[downest]

Ok so my sister's car (93 MX-6 V6) started making a nasty rapping noise last week. It's been sitting waiting for me to fix it for about a week and a half. So I start it up and listen, rapping, but it doesn't get louder when I rev it, it seems to get faster but drowned out by the motor noise, which isn't much. I always thought rod knock would get louder with the motor revving. It happened while she was driving home from NY, she said it felt like she lost power and it started making noise. She pulled over and waited for my dad, who then followed her home another 10 or 15 miles, and she said it didn't always rap, but always felt wrong. I was thinking it could be the hydraulic lifters, they may have air in them, allowing then to compress and not open valves correctly, but I don't know if it would be this loud. I'd like to get a second opinion before I pull one of the valve covers, since it's a royal pain in the ass on this FWD V6, I have to pull out the huge manifold first.
The engine was rebuilt a few thousand miles ago, during the winter, by me and a friend, so the bearings should be new, but I didn't do anything with the tappets since I didn't really know anything about them. It's been running fine since then.

 

[FooFighter]

LOL the only thing I can think of that sounded like that is when I seized a cylinder on my Hyundai Excel... I tells yea once that sucka was seized you could hear me coming from 7 blocks away(not even joking ...)
One thing that surprised me was I was able to keep driving it with only 3 working cylinders for about 2 months before she finally gave up and dyed…
However for those 2 months I was getting 8km per liter, and went through 1 liter of oil per week!!!
So I think it was good that it dyed because it used more oil and gas than a hummer!

 

[downest]

It's not that loud, you can't even notice the noise above 3000 RPM. It also sounds like it's coming from the head more than the bottom end, but it's hard to tell 100% without a stethoscope.

 

[CrxCarl]

Ask Ollie, he would know because he is a Ford mechanic and that is basically a Ford motor.

 

[downest]

Thanks dude, I didn't know Ollie is a Ford tech.

 

[SETI20]

Ticking valves sound somewhat like marbles on tiles. Can't really make a guess regarding an engine I don't know.

 

[ollie]

Hmm......i would start by using an engine stethoscope Tom.
That way you can get a good approximate for the source of the noise.
I would agree with Seti,bad valvetrain sounds like marbles on tile.Also the noise would get noticeably louder on accel.
So its a knock or more of a tick?

 

[downest]

It's a knock but it seems to disappear at mid to high RPM. I know what valves out of adjustment sound like, more of a tick than this, but I also messed up adjusting mine once and my car sounded like a lawnmower!

I've pinpointed it to the rear head, cylinder closest to the timing belt/passenger side. I really do not want to get in there, I have to remove the PITA intake manifold, and I don't know what I'll do when I do get it open.

 

[ollie]

Well amigo if it seems to resonate from under the valve cover it is most likely valvetrain related sir.
...Hmm..On another note...now dont shoot me,but its been a long time since I've seen one of those apart.What was the condition of the timing belt and tensioners? Maybe related?

 

[downest]

Rebuilt this winter, new belt, new hydro tensioner. The old tensioner failed after we did the water pump, and the belt tracked off and shredded.

 

[zerocool1014a]

how bad did it loose power? a friend of mine had a mx6 that was making tapping noises alot like what you are talking about and it ended up being timing belt related.. and actually some dumbass when they replaced the timing belt had left some small pieces of the old timing belt in the cover..well long story short we were coming back from running a canyon and all of a sudden his car drops in rpms and couldnt drive more than maybe 5mph... his timing belt jumped 2 teeth... the car never ran right again.. he replaced the engine and not even two months later the transmission went out. but yeah i hate to be redundant but it sounds to me like valve/timing issue

 

[downest]

Yeah someone on the MX6 forum (honestly not nearly as good even as the guys on HT) said the tensioner is prone to coming loose and slapping the engine, and then letting it skip teeth. I am trying to convince my sister to get a teg, she likes the way they look, and I know she would be better off.

Canyon running an MX6!? Dude you're crazy, even with Illuminas and springs, poly bushings, larger rear sway and good tires this thing understeers like you read about! Not to mention working the damn power steering in a quick corner can break your wrist!

 

[zerocool1014a]

yeah well i wasnt driving it, i was driving a 93 toyota paseo the car i had before my rex, and im much happier with my rex. also yeah i would push the integ, i personally dont like ford/mazda (except the rx7) the build quality just doesnt seem to be there.. who wants a sports car that is breaking down all the time and costing a ton of money after the initial purchase price

 

[downest]

Here's a new one...
I pulled the rear valve cover, and the exhaust cam sheared in 2.

Go Mazda.

 

[downest]

Here's a pic.

My mother rocks a K series and my sister breaks cams.

 

[Tiersin]

One more reason to love my honda. It dosnt break cams. How did that happen exactly? did it happen when you were taking it out or was that the cause?

 

[downest]

It was like that in there, it was rapping because the sprocket side could move left and right. I don't have any good explaination for it, must have been a casting defect or something.

 

[ollie]

Well then I guess we dont need any more speculation as to the source of the noise do we? :shock:
GL on the fix Tom.

 

[zerocool1014a]

just gotta say wow.. and that sucks, good luck on getting it back on the road. i personally like those cars but have never been around one that hasnt had problem after problem after problem..

 

[downest]

It was an easy fix, grabbed a new one from the yard for 20 bucks, and got it back on the road in under an hour. I'm a little worried about filings from the ends grinding against each other floating around in the motor though... we'll see what happens. I want to get rid of that car and get her a DA.