Main Bearing and Water Jacket Gasket Failure!

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Hopkins
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Main Bearing and Water Jacket Gasket Failure!

Post by Hopkins »

Well! It's my time.

A couple of weeks ago I did my fortnightly run from London to Ipswich to collect my children for the weekend. I journeyed late so that the roads were empty and had a decent run, with the engine maintaining 5-5.5k for most of it. There did not appear to be any lack of power. However, on pulling up at the lights at the end of the A12, there was a horrible clanky, rattly vibration. At first, I wondered if something terrible had come lose in the drivetrain. There was also an aroma of things being a little too hot... I took the car to my final destination and planned to visit a garage in the morning.

In the morning there was no noise. The garage said that the exhaust or cat was very close to the heat shield and suggested that it may have made contact when hot.

On the way back to London that day, I noticed that the engine would cut out, in a manner which felt similar to fuel starvation, when the engine got much above 6k. Eek. This was a particularly bad time because I had my daughter's birthday treat at Longleat that weekend! So, I resolved to drive gently and keep my fingers crossed. On two or three occasions I confirmed that, yes, the engine was definitely objecting to revving much above 6k. Other than that, it still felt fine. Longleat was a success, followed by another return trip from London to Ipswich.

By coincidence, I had a service booked in a few days later with The Performance Shop, so the next time I took the car out it was to drive across London for an hour to get there. The car seemed fine except, again, with one final confirmation that it didn't want to get the revs up. I parked up early to await the opening time (it's so much nicer to miss the worst of the morning London traffic). On his arrival, I went through the symptoms with Rhys who began with better-case scenarios. However, when I turned the key in the ignition to move the car up onto the forecourt, plumes of blue smoke came out of the exhaust... Oh dear... It didn't take long for Rhys to diagnose a water jacket gasket failure, which would require a full rebuild. Later that day, I received a call saying that he could hear very clearly that the main bearing had gone. He thought it likely that the main bearing failure resulted in excess heat which was causing the cut-out and, later, the gasket failure. Given the chain of events, I felt relieved that the gasket failure occurred just after I arrived at the garage!

Looking back, I wonder whether this earlier post I made was the first indication that the main bearing might have been on its way out...

So! I will now treat my fantastic car to a full engine rebuild, and I look forward to making a few decisions along the way. I am hoping to receive some thoughts and advice from he wonderful folks on this forum. To start with, I have a number of questions!

1) What other components should I have replaced at the same time? Water and oil pumps, belts and thermostat have all been strongly recommended by TPS. They replaced all coils, ignition leads and spark plugs last year, so they should be fine.

2) Regardless of whether I get any porting, and in addition to any treatments in response to damage to the housings, are there any treatments to the housing which are recommended? "Reground housings" and "lapped irons" are two options listed by TPS.

3) Porting options are Street, Large Street, Half-bridge, Full-bridge. As entertaining as I find the noise of the bridge ports, this is my daily driver and so I have pretty much ruled that out. As far as I understand, the street ports are an option to improve torque in the lower rev ranges. According to TPS there would be some improvement immediately, but more improvement would be possible with a remap which would involve testing on a dyno.

4) As part of the porting process they said they'll round of the edges of the ports and smooth out the insides of the ports which are rough by default. I'm no fluid dynamicist, but I do know that smooth does not necessarily translate into lower fluid resistance. What are people's thoughts here?

5) I'm running a cat. I'm happy to run a cat and pay occasionally for a replacement. Admittedly, I'm running a cheap cat. Still, what are people's thoughts on porting with cats?

Any other thoughts would be much appreciated!
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by v-rex »

My thread on my rebuild with TPS, and there is also a link to a thread where we talk about rebuilding in general.

viewtopic.php?t=81823

I think it will answer your questions but a quick summary imo.

1. Yes all those sound good and I did that. Not 100% sure if I did belts, but did the rest. I also did coolant hoses as mine were shoddy but they would advise.

2. Definite vote on reground houses. I think it helps a lot with the result. Not sure about lapped irons.

3. I effectively have a large Street port and it's been perfect for daily driving. At high revs there's a boost in power that will use up a bit more mpg, but no real loss in mpg day to day. I've done 250-270 miles on a tank easy. One thing I should add is I tend to be a gear higher now after the rebuild, as the torque is there, unless of course I am having fun!

4. I had the same discussion on sharp ports and the full discussion is in the thread above. They smoothed out mine as well

5. CAT is no problem. I was running an ECP cat for my first service post rebuild and now have a racing beat cat and that also flew through the MOT without issue this year.

I hope that helps and it seems you have luck on your side, so I am sure you'll get a decent result. I love my TPS rebuild and the engine is so strong now. I've been going there since and they are great guys.

Feel free to ping me any Q's you have and I'll try my best to answer.

Vinod
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by PaulAV »

I would consider an oil pressure regulator upgrade to increase oil pressure to the bearings(same as R3) resurfaced housings are a good option(I had this service in my rebuild at Hurley's, the resurfacing work was carried out by garagereg on Mazda original machinery)
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v-rex (Mon Nov 29, 2021 5:52 pm)
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by 350matt »

Definitely resurface the housings and street port at a minimum - no need to lap the irons unless there's perceptible wear
I'd also consider a half bridge as that won't give you the funny idle and loss of low speed torque but does give more boost over 4500rpm

and yes do the re-map as this is worthwhile even on a stock engine
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by Hopkins »

Thanks for the replies. (And also the lengthy rebuild threads which I read all through!)

After some consideration and consultation, I've decided to leave the ports alone, besides the rounding off of the exhaust port to reduce carbon build up. The housings will be replaced with reground housings, and two of the irons will be replaced because the front rotor side-seals went - not the main bearing as originally suspected (although it was on its way out, apparently). Oil pump, hoses, water pump, thermometer will all be replaced, as will sparks. (Coils and leads were changed last year/10k miles ago.)

Apparently it will be ready by Christmas!

I'm also having the underbody treated with a weather resistant material, including up into bits not normally reachable when the engine is in place.

Exciting!
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ChrisHolmes (Wed Dec 08, 2021 1:48 pm)
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by Hopkins »

Time for an update! Firstly, he main bearing had not failed. Apparently it was "on its way out". The real culprit was a failed side seal of the front rotor. Then presumably overheating and ultimately the water jacket gasket failure. However, the noise suggesting that it was the main bearing I think was the noise described in this thread and it is still present but, finally, it appears to have been diagnosed!

The work was completed in the week before Christmas, and the TPS folks kindly met me there on the morning of Christmas Eve, just in time for a ridiculous amount of driving between London, Suffolk and Yorkshire over the festive period. TPS apply a 5k rev limiter until returned for a service after 850 miles. I took it to them yesterday at 1000 miles and I am happy to report that all is well! I have been advised to "take it easy for the first couple of hundred miles", but perform pulls up to the red line on slip roads. Apparently it is not uncommon to feel inconsistencies in power delivery in the short term while the engine continues to bed in, and while any accumulated deposits acquired during the first 1000 miles of crawling around have a chance to burn off. I did feel a little hesitation between 8 and 9k. Otherwise, the engine feels great.

A little sub-story: during the initial break in period, I visited Yorkshire - for a wedding! My clutch had been replaced too (apparently 26k miles on an Exedy Stage 1 is good), and I have decided to try out the Competition Clutch Stage 1 this time since it was £100 cheaper than the Exedy. However, half way from London I discovered that I couldn't get into first gear any more... Later, that "got better" but I couldn't get into reverse. Cue silly situations. However, by the time we returned to London I believed that the problem was that the clutch was not fully disengaging. This proved to be true, and it was because one of the brackets of the clutch pedal had snapped. In the absence of a replacement pedal yesterday, TPS welded it, and this seems to be fine, although they recommended a replacement at some point. Anyhow, I think I prefer the feel of the Competition Clutch Stage 1 to the Exedy. I wonder if it will last as long?

So, the RX-8 is back on the road. I have a trip up to Ipswich in just under a week and can't wait to stretch its legs on the A120. I cannot say that the engine feels particularly "tight", as others have described, but I'm looking forward to feeling any changes over the next few thousand miles. Then perhaps I'll find time to join you all for a track day in the second half of the year. Hurrah!
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njkmr (Sat Jan 08, 2022 6:39 pm) • ChrisHolmes (Sat Jan 08, 2022 6:56 pm) • hachiroku (Sun Jan 09, 2022 7:17 pm) • New Duke (Tue Jan 11, 2022 2:33 am) • v-rex (Thu Feb 17, 2022 6:00 am)
Hopkins
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by Hopkins »

Another 1000 miles in and the "hesitation" between RPMs of 8k and 9k may be diminishing. The experience is a sudden, albeit slight, decrease in torque somewhere between 8k and 8.5k as the tachometer reads. It is slight enough that I cannot notice it in first and second gear, but in third and particularly fourth it is noticeable. As well as reducing over time, it might be slowly moving up the rev-range too, but it is still obvious. I wonder if anyone here might have any idea as to what is causing it, physically?

From what I have read on this forum, it can take "a few thousand miles" for a rebuilt engine to bed in fully, so I'm disinclined to think that there is anything up with the engine which needs attention.
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by warpc0il »

It's clutching at straws but it might be worth checking that the two fine meshes inside the air intake ahead of the MAF are fully secured and in good condition.

Their job is to ensure a smooth airflow over the MAF sensor in all rpm/load conditions.

I have come across some very weird effects that loose/damage meshes can cause; anything from quite subtle flat spots to major "she's going to blow" symptoms.
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by v-rex »

Hi Hopkins,

Sorry after posting on this thread earlier I totally missed that you went for the rebuild with TPS in the end and only saw this now.

The torque dip is weird and I don't have anything to add really. You changed coils and sparks and everything so I am sure all is fine and as the engine was run at low revs for a bit during bed in it probably will open up and clear some of the higher valves ( which I believe is the VDI at around 7.5k ) and hopefully it will clear else I am sure Josh will get to the bottom of it if there are issues.

For me yes the engine was strong after the bed in but got even stronger a few thousand miles after. I didn't actually compression test or anything after but I remember after bed in there was some slight hesitation for a second or so on hot startups but now it just starts up straightaway, so the best is still yet to come.

Good luck and I look forward to hearing how you fare as you build the miles. My car did admirably at Silverstone and Snetterton so hopefully see you on a track before not too long!

Vinod
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Re: Main Bearing and Water Jacket Gasket Failure!

Post by Hopkins »

warpc0il wrote:
Wed Feb 16, 2022 11:59 pm
It's clutching at straws but it might be worth checking that the two fine meshes inside the air intake ahead of the MAF are fully secured and in good condition.

Their job is to ensure a smooth airflow over the MAF sensor in all rpm/load conditions.

I have come across some very weird effects that loose/damage meshes can cause; anything from quite subtle flat spots to major "she's going to blow" symptoms.
Thanks - I'll do that.
v-rex wrote:
Thu Feb 17, 2022 6:11 am
Good luck and I look forward to hearing how you fare as you build the miles. My car did admirably at Silverstone and Snetterton so hopefully see you on a track before not too long!
Thanks - I hope so too :).