My Mars Red Mk1 - Thread REBOOT- P82

Hope you get it all sorted and so nice to see everyone helping out.

 

I had a Mazda 323 4x4 Turbo which had the same engine as the MX5`s, crank sheared and the pulley fell off ! wrecked the engine , luckily under warranty

 

Fair play to you and all your helpers pulling together to sort you out, shame a minor component failure stopped you getting more runs at Curby. Im sure it will be sorted soon and even better ! Good to catch up for a chat though

 

Common problem with those Mazda lumps, from what I hear... 'common' problem for what is a pretty reliable car.

 

Agree, new parts to be fitted, then torque and check.
Glad it was caught just in time!

 

Drill and dowel pin? Easy and safe!?

 

Gurd's...bad luck, but your not alone with crank pulley issues, just had a brand new one fail myself, and seen it on a few 2ltr 16v's now. Apparently it's fairly common on 2ltr 16v's when rev'd hard to throw off crank pulley's...doesn't appear to be an issue on 1800 16v based engines, and I've never had an issue with high (9k) revving 8v's.

The other issues are clutch's/flywheels falling off when the bolts work loose and wreck the back of the crank (ask me how I know that one too!) and P/S & alternator bracket fractures...a harmonics issue with 2ltr 16v's perhaps.

I have a solution tho...1800/1900 based 16v's!...revs "with" reliability!

The nose of your crank will need squaring up on the face or you'll have the same issue again. There is also a grey area over the torque setting...90NM is around 65 Ib/ft, + 1/4 turn? which I'm told would be around 120 ib/ft....bloody tight but some listings show 90 NM, 90 degree's "+" 90 degree's again!...there is also a 146 ib/ft setting...I did the last one to 150 ib/ft plus an extra "heeeve"!...160-170ib/ft...with the bolt threads oiled and ARP lube around the coller/in-built washer...so far so good apparently.

Same for the pressure plate to crank bolts...use ARP bolts torqued to 70ib/ft...std bolts @ 55-60 arnt enough at higher rpm.

I know of another engine builder who used to do some VW cup 2ltr 16v's...they used to throw clutch's off too! He drilled them with extra dowls but they still worked loose...tho with 4 zero's on the tell tale it may have been a different issue in his customers case!

 

Jason ... are you referring to the ABF based 2.0l and / or 6A & 9A ?

 

The concern was not the pulley though. It was the cog/gear tha, even though it was thought to be tight.
This was discovered when I took it apart, as explained higher up and a temp fix was attempted but the damage to the cog and nose was already done.
As the cog was slack it would beat itself into and oval, shear the locator, batter the key way and damage the nose as in the picture.

It was believed the engine was like this with the previous owner, who from my experience with them 4 years ago, had problems with performance on this same engine.
Back then it was the **** dyno and I was a bit puzzled why I could not get the engine to perform as expected...know I know lol
The picture that was taken, shows the thrust side of the key way batterd a bit and the nose with the ridge that will need squaring up as you said.
So new parts have been bought and the nose will be dressed up before assembley.

You are right about the final torque on the crank bolt. When we develop OE engines in a climatic chamber, we have to attach a hub, mounted to the damper, called a "JODAN" for independant engine position. The OE crank bolt is also ~90Nm + a 1/2 turn. I remember asking the technician to show me the final torque, after this procedure and it was over 200Nm.
Also most issues like these, including cam gear key way breakage seem to occur on factory ABF engines and not 1.8 KR motors. This is what I have seen back in the day. I do not think hi rpm is a concern though as these were just road vehicles, with OE 6900 rev limits and driven between 1-4k rpm.

So what caused this problem? In hindsight, we believe crankshaft bolt was not simply not clamping properly from way back when Dils owner the engine and not helped by our rigourous testing the last few nights.

Once clamped properly, our RPM limits should not be a concern. Thanks for everyone's input though

A permanent fix is already on the way.

 

Sorry for the lack of response from me. Been busy earning back lost brownie points with the family

Thanks for all the help and support guys. All your comments are read through in detail and information taken onboard.

As there is no washer available for this engine, that options out. I'm not modding one to fit.

The fact that these fail on stock engines leads me to believe it's due to an incorrect reassmbley or tampering at some stage during engine life causes a failure. Jason, you have seen a brand new one fail is worrying but from a far from stock engine I guess? They are known to fail quite readily on the G60 and diesel engines but this had been put down to the extra strain of running a supercharger/diesel pumps off the crank pulley system. Later diesel engines ('98->) from VAG came with a clutched crank pulley which would take the rapid accel/decel off the crank pulley and thus bolt too. Not 100% this is the true reason why VAG did this.

Pinning the sprocket seems like a good idea as it would stop the sprocket from wanting to turn about the face of the crank but again, this movement could only occur if the bolt clamping force was already failing. Seems to me the real fix for this problem is just to be brutal with torque procedure and really make sure that sprocket is fully clamped. I may still employ the pin technique but still on the bench about it. I would use a proper dowel pin and NOT the end of a drill bit like I've seen lol.

I'll report back on the condition of the end of the crank nose and go from there. It really wouldn't be worth taking the cran out of this 150k mile engine. In any case, I have secured a deal on a very low mileage lump from a fellow enthusiast as a spare too.

Gurds

 

Both...mine and the other engine builder's were ABF based, but I've heard of 9A's with the same issues, and in fact saved one (9A) on the dyno when I saw the pulley wobbling

 

Thank you ... I`ll check my 9A then, prior to and when it runs - built 80 miles but six years ago ... long story !

A previous 9A ran to 7800rpm, never checked the pulley and still OK with `new` owner, did stretch the flywheel bolts though.

 

Eddie, by pulley I do in fact mean the cam/crank drive pulley as opposed to the outer pulley...not seen a failure on one of those yet.

Gurds, yeah a bit over stock...by 100hp...but yes brand spanking new...for the very reason I knew they failed and did'nt want there to be an issue. I do wonder though at the quality...would VW be having them made on the cheap now they're way out of production?

But either way, it looks more and more like a harmonics issue if it's common on other long stroke VW's (diesel), the pump/charger drive issue is interesting as I was thinking a similar thing with the chain of the inlet cam off the exhaust. Some appear to last the course but others obviously fail. Does'nt appear to be an issue with high rpm 8v's either...another pointer to the auxillary drive issue perhaps with the 8v only havin the one cam.

Either way, limiting the rpm maybe ok, but I wont be doing any big rpm 2ltr 16v's again on the std stroke crank...not when more than enough power can be had from less capacity with no issues...CC is'nt everything the yanks will have us believe! lol

 

There you go...bloody 2ltr's!

 

Thought you mean the crank cog/drive.

The damper does fail, when the rubber breaks up. I have seen a few of these failures.

Harmonics could be concern with respect to the valvetrain with agressive cams at high engine speed, but then I have seem more engines without a problem than those with.
The engines with concerns, some crank cog and others cam drive, have been in MK3 16v vehicles driven like Miss Daisy! Makes you wonder about past service history as is the case here.
As you said, peharps a change in supplier of the crank/cam drives on the MK3 16v (possible if there would have been a cost save) or the 10.8mm lift and cam profiles on the 051 101/101A/102 cams may have something to do with it.

I still maintain though, if it is fitted on a square crank nose and torqued up properly there should be no problems.

Still lessons have been learnt!

 

I'm told they used to change the clutch and flywheel bolts on John Morris's BTCC cars between quali and the race, because otherwise they tended to fail.

I've also seen some bottom ends where the crank pulley was dowel pinned to the nose of the crank - little thin dowels because there's not much room in there. I guess if they were a close fit it could stop the pulley from fretting at the keyway if the bolt stretches. Might not stop it wearing completely, but could slow it down a lot.

 

Would dynamically balancing the bottom end help?

 

Not if the cog/drive was slack

 

I was thinking more about the engines that let go with new bits, good Pastor!

 

+1. Well done Cgti , putting the Club name to its proper use.