I have a 1988 RX7 GXL stock S4 NA engine. I kept hearing a noise which I thought was the clutch release bearing because you only heard it when you pressed the clutch pedal. Anyway to make a long story short the noise is actually coming from the front of the engine (I believe from the oil pump chain) because the eccentric shaft has like a 1/4inch of endplay. I didn't measure it but I'd guess it's about that much. When you press the clutch pedal it actually moves the whole eccentric shaft forward in the engine. Just wondering if anyone has ever seen this before and what may have caused this. The engine is a fairly new mazda rebuild with roughly 40 or 50k on it. It still makes good power and compression so I plan on tearing it apart and rebuilding it if it is possible. I'm fairly new to the rotary world so I'm still learning about these things. Any advice would be greatly appreciated. Thanks.

Bryon

 

If I understand what you mean by endplay, the only way your going to get a ¼ inch play is if someone had the front cover off and messed up the thrust bearings when it was reinstalled. If it only has 40-50k on it i would pull the front cover and take a look at the bearing/oil pump drive and spacer stack, check for damage. Anymore history on the engine?

 

I bought the car from a friend of mine who installed the engine and he said he bought the engine from Mazda. Other than that I don't know too much about it. I've only owned the car for about a year and a half. It only started to make noise this spring. I was thinking the same thing that there might be a problem with the thrust washers and spacers that they have in there but you would think that it would have made noise right from day one. It didn't make any noise last summer just this summer, and it got progressively worse as the summer went on. So you would almost think that something inside is wearing and creating more and more play.

 

You would only be guessing at this point, what you discribe is defiantly not rite. You need to look inside to see whats going on.

 

I plan on taking the engine out and tearing it apart just to make sure nothing is damaged. I did drive it all summer like that so who knows by now what kind of damage has been down. Like i said though it still runs awesome so hopefully it won't need too much work

 

Whoa,1/4" ? Thats alot of endplay....

Before you tear the whole engine apart, I'd pull the front cover off first to see if anything is wrong under there.
With a 1/4" of endplay I would imagine everytime you press in the clutch you'd be changing your ignition timing too. The helical cut gear that drives the CAS would move forward and actually change the ignition timing between shifts lol, thats crazy.

 

Yea it's pretty crazy and I don't doubt that the ignition timing was changing. When I tear it apart I'm almost expecting to see major carnage to the CAS gear and that oil pump chain cause after all it's had about 10,000kms put on it since it started making noise. It really shows though how tough these engines are cause it still drives awesome and was still taking abuse from my right foot up until about 3 weeks ago when I took it off the road.

 

I'm gonna measure the endplay with a dial indicator and maybe take a video of it running before I take it apart just so everyone can see this.

 

Is the front eccentric shaft bolt torqued to spec?

 

The bolt is tight, and the pulley does move about 1/4" when you yank on it, it's nothing I have ever ween before, maybe they left the needle bearings, or the spacer out I don't know.

 

My bet is they left the spacer out too...

 

my guess.
the front bolt was over torqued and the end play was to tight.
being run like this the torrington bearings would fail and fall apart.
run a little longer the cages that hold the torrington bearings together
get ground down, once they are worn away that will leave about 1/4 inch play.
I am guessing that is what you will find once the front cover is removed.
you may not need to rebuild the whole motor but a close check of the oil pump
clearance will be needed as well as cleaning out the oil pan.
my 2 cents.
Matt

 

You might be on to something with that theory cause that would make sense. If I get some time this weekend I may try and pull that front cover off. It's a really easy job considring I have a Koyo rad and an e fan on it. You can get at the front of the engine really easy.

 

dont forget the oil pan bolts, the ones around the front have to come out to.
matt

 

Yeah and they are the worst, the steering rack is right in the way. You might want to lift the engine up an inch or two just to get a socket on the oil pan bolts.

 

Good to know. I work on the worst vehicles the automotive world has to offer everyday so I'm sure I'll be able to get it apart. I'm pretty crafty with flex sockets and rachet wrenches.

 

Ok, I'll bite. What is/are the worst vehicles to work on?

 

Torque on the front bolt has nothing to do with end play. If you're able to change end play by manipulating torque on the front bolt, you've assembled the bearings, thrust plate, and spacer in the wrong order.

 

I'm an apprentice mechanic at a local independantly owned shop so I see it all and pretty much hate it all. I especially hate Pontiac Montana/Chevy Venture vans and any car that Chrysler built from about 1993 to 2004.

 

The engine may have been assembled with the wrong thickness thrust spacer and caused the end play to be too tight. That would create the same effect over time. I'm planning on tearing into it tonight and I'll bring my camera with me.

 

either the needle bearings and spacers arent there

or this....

(when u dont put the bearings together properly and pinch n run for 20,000kms hahaha)

 

WRONG
try it before you talk!
all pre 93 motors need to be torqued to the mazda spec. 80 - 98 ftlbs
the 93 up are torqued higher and are less sensitive.
but with the older motors the higher you go the less end play you will have.

again I say TRY IT !
torque the front bolt to mazda specs check end play.
then try torqueing to 150 and check end play you will find that it will be less.
I don't know if its crushing the spacer or if its distorting the rear race
but you will find the end play is reduced by torque!

been there done that.
Matt

 

So you're telling me to over torque the front bolt to 150 ft. lbs, which is 70 - 52 ft. lbs OVER the Mazda specification of 80-98 ft. lbs (for 1st gens its actually 72-87ft. lbs), and then be surprised that the end play has been reduced? Are you serious?

Here's a question for you... what's special about that thrust washer that differs between 13B and 20B engines?

 

I am serious, I have seen this more than once!

as for your question, depends on the years.
I will have to go out the the garage and look i guess.
I happen to have a 20b apart on my bench as well as a 13b rew
and a 13b t . along with a storage container with many 13b 6 ports some old 13b 4 ports..
matt

 

ok I looked in the fsm to be sure that we were talking about the
same part "thrust washer" what I would call the outer torrington race.
my answer stands.
depends on the year of the 13b you are comparing the 20b to.
if by 13b you mean all the "older" 13b's the 20b is bigger
If by 13b you include the 13b rew they are the same.
if there is some difference that would require a micrometer to see
well so be it, looking at the 2 parts side by side they are the same.
now something that does look a little different on the 20b was the thrust
plate the 20b one appears to be a little less tapered.

next question
Matt