gaskets n' sealer. 2 hours for the inexperienced...bingo, bango! Done!

Brad

 

[BradHollister]

P.S. And a little endurance in the arms...