Author Topic: 5 Reasons for engine failures on RX7\'s  (Read 2544 times)

Offline chris

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5 Reasons for engine failures on RX7\'s
« on: March 30, 2005, 06:49:26 PM »
After reading Boomins post about the 50k rebuild claim I thought it was worth clearing up a few issues.

I can give first hand knowledge of engine life; I worked as a Mazda technician from 1991-1998,  where I fitted many engines under warranty and rebuilt several for customers on UK fd\'s long before people started importing Rx7\'s and years before any Fd\'s were seen outside of the Mazda dealership network, from 1998 to 2001 worked part time at RX Motors where I have examined hundreds of blown FC and FD engines and from 2001 to date have been rebuilding engines for my own customers. During this time I do not believe that I have seen more 13b turbo cars than I can count on one hand that have allegedly made the 100k miles mark, and some of those I think were rebuilt/replaced prior to that point.
In general most FD\'s are doing well if the engine is untouched at 60k miles, and does indicate more motorway mileage.

Hopefully this will help answer the expensive \'what happened to my engine\' question

In the early days the need for rebuilds was mainly due to seal failure on circa 60k miles, however as we started reaching the 8-10 year old phase of most of the fd\'s out there, it is more common to be due to either water seal failure or water channels cracking, there are several reasons as I see it for different cars obtaining different mileages and reasons for failures:

1/ Tip failure due to wear, this can differ from car to car depending on the type of driving, long motorway journeys vs. short stop starts (multiple heat cycles from hot to cold)

2/ Tip failure due to detonation, more common on modified cars but not unheard of on poorly maintained stock cars (plug/lead failure, fuel system problems etc etc)

3/ Water seal failure, as Carl says in boomins post, degradation can be hugely advanced due to leaving a flooded engine full of fuel, which attacks the seals. There is also definitely a connection to corrosive antifreeze attacking the metal surrounding the seals, and general degradation of ten year old seals, again effected by multiple heat cycles and aging cooling systems (poor water flow through rad, water pump cavitation, lack of ducting etc etc)

4/ Water channel failure (cracked plate around the seal channel) this seems to be due to difference of thickness of material around the outer edge of the seal channel, the thickness varies considerably, this is compounded when corrosion sets in and attacks the already thin metal, causing a fracture point. (This is again not helped by poor water flow etc)

5/ Warped plate/plates and shrunk housings, this is primarily due to severe overheating due to prolonged driving once overheating has occurred (due to lack of water, as in a leak, poor water circulation or a fault as listed in 3 and 4)



Sorry it is a long post but hopefully clears up a few issues

Offline davefrith

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5 Reasons for engine failures on RX7\'s
« Reply #1 on: March 30, 2005, 09:41:05 PM »
interesting reading

Offline gsb876

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5 Reasons for engine failures on RX7\'s
« Reply #2 on: March 30, 2005, 11:49:56 PM »
Thanks for that Chris appreciated buddy.
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PETE SMITH

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5 Reasons for engine failures on RX7\'s
« Reply #3 on: March 31, 2005, 12:21:16 AM »
I believe my recent second tip failiure was due to, perhaps, a mix of points 1) and 2).Well presented Chris..Do you remember fitting my Apexi FMIC in Bournemouth, all those years ago?!:)
Pete

MattyGTI-R

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5 Reasons for engine failures on RX7\'s
« Reply #4 on: March 31, 2005, 12:26:01 AM »
very interesting reading

Offline gsb876

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5 Reasons for engine failures on RX7\'s
« Reply #5 on: March 31, 2005, 01:00:07 AM »
Can i ask, which is worse driving the car everyday, or only driving the car at weekends ???
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Offline Dan Norton

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5 Reasons for engine failures on RX7\'s
« Reply #6 on: March 31, 2005, 01:39:16 AM »
Quote
Originally posted by gsb876
Can i ask, which is worse driving the car everyday, or only driving the car at weekends ???


Iwas thinking the same but maybe,depends on what kind of driving you do tho gurj?

Say you do a dual carrigeway run to work for 30 mins everyday, compared to short stop start runs at the weekend?

Different situations and all that.

Dan!!
Turned into the worst part of my life....my precious fd3 has gone, but never forgotten....roll on a new life!!!!

Offline gsb876

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5 Reasons for engine failures on RX7\'s
« Reply #7 on: March 31, 2005, 01:45:59 AM »
Chris here has the knowledge to answer this question unbiased so would like to know just for myself really.

As usually peeps say driving everyday is not good for the rx, however being stood still for ages isn\'t either, so which is better ??? :confused:
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Offline Dan Norton

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5 Reasons for engine failures on RX7\'s
« Reply #8 on: March 31, 2005, 01:50:40 AM »
I know what you mean mate.....i\'m unsure aswell....just thought i would put the differant scenarios across.
Turned into the worst part of my life....my precious fd3 has gone, but never forgotten....roll on a new life!!!!

Offline gsb876

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5 Reasons for engine failures on RX7\'s
« Reply #9 on: March 31, 2005, 01:54:34 AM »
I use my car most days, but allow for decent warm up / cool down sessions, and car is not driven hard everyday.

Usually wont go over 3500rpm in everyday driving, once a week give it a blast to clear out the carbon build up.

Most of my mods are to deal with reliability mostly, so hoping i am doing the right thing ??
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Offline chrisBoid

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5 Reasons for engine failures on RX7\'s
« Reply #10 on: March 31, 2005, 08:42:15 AM »
Somebody with the power, make this thread sticky!

I don\'t use my car that often.

* Maybe once per week for a couple of short 7 mile runs where I don\'t go above 2750rpm.
* If the weather is not terrible and I have the time I might go for a blast at the weekend of about 40-50 miles where the carbon is cleared out.
* Perhaps once every 3-4 months I\'ll do a journey of 100 miles+.

My original engine has only done 31,000 miles and it\'s a \'96 model.  I keep a trickle charger on it to try and elimiate the possibility of flooding (it\'s worked so far).

I am accutely aware of point 1, and I hate using my car for short journeys; I always sit for at least a couple of minutes at trhe end of a journey with the rad fans going but my engine bay still remains quite hot :(  I should invest in one of those great big fans they use for rolling roads :)

Top_gear_towers

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5 Reasons for engine failures on RX7\'s
« Reply #11 on: March 31, 2005, 11:42:21 AM »
trickle charge?

Should I be charging the car all week? (I only use it at weekends).

Offline chrisBoid

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5 Reasons for engine failures on RX7\'s
« Reply #12 on: March 31, 2005, 11:53:08 AM »
A trickle charger; plugged into the mains and connected to the battery, I use one because I may not drive the car for 3 weeks.

Plus I had problems with my battery running down if I didn\'t use the car for 2 weeks.  I attribute it to the tracker unit that is always on because it sends SMS\'s when various things get triggered.  I did complain about this to the manufacturer who replaced the unit which is now supposed to have a more economical power consumption.

petemillis

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5 Reasons for engine failures on RX7\'s
« Reply #13 on: March 31, 2005, 12:29:05 PM »
I\'ll drive the RX7s at least 2 to 3 times per week. If I need to move one a few feet I\'ll push it.

When I start up I just let the engine rev stabilise before driving off, and keep the engine speed between 2500 and 3500 rpm using 1st and 2nd gears for the first few minutes. This allows the engine to warm up quicker than leaving the car sitting there ticking over, and also ensure that the engine isn\'t being laboured at all which is one of the worst things to do.

If you think about an engine being laboured when it\'s cold, it puts far more strain on the all of the internals than it does by keeping the engine running at a decent speed (like 2500 to 3500 rpm).

This extra strain is also applied to things like the apex seals as a lot more forces is required to move the car along at low engine speeds. Also, by labouring the engine you\'re far more likely to get the onset of pre-ignition.

If you just run the engine really slow, or let it idle for too long, on start up then you end up burning a really rich mixture which equals carbon build up. Once carbon is there, it\'s there - you can\'t just blast it out with a long fast blat. It bakes onto the engine components and seals and that\'s it. Surely the best way is to minimise carbon build up in the first place by reducing the amount of time you have it running rich.

I\'ve got a lot of experience with 2 stroke off-road enduro race bikes. And the thing they really hate, and that causes loads of carbon build up, plug fouling and knackered piston rings is being left idling for too long warming up and then being laboured rather than letting the engine run freely. Also, I always run the bikes (both pre-mix and oil injection bikes) with low smoke, low deposit synthetic oil - and never see any carbon build up. Modern mineral oils are also good in this respect but aren\'t so stab;e at high temperatures. I know that minerals are what the majority of people recomend but I do like low smoke and low deposit synthetics (and they won\'t gum up apex seals - when I rund them in 2 stroke motors the piston rings and ports remain virtually spotless)

Offline chrisBoid

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5 Reasons for engine failures on RX7\'s
« Reply #14 on: March 31, 2005, 12:37:36 PM »
Yep, I always preferred to get on the move to warm up, now I have a factual reason for doing so apart from the noise pollution, thanks Pete :)