Peugeot 406 Coupe - 3.0L V6. Complete refurb... very slowly
Discussion
shalmaneser said:
Really impressive stuff you're getting on with here, and it sounds like you've been through the wars with personal stuff too.
Oh there was even more than that, it's been a rough decade, we'd only just lost my other nan and grandad, and a couple of more distant relatives too, and I lost a couple friends to accidents right around the same time, it was hell - and I basically ended up as a carer for many years after to stop what was left of the family doing anything silly too. Not much fun. It's why the buggy revamp took so long too.Anyway, the tanks I posted up above that I'm making right now, I had prior form with - whilst on a long drive I suddenly started slowly loosing coolant. When I parked the car up there were no leaks - it only lost it when the car was hot and everything was up to pressure. That was a bit worrying as that's often a sign of a headgasket leak but there was no misfire or oil and coolant mixing - anyway, I doubled checked all the radiators and hoses, checked the hose clamps, couldn't find it, so I threw some UV leak detector in expecting a pinhole in the radiator, nothing showing, but I got a little shine right at the back of the engine bay, cue one degassing tank:
Now after some research I found they all start leaking and they're no longer available, so I started looking at why and if I could fix it - it turns out these tanks are made in two halves and ultrasonic welded at the seam.
Only they're welded very badly, to the point there's basically only a small flashline that's actually welded - they weren't done with enough pressure or for enough time at the factory, someone was obviously saving a few seconds of cycle time to crank them out faster - I've seen people saying they had 1 or 2 tanks replaced even under warranty when they bought the car new.
You can see how the weld had split and the tank opens up under pressure here:
Peugeot changed the design for later engines and went with a welded polypropylene tank instead of these Nylon 6.6 + glass fibre ones, however, the shape is different and so are the outlets and angles, so they won't fit in the stock location, it's very tight down at the back of the bulkhead down there.
Now, some might know this, but bonding nylon together is a nightmare even fresh, when it's aged, been heat cycled and absorbed coolant (it'll take about 8% of it's volume in water when saturated, it's a lot!) over the years it's nigh on impossible to bond with decent structural strength to the point I'd trust it with pressure and boiling hot coolant - and the inside was full of stress cracking and bubbles under the surface where the tank and fittings had flexed and coolant had worked its way under the surface:
So, if I can't get a replacement, I can't glue it back together, and I don't trust trying to weld it with heat and fresh nylon because of the internal cracking, I came up with the next best thing I could think of - clamp the two halves together onto a seal.
So I dried the tank at 100c for 8 hours to drive out as much of the absorbed moisture as I could, I sanded back the flanges where the two halves of the tank met, washed it down with solvent and then flame treated the flanges to get the surface energy up to try to help things bond - then put a good bead of 3M copper silicone sealant between them and clamped them down with a controlled gap (half a mm) so it didn't get squeezed out completely while it set.
Then to hold the two halves together against the pressure of the cooling system, I welded a couple of washers to jubilee clip to make a self centring clamp, and I printed two washers in PCTPE (a form of soft flexible nylon I had on hand for making prosthetics) to spread out any stress from the clamp given it would otherwise be on the flat area of the tank where it's the most flexible/weakest, et voila, one repaired tank:
Which worked pretty well for maybe 6 years or so, but given I've kinda spoilered this already - those internal stress cracks in the tank eventually worked their way through and it started blowing coolant out of the top instead last year
But hey, my seal never leaked!
....and yes, that does look like a polyurethane engine mount that it's sat on there....hmm, wonder why...
Edited by PhillipM on Tuesday 20th February 15:38
Cambs_Stuart said:
I'm really enjoying this thread! Your problem solving and technical skills are just brilliant.
Sorry to hear about all the non-car stuff. I suspect there are a few people on here (myself) included that use tinkering with cars as a release/escape from other stuff.
Yes, I think it's pretty common given some of the people I'm often talking to with race stuff, etc. It's a good distraction and you learn new stuff along the way, works well Sorry to hear about all the non-car stuff. I suspect there are a few people on here (myself) included that use tinkering with cars as a release/escape from other stuff.
Since I'm already talking about the tanks anyway, the replacements I was making this week fit perfectly, it's pretty tight in the OE clamp and fitting, you couldn't get a cig paper between the flanges and bolts and the clamp, pretty happy with that:
And the hoses fit perfectly too:
The layer lines look way worse on camera, my Pixel seems to oversharpen everything, Google need a kick
Edited by PhillipM on Tuesday 20th February 16:23
Cheers, I know a lot go through worse, but we each have our own personal hells, I think. Things are getting better, that's the main thing.
Anyway, as was featured in the last update there, I started playing around more with the printed bits, and made myself a honeycombed lower engine mount - this had internal geometery to make it progressively spring much like an OE mount, just stiffer, so apart from the mirrors vibrating a touch at idle, the NVH was great:
However, I very quickly learned about the need for annealing polyurethanes near warm engine blocks and exhaust manifolds, as it eventually distorted slowly from compression set
So I went down an entire materials chemistry rabbit hole for a while, did a whole lot of annealing testing on different printable polyurethanes, discovered that 80% of the resins that were printable were completely useless for elevated temps even if their spec sheets claimed otherwise, and found out how difficult keeping that tiny honeycomb pattern in any sort of tolerance was when you're annealing soft parts at 100-140c for a day or two...it worked on larger patterns, like for these prototype exhaust mountings:
...but not the smaller ones necessary for the engine mounts to allow them to fold up to increase the spring rate vs displacement.
Cue some time later (yep I'm skipping timeline a bit again) prototype two in some Lubrizol and BASF resins that microfoam internally, turning into basically a polyurethane sponge - like your suspension bumpstops often are - giving me the same effect as the honeycomb, with less hassle for post-processing work:
But also required entirely reworking the geometery, so I basically threw my old design away and started again.
This stuff lets me also print a hard outer with a softer inner so I made it in two halves for easier fitting on this one.
And while I was at that after all that work I went down a rabbit hole of mountings for friends cars and retailers and pretty much ended up as the go-to guy for obscure car engine/exhaust mountings where NVH was an issue with polys, so I guess my rabbit-holing worked out okay there in the end
Oh, and I did find the pic of few adaptors for some of the audio upgrades I already mentioned, that I didn't really document unfortunately, like these baskets that let me drop some nice silk dome ferrofluid cooled mids/tweeters in the dash, because the stock tweeters sounded like crap and one had blown anyway:
A guy that had two sets swapped me a set of them for a set of adaptors for his, worked out well
I managed a similar trick for some carbon coned Focal 6.5" low-mids for the front doors, and got lucky with a very cheeky bid on some old stock GTO250 JBLs in the rear 6x9 parcel shelf cut outs to replace the budget JBL 6x9's they come with stock. Left the standard amp in but it really, really cleaned up the audio a lot for very little outlay, which was nice.
Eventually I managed to get another matching set of the tweeters to stick in the rear door cards too, because the guy I swapped for the first set eventually went to some even sillier spec audio so I printed him some adapters for his new ones in exchange for that old pair
Anyway, as was featured in the last update there, I started playing around more with the printed bits, and made myself a honeycombed lower engine mount - this had internal geometery to make it progressively spring much like an OE mount, just stiffer, so apart from the mirrors vibrating a touch at idle, the NVH was great:
However, I very quickly learned about the need for annealing polyurethanes near warm engine blocks and exhaust manifolds, as it eventually distorted slowly from compression set
So I went down an entire materials chemistry rabbit hole for a while, did a whole lot of annealing testing on different printable polyurethanes, discovered that 80% of the resins that were printable were completely useless for elevated temps even if their spec sheets claimed otherwise, and found out how difficult keeping that tiny honeycomb pattern in any sort of tolerance was when you're annealing soft parts at 100-140c for a day or two...it worked on larger patterns, like for these prototype exhaust mountings:
...but not the smaller ones necessary for the engine mounts to allow them to fold up to increase the spring rate vs displacement.
Cue some time later (yep I'm skipping timeline a bit again) prototype two in some Lubrizol and BASF resins that microfoam internally, turning into basically a polyurethane sponge - like your suspension bumpstops often are - giving me the same effect as the honeycomb, with less hassle for post-processing work:
But also required entirely reworking the geometery, so I basically threw my old design away and started again.
This stuff lets me also print a hard outer with a softer inner so I made it in two halves for easier fitting on this one.
And while I was at that after all that work I went down a rabbit hole of mountings for friends cars and retailers and pretty much ended up as the go-to guy for obscure car engine/exhaust mountings where NVH was an issue with polys, so I guess my rabbit-holing worked out okay there in the end
Oh, and I did find the pic of few adaptors for some of the audio upgrades I already mentioned, that I didn't really document unfortunately, like these baskets that let me drop some nice silk dome ferrofluid cooled mids/tweeters in the dash, because the stock tweeters sounded like crap and one had blown anyway:
A guy that had two sets swapped me a set of them for a set of adaptors for his, worked out well
I managed a similar trick for some carbon coned Focal 6.5" low-mids for the front doors, and got lucky with a very cheeky bid on some old stock GTO250 JBLs in the rear 6x9 parcel shelf cut outs to replace the budget JBL 6x9's they come with stock. Left the standard amp in but it really, really cleaned up the audio a lot for very little outlay, which was nice.
Eventually I managed to get another matching set of the tweeters to stick in the rear door cards too, because the guy I swapped for the first set eventually went to some even sillier spec audio so I printed him some adapters for his new ones in exchange for that old pair
Edited by PhillipM on Tuesday 27th February 17:34
Oh and I made some inserts for the upper engine mount/torque bushings as well, forgot about those:
I think it just got driven around for a while after that, but a few months later, it started to get a little clutch slip just on odd occassions - not enough to slip in daily driving but I could feel it flare a little when changing up gears, and you'd occasionally get a whiff of hot clutch material.
The gearbox never felt too great when shifting - someone had put the wrong oil in it at some point in it's life - and Peugeot synchros really don't like that - even me putting the right stuff in only improved it somewhat, it would still baulk on high rpm changes - so I thought screw it, I'll pull the gearbox out and flush it through, slap a new friction plate in it and I'll be done.
However when I pulled the clutch and flywheel out they looked rather worse than ideal....
...it ended up needing a bit more work than I thought...
I think it just got driven around for a while after that, but a few months later, it started to get a little clutch slip just on odd occassions - not enough to slip in daily driving but I could feel it flare a little when changing up gears, and you'd occasionally get a whiff of hot clutch material.
The gearbox never felt too great when shifting - someone had put the wrong oil in it at some point in it's life - and Peugeot synchros really don't like that - even me putting the right stuff in only improved it somewhat, it would still baulk on high rpm changes - so I thought screw it, I'll pull the gearbox out and flush it through, slap a new friction plate in it and I'll be done.
However when I pulled the clutch and flywheel out they looked rather worse than ideal....
...it ended up needing a bit more work than I thought...
Edited by PhillipM on Wednesday 28th February 00:19
Okay, so since I needed to resurface that very heat warped/spotted flywheel, and I needed to take a fair cut to skim under those hard carbide deposits, the little devil on my shoulder - who's also a moron - whispered in my ear;
"Well, you should also make it lighter, you didn't like how lazy the engine response was, right? Go on. Do it. Take a big cut in the lathe. It'll be fine, your passenger might lose a leg if it explodes but that's a risk we're willing to take..."
The idiot holding the lathe handle fortunately has twice as many brain cells (two) and went off to do some CAD simulations first.
I took a few hardness readings and made an educated guess on what the actual spec of the cast steel was for the flywheel, worked out where I could take out most of the material around the outside and keep things with a considerable safety margin and some generious radii into any transitions to remove any unexpected stress concentrations, and what we then ended up with instead of this stock flywheel after a cleanup:
Was this:
...and yes, I did 3d print both the drill jig and the rear profile former to follow on the lathe. Hammer, nail. (By this point my printers were ridiculously accurate anyway running with preloaded linear rails, ballscrews and other tricks, more than good enough for this work) And yes, that drilling work was tricky, on two edges, I used a fancy 3 flute drill and reamer for it.
I then did a static balance using the old bearing and cone method:
And just tweaked material away until I got the imbalance down to about 1/4 of the stock one, more than close enough, it's thin enough not to need a dynamic balance.
And then it got prettied up to protect the machined surfaces:
That gave me a flywheel that's about 2.5kg lighter than stock - 6kg instead of 8.7kg - but more importantly because of all the weight I lost around the outside edge, it's almost half the inertia of the standard flywheel. Much better.
"Well, you should also make it lighter, you didn't like how lazy the engine response was, right? Go on. Do it. Take a big cut in the lathe. It'll be fine, your passenger might lose a leg if it explodes but that's a risk we're willing to take..."
The idiot holding the lathe handle fortunately has twice as many brain cells (two) and went off to do some CAD simulations first.
I took a few hardness readings and made an educated guess on what the actual spec of the cast steel was for the flywheel, worked out where I could take out most of the material around the outside and keep things with a considerable safety margin and some generious radii into any transitions to remove any unexpected stress concentrations, and what we then ended up with instead of this stock flywheel after a cleanup:
Was this:
...and yes, I did 3d print both the drill jig and the rear profile former to follow on the lathe. Hammer, nail. (By this point my printers were ridiculously accurate anyway running with preloaded linear rails, ballscrews and other tricks, more than good enough for this work) And yes, that drilling work was tricky, on two edges, I used a fancy 3 flute drill and reamer for it.
I then did a static balance using the old bearing and cone method:
And just tweaked material away until I got the imbalance down to about 1/4 of the stock one, more than close enough, it's thin enough not to need a dynamic balance.
And then it got prettied up to protect the machined surfaces:
That gave me a flywheel that's about 2.5kg lighter than stock - 6kg instead of 8.7kg - but more importantly because of all the weight I lost around the outside edge, it's almost half the inertia of the standard flywheel. Much better.
Edited by PhillipM on Wednesday 28th February 12:17
Next up, very quickly flush out the gearbox and put things back together with a new friction and pressure plate, job done, right?
Oh. And no, that's not rust. Someone's used one of those terrible oil additives presumably trying to 'fix' the baulky gearchange, and it's left this horrible coating of a soft discoloured almost plasticised oil over everything...so a complete strip and clean of the box and a couple of new synchro cones later...everything went back together looking almost brand new:
And a clean and a coat of paint on the casings was added to finish it off, plus I left a note for the next owner, just so they know:
...however, the driveshafts were looking pretty sorry for themselves now that the flywheel and gearbox had had the royalty treatment....seems a shame to put those back on as they are (yes, this is how it always goes, I do one job and end up with 6 more on the go)....
Oh. And no, that's not rust. Someone's used one of those terrible oil additives presumably trying to 'fix' the baulky gearchange, and it's left this horrible coating of a soft discoloured almost plasticised oil over everything...so a complete strip and clean of the box and a couple of new synchro cones later...everything went back together looking almost brand new:
And a clean and a coat of paint on the casings was added to finish it off, plus I left a note for the next owner, just so they know:
...however, the driveshafts were looking pretty sorry for themselves now that the flywheel and gearbox had had the royalty treatment....seems a shame to put those back on as they are (yes, this is how it always goes, I do one job and end up with 6 more on the go)....
shalmaneser said:
Interesting it's got a single mass flywheel as standard, I would have expected dual mass. Seems to me very little risk shaving it down a bit in that case. How does it rev, I would love to see a before and after vid!
Dual mass flywheels are very much more common on diesels to help with NVH. Really not needed on a smooth V6.I was pleased to find a single mass on my 5.7 V8 Monaro when the clutch kit was changed.
Yep, and dual mass flywheels are often to protect the gearbox too, from the massive torque spikes from heavily boosted diesels these days, not really an issue on a smooth old petrol V6 with what's basically a commercial van gearbox strapped to the side of it - the gearbox is overkill on these, it'll take another 100lbft+ of torque no problem even within manufacturer spec.
The later V6 engines had a "Dual Mass" flywheel - but unlike a modern sprung system it was basically the same as a crank pulley with a ring of rubber in the centre - it just made idling and engaging the clutch smoother.
The later V6 engines had a "Dual Mass" flywheel - but unlike a modern sprung system it was basically the same as a crank pulley with a ring of rubber in the centre - it just made idling and engaging the clutch smoother.
Edited by PhillipM on Wednesday 28th February 19:53
PhillipM said:
Yep, and dual mass flywheels are often to protect the gearbox too, from the massive torque spikes from heavily boosted diesels these days, not really an issue on a smooth old petrol V6 with what's basically a commercial van gearbox strapped to the side of it - the gearbox is overkill on these, it'll take another 100lbft+ of torque no problem even within manufacturer spec.
The later V6 engines had a "Dual Mass" flywheel - but unlike a modern sprung system it was basically the same as a crank pulley with a ring of rubber in the centre - it just made idling and engaging the clutch smoother.
My 996 has a dual mass flywheel - apparently a single mass make a bit of a rattle when in neutral due to resonances in the gearbox?The later V6 engines had a "Dual Mass" flywheel - but unlike a modern sprung system it was basically the same as a crank pulley with a ring of rubber in the centre - it just made idling and engaging the clutch smoother.
Edited by PhillipM on Wednesday 28th February 19:53
Yea the transaxle in the buggy has the same issue, rattles at idle with the aggressive clutch plate and light flywheel unless you tickle the pedal. Not fitting a dual mass to that one though
I'd imagine your transaxle is a bit more stressed in a 996 than the 'box in the 406 though
I'd imagine your transaxle is a bit more stressed in a 996 than the 'box in the 406 though
Edited by PhillipM on Thursday 29th February 12:26
Okay, onto the driveshafts - there wasn't a whole lot wrong with these, the intermediate shaft ball bearing was a bit dry and had a little bit of play, so I pressed that off and replaced it - they're a standard size so only a couple of quid from a bearing supplier - I stripped the CV joints too, but there wasn't really any wear at all, although one boot had lost some grease from a pinhole, and both outer boots had been replaced with the cheap stretchy rubber ones at some point.
Since I'd done everything else properly, and I really didn't want to be take shafts back out later on - I ordered the OE GKN kits with the hard OE plastic-type boots, new steel clips, new CV balls and some decent moly grease, I stripped, cleaned and replaced everything, gave the shafts a sandblast and a coat of paint, refinished the surfaces where the seals on the gearbox end, and fitted a couple of new ABS reluctor rings just because they're only a couple of quid anyway. Just in case:
That combined with the new diff seals in the gearbox should mean they're not a worry for a long time.
I got everything back together and bolted into the car, added some special sauce gearbox oil - Peugeot boxes of this era are picky about oil (and I did the rabbit-hole thing again on gearbox oils many many years back) so I run a lighter weight oil made from a better base, that I use for them instead of the usual BV75w80 - it usually makes them shift very cleanly and quickly - at the expense of needing replacing every couple of years instead.
So off out for a test drive - you can probably tell why I wear out suspension bushes a lot given the road....
The good news was, with the lighter flywheel the engine response now is really nice and sharp and snappy, the car feels much more lively in the first couple of gears as well, and it doesn't really have any downside bar it needs a tickle of throttle now in traffic otherwise you'll get a little bit of clutch shudder, not a problem at all.
The gearbox went from baulking and taking a second or two to change at any RPM over about 5k, to shifting smooth as butter even when it's cold, and no hesitation at all into any gear even at the redline, huge improvement, in fact it feels better than any of these ML boxes I've driven in anything else, so I was pretty happy with the work there, even though it turned into 10x as much as originally intended.
Since I'd done everything else properly, and I really didn't want to be take shafts back out later on - I ordered the OE GKN kits with the hard OE plastic-type boots, new steel clips, new CV balls and some decent moly grease, I stripped, cleaned and replaced everything, gave the shafts a sandblast and a coat of paint, refinished the surfaces where the seals on the gearbox end, and fitted a couple of new ABS reluctor rings just because they're only a couple of quid anyway. Just in case:
That combined with the new diff seals in the gearbox should mean they're not a worry for a long time.
I got everything back together and bolted into the car, added some special sauce gearbox oil - Peugeot boxes of this era are picky about oil (and I did the rabbit-hole thing again on gearbox oils many many years back) so I run a lighter weight oil made from a better base, that I use for them instead of the usual BV75w80 - it usually makes them shift very cleanly and quickly - at the expense of needing replacing every couple of years instead.
So off out for a test drive - you can probably tell why I wear out suspension bushes a lot given the road....
The good news was, with the lighter flywheel the engine response now is really nice and sharp and snappy, the car feels much more lively in the first couple of gears as well, and it doesn't really have any downside bar it needs a tickle of throttle now in traffic otherwise you'll get a little bit of clutch shudder, not a problem at all.
The gearbox went from baulking and taking a second or two to change at any RPM over about 5k, to shifting smooth as butter even when it's cold, and no hesitation at all into any gear even at the redline, huge improvement, in fact it feels better than any of these ML boxes I've driven in anything else, so I was pretty happy with the work there, even though it turned into 10x as much as originally intended.
Edited by PhillipM on Thursday 29th February 12:49
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