Mysteries unravelled in rebuild... a long involved story

[AlanS]

I suppose living this side of the "Pond" I hear more about the BX TZi (with the DKZ engine) using oil than you guys would with the predominance of the soup burners over there, but it has been a long ongoing issue particularly with low mileage cars over here.
I've been living in denial with it for a few years as have plenty of others, even PSA/Citroen "mentioned" (or should that be warned?) of oil useage and explained it as being part of engine design, but the fact remained that no matter what was said or what kind of cures and mods were done, they still burnt/used far too much oil and this was regardless of the grade used.
I actually once tried leaving brake fluid in the ehngine via the plugholes once which improved the performance by at least 10% and oil consumption by as much. Others had "modified" the breather system and included what was in effect a "catch can" to the system as a type of improvement although I suspect all this did was reduce crankcase pressure which in turn resulted in less oil being burnt.
Symptoms were quite strange. Never did I see smoke come from the exhaust, apart from one occasion when I was driving up my street and it really laid a smoke screen down. By the time I'd hit the end of the street, it was all gone; weird!
The clutch on this car right from when it was bought with 90,000 klms on it up until it was layed up a couple of months ago, was always a "knee under the chin" job whenever you let the clutch out and although it was adjusted early in the piece, the clutch never seemed right and wastouchy to say the least. Had a lower engine mount go once and sure enough, the clutch went all out of adjustment. Fixed the mount and that sorted the clutch.
Whilst I've been a tradesman all my working life who even when I worked in a collar and tie, still held a connection to all things mechanical both workwise as well as socially through involvements with auto clubs, the son who drives it, is more an academic with only a small passing interest in anything mechanical, hence when a warning light comes on, it's not a case of why is it on, but more one of "I wonder if there's a wiring problem causing this?" and often doesn't mention these incidents until the car stops, as a result, the coolant in the 2 cases I know of where it was driven until almost glowing and just totally stopped (in a ball of steam, smoke and rattles) on the side of the road and then filled up with tap water "until I get the leak fixed properly and then I'll put coolant in" plus the comment that the car was "sluggish" at roundabouts and the engine seemed to be screaming a lot which turned out to be a totally cooked clutch were 2 jobs on the agenda until the head gasket gave up the ghost and he had to park the car up.
When we ripped the entire mechanicals out and removed the head, first thing that greeted us was the head gasket that came out as a rectangular strip about 6mm wide. Where's the rest? In the water jacket! It seems the material they make head gaskets from doesn't really take kindly to no coolant and getting superheated as well.
The head didn't exactly fall off either with one headholt managing to snap off in the thread; what a treat that was, fortunately, I have a mate with a lathe so we turned up a guide 55 mm long X I think it was 11 mm diameter and with a 1.5mm taper and a 4 mm hole through the centre so a pilot drill could be put through (drill bit was a special one both in material, length and bit end shape and cost A$40+) which then had to be opened out to take an 8mm bit which fortunately grabbed the broken part that had sat in vinegar and then penetrene for a week and screwed it out the bottom. This seemed to have been cause by the head trying to buckle when red hot and allowing water to seep down the bolt shaft and onto the threads which then simply rusted in the threaded area of the block, grew and just would not turn.
The flywheel looked pretty good; no grooves etc, so the best suggestion was to just deglaze it. I have a highspeed random orbital sander, so decided to just knock the shine off. When I hit it with what was a fairly light grade disc, I notice all these little discoloured patches appearing on the surface...bummer; it's hotspots. I take it to a guy who works on racing cars and is a clutch specialist. He's the original "Never judge a book by its cover" type. Hair down his back in a pigtail that gets washed once a year whether it needs it or not, daggy beard surrounded by 7 days growth and sucking on a can of Coke and two fags as his dinner. Unlike most over here, doesn't bolt at the name "Citroen" in fact recognises it, mumbles something as I drop it on his bench, so when I collect, he tells me it "was like most of these I've done; faced the actual face but normally, I need to grind the areas where the pressure plate bolts on. In this case and a few others I've done, the dimension wasn't right, but after I'd faced it, it was then. Betcha had some strife getting this to feel right when you adjusted it?" Apparently, some of these flywheels are a bit out in this dimension when they're made. Might be something worthy of you guys who have had ongoing clutch problems checking out next time you have one apart.

With the engine on a stand, I start to remove the sump.....again, studs in so hard and corroded as we discovered, that the ratchet starts to feel springy as I try to undo. Feels like I'm going to have more snapped off studs, so I resort to a rattle gun. All out with no dramas; good tip next time possibly for removal of head studs also.
Disconnect the big ends, tap out pistons, then discover the sleeves (that all the manuals tell you to use holding down bolts on so they won't fall out) are so tight you'd almost think they were a shrink in fit and in fact in reality, these are, as the seals can be seen poking out from under them, yet there has been no leak into the sump from them. It takes around 3 hours of tapping, heating, oiling, flogging and swearing to remove them. There was signs that the sleeves had actually "grown" into the block possibly again through excessive heat and had in effect sealed themselves without any assistance from the liner seals: amazing.
Now a detailed inspection to see why this thing was performing as well as it was whilst still using excessive oil:

The compression rings ranged from some which were jammed solidly in their grooves to others which were just "coked" in.
The oil rings on each piston were as much use as a tit on a bull; hopeless.
There was signs that the oil had been going straight past the oil rings but the compression rings were so snug a fit that in most cases it seemed to have sneaked past the centre (compression) ring but was halted by the top one, so presumeably, the thin coating of oil that would be left on the wall is the reason for the oil consumption.
Glazing wasn't really an issue, although there were signs that showed a very slight top lip, so I honed the entire sleeve and roughed it up anyway.
The oil rings.............ah yes, the dreaded useless oil rings. How they ever came up with this idea is anyone's guess.
Over the years, most oil rings (including the ones I have to go into the engine) have been of the 2 chrome cords held out by an expander variety, but not these. These are held by what appears to be a spring that sits in the groove and the oil ring sits on top of the outer edge of it. The last time I saw oil rings like this was on a 16V which was burning oil like it was going out of style on one cylinder on a 16V that had been imported from the UK, and sure enough, this style of oil ring was fitted to the cylinder doing all the oil buring. I can't see any way in the world these things can work effectively, so hopefully all of these mysteries will cease to exist once it's back on the road.
The head is due back from the machine shop in the next few days, and again I've used some of the race car guys so I know it will come back done to perfection (and usually charged for accordingly, athough 'mates rates' are involved as well) so I don't have to to get involved with setting tappets via shims as I'm getting the valves faced and the seats cut and a new thermostat is going in as a safety measure.
Hopefully, all should go well and I'll report back when it gets a few thousand klms on the clock as regards the difference in sound and performance and to let you know if the problems associated with the oil consumption have in fact been found and fixed.


Alan S

[Philip Chidlow]

Wow Alan... It'll take a littel time to respond... that's a lot of words - worthy of an article in the Citroenian?

[jeremy]

Interesting discoveries Alan. I was very surprised when looking at Haynes to discover that Citroen were using a one-piece oil ring (perhaps with an expander) and yet these engines were capable of enormous mileages (especially diesels) without serious oil consumption problems.

I'd always regarded the single piece ring (Slotted Scraper) as being rather old fashioned. Its construction is of course such that it has an upper and lower thin ring separated by cast metal - and its weakness is that when the thin rings wear back to their support they cease to do their job and the engine quite rapidly starts to use gallons of oil.

The later 3 piece ring you describe has always seemed to me to be superior as the 2 rings themselves seemed to be made of very hard metal and potentially could wear till they wore through without giving the 'thick' ring I described above.

Good luck with the rebuild - sounds as though you should have a really good engine when its all done.

[m_2975]

Hi there Alan.

Can't say that we have had any problems with the bottom end of the DKZ in our 15 years of experience with them. Normally we only find that the valve stem seals are the oil burner culprit. In the days of the BX with a DKZ (1988-1993) we actually had them coming in for new valve stem seals under warranty. Most didn't make it to 80,000kms without them being done (a bit like the auto transmissions but we won't go there!).

My 1993 GTI is an Australian TZI and used to use a small amount of oil. It had about 140,000kms on it at the time and was driven once every few weeks. It's now done 170,000kms, driven daily and has never had the head off nor any work to the seals. Now it doesn't use a drop of oil or coolant! When I give it a service I have exactly 5 litres of waste oil and put in 5 litres of fresh oil. The dipstick now has an imprint at the top notch where the oil always sits. I check the coolant once a week along with the oil and it's just that, a check. No filling at all.

Our other TRI estate has now clocked up 300,000kms of hard city driving. It was in the basket like most whereby it had the valve stem seals done at 60,000kms, auto transmission at 90,000kms, then the valve stem seals done again at 150,000kms but then nothing until 298,000kms. The transmission too needed to be done at 298,000kms and was all done at the same time.

Between 150,000kms and 280,000kms his car never used a drop of oil but started to slowly use oil and water.
Now it's set right again.

In summary these engines do need a bit of work from time to time but for some reason you can have ones that never need to be touched and others that need regular attention. I feel that if they are done properly, serviced right and have good oil they are perfect.

The oil that we use and have been using for the past 10 years is Valvoline DuraBlend 15W50.

I firmly believe that this oil is the best for a DKZ engine. My GTI is now on it and uses no oil, our estate is on it and the distance between seal changes has doubled.

Give it a go for a few months Alan. I highly recommend it for all BX's.

This might also be the reason why we haven't ever had any problems with the bottom ends, even on the 300,000kms engine.

All the best.

[Doz]

My 2 earlier 16's (both MK1's) I showed over 200,000 miles and never had the head of either... cams, yes, but never actually took the head off. Neither burnt a drop of oil between changes.

[Doz]

I'll refine that , when I owned them I never took the heads off ... someone may have done previously of course... I bought them both at about 70k each.

[AlanS]

Over the years, I've found that in particular low mileage DKZs (122 BHP engine) has had a reputation for oil burning, so much so that it has been claimed by many that either the handbook or in some cases dealers have advised owners of up to 1 litre per 1000 klms as being "acceptable" oil useage.
The same applied to Peugeots which had the same engine and in the case of Peugeots I understand that any complaints to dealers whilst the car was under warranty, resulted in the engine having different oil rings fitted, however in true Citroen tradition, it wasn't until the owners were almost beginning to threatren violence before any action was taken, as a result, many Cits went under the radar and still have the original rings and as a result we still often get threads on aussiefrogs from owners, often ones who have just bought a car, asking if it's normal.
It was so common that the Citroen Car Club of Queensland ran an article in their newsletter a few years back advising ways and means of lessening which included reorganising the breather system (as I mentioned previously) but the common denominator with most has been that the ring design was the main problem.
Strangely, not all do it, which begs the question was it the way some were run in or did some cars come through with the different oil rings fitted, or as I know used to often happem with Fords and Toyotas when I worked with them, if a car was found at PD (pre-delivery) to have a glaring fault, it was repaired before it either went on the floor or was delivered, so perhaps smokey cars were done prior to the new owners receiving them?
It is a problem almost unheard of on the lower hp Tri engine (DFZ?) or on the 1.6 which must have had the conventional rings fitted.
The system used on these would never have worked efficently; it is just a dog of a design. I also note that a couple of compression rings were jammed in their grooves also and note that the replacements show a slight taper and recommend which way that has to be fitted on installation of the rings on the pistons, again, something the originals didn't have and as a result I feel lack of movement caused the jamming, a problem now overcome.
The sleeves are now a nice smooth slip in fit since I cleaned everything up in that area and as the big end slippers arrived last night, I can now start reassembling...............as soon as I find my ring compressor; that long since I used it, I might need a driving lesson on it before I start.


Alan S

[jeremy]

I think its commonly reconed that replacement rings are generally a better design and quality than those fitted by manufacturers.

To be fair to the manufacturers they probably get a better bore finish than many reconditioners - and so the things will have less of a job bedding in etc.

The top replacement ring is generally a 'Ridge dodger' with a small step in its top edge.

Haynes in the supplement for the 16 valve engine does show a tapered middle ring with the taper pointing downward. There seems on a quick look to be no similar drawing for the single cam engines. I suppose its possible that a maker of after market rings would supply the same for all 1905 engines - or engines sharing the same bore.

Its not quite as simple as it seems - Land Rover developed their Turbo-diesel engine (not the direct injection one) and all was well on durability tests - then when it came to manufacture the ring supplier couldn't get the right steel - so substituted a more expensive one which they considered better - but the things started burning oil quite early on and they all had to be replaced - including the ones purchased by the Army (6000 vehicles?)

[AlanS]

Jeremy,

From what I've been told, Citroen/PSA in their "wisdom" were experimenting with a different style of ring. Why, if the others were doing the job, only they would know.
When pulled off the piston, they are as you described, a single ring about 3mm wide with a wire coil (not a spring as it first appears) sitting in the ring groove and this appears to have managed to embed itself in the back of the ring as well as the coils sitting on a slight angle, at which point it has almost no outward tension on it. Inside the ring groove there are holes to allow for oil to spray through into the groove as the piston goes down so as to lubricate the wearing surface on the bore.
IMO, the oil coming through these holes which whilst being fairly minute almost as a spray or vapour but under a certain amount of pressure, then is forced into the oil ring groove, but between the two surfaces that contact the bore, so in effect, only one would then be trying to wipe the oil off the bore as the piston descended and the groove would no doubt be constantly full of oil, as a result a film would be left on the cylinder wall which would supposedly be wiped off but from the signs of carbon and burnt oil up the sides of the piston, was getting past the bottom compression ring and a lot of it past the top one and in so doing was possibly being expelled with the exhaust rather than being burnt on the expansion stroke which would explain the lack of blue smoke.
Heavy carbon deposits on the injectors which I cleaned a couple of years back couild also be attributed to this strange phenomena.
The fact that the rings were a one piece instead of a 2 rings and an expander type and seem to be of a hardened metal with highly polished contact surfaces and virtually no ability to flex as well as rigid compression rings with a habit of seizing in their grooves seems to explain this oil consumption. I have refrained from using the word "burning" as this infers it was a "smokey" which it NEVER was and perhaps if we had the MOT emission checks that you guys have, it may have been picked up much sooner but then again, if it was doing it at the time of the cycle I suspect it was, maybe it wouldn't.
Maybe we still have someone on here who may have had one of these with the problem who can tell us if it did in fact affect the emissions test.


Alan S

[jeremy]

Alan

Wet liner engines can be a bit strange - although the French did love them and presumably got over the problems. The one with problems which springs to mind was the Ferguson Tractor diesel - which was a cousinn of the Standard Vanguard engine (with a block which was enormously thick in places).

While a good diesel for the 50's it always suffered from being rather difficult to start - which was attributed to poor compression due to liner distortion.

I wonder how much distortion there is in an XU liner. I believe this problem raised its head again in the British Leyland / Rover K series but this horror has so many joints that its bound to leak somewhere and I suppose its a miracle that its as reliable as it is. (Head bolts hold the bearing caps on! - I'm not sure if you remove the head the crank drops out)

There are many theories on piston rings - but of course with extended use everything conspires against them. When the pistons are new, with clean and tight ring grooves there is nice conduction of heat into the cylinder walls etc. As it all wears and gets covered in carbon - this will become less efficient, oil that would otherwise have returned to the sump will be burnt - leaving further residues and so it goes on. The rings will loose their tempering and exert less pressure - so poorer heat conduction and so it goes on.

In fact when you think about it its a miracle they last as long as they do!

I saw somewhere that the designers of the XU were influenced by some new (then) theories about ring/bore wear which came from Ricardo (descendants of the dreaded Ricardo Comet diesel pre-combustion chamber). I think that the theory was that precise temperature control was essential for exceptional piston/bore life. One day when I'm really bored I'll try and find it.

[AlanS]

Strangely, these engines apparently were oil users right from the day they came off the assembly line and in reality, never seemed to get any worse, in fact there are cases where they did improve slightly as ours did.
Just been to the machinists place now and was asked what we were using in this engine as it had what appeared to be like a slimey black gummy stuff over the back of the valves and up in the recess above the valves which he reckons could confirm my theory (which at first he had problems agreeing with) that the engine has been sending oil vapour out with the exhaust, unburnt and it just cooks away in the carbon.
He's been doing these things for a long time and as I mentioned is part of the car racing mechanical group who get involved in some of the biggest racing teams in the country, so he's well into identifying weird problems and he agrees with me now he's got deeper into it and reckone he's never struck anything like it before, so trust the French.


Alan S

[Jaba]

I used to have a TZi with a cat. It too burnt huge amounts of oil without any sign of blue smoke. The engine had done around 100k miles. As far as I recall it burnt about 1L per 500 miles. The engine was VERY noisy at speed too.

I decided to deal with it.

Fitted new big end bearings, piston rings - forget what type were fitted or replaced with.The valve stem seals only were replaced as I could not be bothered at the time to have the valves or their guides looked at. I knew it was a considered gamble.

The result was BX perfection. No oil was burnt between changes. There was no engine noise audible at speed, unlike before. Sadly an octagenarian driver wrote the car off with wife at the wheel at a T junction 12 months later.
I rescued the aircon and engine ECU from it after accepting the third party's insurance offer.

[AlanS]

A bit of an update;
I've got the engine all back together but minus the head as I had to wait for it to come back from the machine shop and I'm not about to rush for the sake of a day or two. At A$570 trade price, it sounds as though it should be a pearl when we get it back the way he's talking and the reutation this guy has got.

When refitting the sleeves and pistons etc, I found that as well as having the far better design with the oil rings, there was also a difference with the compression rings also.
The originals were the outer stepped variety which means only about 75% of the ring face makes contact with the cylinder wall due to the step in the outer part of the ring, whereas the new ones are bevelled on the inner edge and have to be set with the bevel to the top. This is a varience on an idea the Japs flogged back in the '60s when Toyota Coronas and Datsun Bluebirds were the dominant makes and models amongst the Jap stuff. They referred to them as "Umbrella" rings and were designed to use a bit of oil for the first 500 - 1000 miles at which point the slight flexing of the rings as they moved up and down supposedly rounded the edges off fractionally and caused them to seal mre effectively. We'll soon know if that's the case here.
Tommorrow we refit the flywheel, clutch and gearbox as well as some of the wiring harness we stripped out to redo whilst it was apart. The new octopus will also be on the agenda and hopefully I'll get time to do the PR. FD and other accessories over while we wait for the head.
Looks like next weekend is engine back day.


Alan S

[jeremy]

Alan

Is that original top ring a ridge dodger? The reason I ask is that if the step in the old ring is at the top outer edge then the wear ridge at the top of the bore may cause problems with new rings that do not have the cut-out. I know that wet liners won't wear like a BMC A series engine but there'll probably still be some ridge there which could cause problems.

Long term reliability was something that never seemed to trouble British engineers - and so many innovations by the Japanese are good even if the overall car concept may seem strange. Someone explained the difference of approach like this: Ask an operative to cut a gear to a certain tolerance - and he'll produce them within that limit. Ask a Japanese to do the same job and they'll all be within tolerance and after a short while they'll all be spot on without the variation - which probably explains why their stuff lasts for ever.

[AlanS]

The liners had a ridge cutter run over them and all liners were honed, so ridge is a non event.
I could understand to a point having a ring with an outer cut out being fitted to a worn motor to allow for a ridge but not to a new one to make one; it's crazy.
Normally it's the Japs that copy and the French that innovate so it appears when they change roles it doesn't work so well.

You must get different Jap cars to us if yours don't wear out.
We've put a Mazda back in service as a runabout while the BX is off the road and the son who owns the BX has suddenly developed a serious case of enthusiasm to get it back after driving Jap for almost 6 months and putting up with the constant string of niggles, and without trying to go O/T I used to manage one of the largest Toyota franchises in the State and believe me, Jap reliability is more in the way that they handle complaints than in the way they build their cars.
The Mazda BTW was gone through from stem to stern by a Jap car specialist and this included a rebuilt engine at 235K klms. I've bought French cars with more than that on the clock and considered that low mileage.
Some of the Jap stuff has also been notorious for oil consumption and with their laws regarding "shelf life" and emissions, some of their cars from the past have had built in obselesence based on their reasoning that there was no point in making a car that lasted beyond around 100K klmsas it wouldn't be capable of being re-registered past that anyway, so perhaps Froggy read the book incorrectly.


Alan S