Bongo Fury

Thanks, Steve.

Fixed link...
http://lushprojects.com/bongopartsmk2/c ... no=.html#7

Not a through hole, eh? That would have been too good to be true!

briwy wrote:It was just with Matt saying that it bolted into alloy that made me think it might just be a plug Steve. Is it the same as the other head bolts that come with a new set?

Must admit it looks more like a head bolt, not sure it why it would be letting oil out though if that's the case. I agree if it goes into the block its likely a helicoil is the only option but might still mean the head off I guess.

Sorry briwy - didn't reply to this one.
The bolt in question (one of the 'A' bolts) is smaller than the head bolts.
The 18 head bolts (12mm dia) are stretch bolts, whereas the 2 'A' bolts (less than 10mm dia) aren't stretch bolts.

What I have been asking myself is why the thread has stripped, and the only reason I can come up with is not what we want to hear. Let me run it by you:

The actual head bolts are tightened to 29Nm, and then through an extra 2x90 degrees (Mazda spec). ie- bloody tight.
However, the two 'A' bolts should only be tightened to 19Nm. (again, Mazda spec)

If the guy who tightened them took them to 29Nm, then they are over-tight, especially when you consider that they bolt into an alloy casting. This would have caused the stripped thread. (18 Head bolts are screwed into the stronger block material)
What would concern me is that BOTH the 'A' bolts could be stripped. Wonder if he has checked that the other 'A' bolt is loose?????

widdowson2008 wrote:What I have been asking myself is why the thread has stripped, and the only reason I can come up with is not what we want to hear. Let me run it by you:

The actual head bolts are tightened to 29Nm, and then through an extra 2x90 degrees (Mazda spec). ie- bloody tight.
However, the two 'A' bolts should only be tightened to 19Nm. (again, Mazda spec)

If the guy who tightened them took them to 29Nm, then they are over-tight, especially when you consider that they bolt into an alloy casting. This would have caused the stripped thread. (18 Head bolts are screwed into the stronger block material)

Highly likely. The head is spotless on the passengers side, and the rocker cover bolt bungs were perished, so I think it's had a new head on or has had head work in the recent past (only 2 years in UK, so could have been in Japan). If they reused the rocker cover gasket - just a hunch - then it's possible they didn't know enough. If they didn't know enough, it's possible they overtightened. Who knows, though.

widdowson2008 wrote:What would concern me is that BOTH the 'A' bolts could be stripped. Wonder if he has checked that the other 'A' bolt is loose?????

I'll get the rocker cover off again. The other A bolt is inside, right?

In fact, no, not - I'm quite enjoying this! I have to really, don't I?

Driver+Passengers wrote:I'll get the rocker cover off again. The other A bolt is inside, right?
In fact, no, not - I'm quite enjoying this! I have to really, don't I?

Yep - rocker cover off again. The bolt you are looking for is directly opposite the first one but 25mm nearer to the camshaft.
Enjoying yourself? So do I but I'm a sad old fart. What's you excuse?

widdowson2008 wrote:

Driver+Passengers wrote:I'll get the rocker cover off again. The other A bolt is inside, right?
In fact, no, not - I'm quite enjoying this! I have to really, don't I?

Yep - rocker cover off again. The bolt you are looking for is directly opposite the first one but 25mm nearer to the camshaft.
Enjoying yourself? So do I but I'm a sad old fart. What's you excuse?

I learn quick...

Does the threaded hole enter the oilway, or is it a blind hole? Just trying to work out whether oil is getting past the gasket and up the head, or whether it's coming up through the threaded portion and on up...

Driver+Passengers wrote:
Does the threaded hole enter the oilway, or is it a blind hole? Just trying to work out whether oil is getting past the gasket and up the head, or whether it's coming up through the threaded portion and on up...

Not 100% sure, but I would doubt it very much - would be BAD design if it did. Hole should be blind I would have thought. Best guess is oil coming via head gasket.
Been thinking about the Helicoil solution. It would mean head off and all that goes with it - new head gasket, new head bolts, etc.
Plus the fact that I doubt if anyone could tell you exactly how much 'meat' is left in the casting to enable you to fit a Helicoil safely.
If it were me, and I was determined to get it fixed, and particularly if I had stripped off the head in the process, I think I would consider trying to source a replacement casting - probably from a Bongo being broken up.
Which ever way you finally choose to go, you DO realise the amount of work you are letting yourself in for here don't you? Don't get me wrong, I thoroughly enjoyed changing spenners head (first I have ever done) and got a huge amount of satisfaction when it fired up first time, but it was a LOT of work.

Does it loose a lot of oil? Could you live with the loss? and does the oil only come out around the bolt head?

Blimey, what a mess. Loads of work just because some plonker has overtightened the bolt.

Just a thought for a bodge fix. Does it look like its possible to drill straight through, ie down, through this alloy casting and then using a longer bolt get a nut on it underneath as Matt has suggested? or clean it up well and Araldite a stud in?

Not losing a lot of oil at all, at least I wasn't when I had the bolt rattling around in the hole.

It's hard to tell what's leaking past the gasket, as whatever leaks out the hole runs down over everywhere. Might be worth a little drop of instant gasket around the bolt head, seat it all the way down, clean up the block/casting where the head bolts on and see what happens next. Perhaps the increase in oil pressure will cause a greater failure in the gasket - which might be a bad thing. I'm just guessing.

Good point about how much meat is left - from the picture(s) it didn't look as if the existing hole had much material surrounding it and if I remove a couple mm more, there will be less remaining. Agree a replacement casting would be ideal if I got it stripped down that far.

I should check the other bolt.

briwy wrote:Blimey, what a mess. Loads of work just because some plonker has overtightened the bolt.

Just a thought for a bodge fix. Does it look like its possible to drill straight through, ie down, through this alloy casting and then using a longer bolt get a nut on it underneath as Matt has suggested? or clean it up well and Araldite a stud in?

Hi briwy
Let's not put the fear of God up the guy just yet. We don't know if that IS the problem - just a possibility at the moment.
Drilling through? Gotta admit, that has already been suggested by Driver+Passengers but if you take a look at this pic of the casting, it seems a little tricky. Not seen this particular casting in the flesh so can't comment in fairness.
Araldite may be a quick fix solution providing you could sell it on quickly to some honest bloke like Tony Blair afterwards.

Driver+Passengers wrote:Not losing a lot of oil at all, at least I wasn't when I had the bolt rattling around in the hole.

It's hard to tell what's leaking past the gasket, as whatever leaks out the hole runs down over everywhere. Might be worth a little drop of instant gasket around the bolt head, seat it all the way down, clean up the block where the head bolts on and see what happens next. Perhaps the increase in oil pressure will cause a greater failure in the gasket - which might be a bad thing. I'm just guessing.

Good point about how much meat is left - from the picture(s) it didn't look as if the existing hole had much material surrounding it and if I remove a couple mm more, there will be less remaining. Agree a replacement casting would be ideal if I got it stripped down that far.

I should check the other bolt.

If you're not losing much, then perhaps your idea of 'sealing' around the bolt head aint that bad. Certainly worth a punt - nowt to loose.
Don't think you should worry too much about pressure in that area cos at that point the oil is NOT being pumped. It's just a gravity feed back to the sump.

widdowson2008 wrote:

Driver+Passengers wrote:Not losing a lot of oil at all, at least I wasn't when I had the bolt rattling around in the hole.

It's hard to tell what's leaking past the gasket, as whatever leaks out the hole runs down over everywhere. Might be worth a little drop of instant gasket around the bolt head, seat it all the way down, clean up the block where the head bolts on and see what happens next. Perhaps the increase in oil pressure will cause a greater failure in the gasket - which might be a bad thing. I'm just guessing.

Good point about how much meat is left - from the picture(s) it didn't look as if the existing hole had much material surrounding it and if I remove a couple mm more, there will be less remaining. Agree a replacement casting would be ideal if I got it stripped down that far.

I should check the other bolt.

If you're not losing much, then perhaps your idea of 'sealing' around the bolt head aint that bad. Certainly worth a punt - nowt to loose.
Don't think you should worry too much about pressure in that area cos at that point the oil is NOT being pumped. It's just a gravity feed back to the sump.

Of course - you're basically open to the breather coming off the rocker cover at this point. Wonder what would make it splatter up and out, then. Perhaps it's not coming from there...? We basically found a wet splatter on the fibrous stuff up under the saddle - right about this open hole and assumed that the oil came out of there. I still think it's that, though.

If you don't think I'd be changing the dynamics of the system much by replacing the bolt and sealing around the bolt head, I'm keen to try that.

Driver+Passengers wrote:
Of course - you're basically open to the breather coming off the rocker cover at this point. Wonder what would make it splatter up and out, then. Perhaps it's not coming from there...? We basically found a wet splatter on the fibrous stuff up under the saddle - right about this open hole and assumed that the oil came out of there. I still think it's that, though.

If you don't think I'd be changing the dynamics of the system much by replacing the bolt and sealing around the bolt head, I'm keen to try that.

Sealing up this way shouldn't affect the dynamics at all, cos it's supposed to be sealed.
Sealing the bolt head may not be enough to stop the leak, however, it may show up the main leak zone more.

widdowson2008 wrote:

Driver+Passengers wrote:
Of course - you're basically open to the breather coming off the rocker cover at this point. Wonder what would make it splatter up and out, then. Perhaps it's not coming from there...? We basically found a wet splatter on the fibrous stuff up under the saddle - right about this open hole and assumed that the oil came out of there. I still think it's that, though.

If you don't think I'd be changing the dynamics of the system much by replacing the bolt and sealing around the bolt head, I'm keen to try that.

Sealing up this way shouldn't affect the dynamics at all, cos it's supposed to be sealed.
Sealing the bolt head may not be enough to stop the leak, however, it may show up the main leak zone more.

Thanks for all your input on this, Steve. Really appreciated!

By removing any leak from this bolt hole, I can only imagine that any continued leak would therefore come from the head gasket around the oil return. I'll get onto this over the weekend, and see how she does.

Flying by the seat of my pants here. Only trying to apply a bit of logic to get a solution. If there is anyone has other ideas, please shout up.

widdowson2008 wrote:Flying by the seat of my pants here. Only trying to apply a bit of logic to get a solution. If there is anyone has other ideas, please shout up.

Ditto on all three counts!