Top end rattles/oil pressure loss on 16V engine

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alan s
RIP 2010
Posts: 2542
Joined: 26 Jan 2001, 15:53
Location: Australia
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Top end rattles/oil pressure loss on 16V engine

Post by alan s »

As many know, a while back my son did a rebuild on the BX 16V series one (160 BHP) engine. Everything was done by the book & only the best of the best went into that engine & only very competant tradepeople worked on or oversaw what was done. It should have been as close to perfect it was humanly possible to get!!
On completion, it was even given an initial run on "running in" oil followed by a full synthetic which was changed at around 1500 klms; you don't get any keener or careful than that do you?
However; whilst it performed up to expectations, it never sounded right; it clattered similar to a sewing machine on start up and when it heated up, whilst the noise lessened, so did the oil pressure. It was 'top end' noise but where?? Couldn't be the hydraulic tappets; they're self adjusting.....right??!!
Problems with cam lobes?? Doubt it.
Bearings on the camshaft?? They checked out OK when the engine was down.
Oil pump? That's gotta be it.....bet the pump's worn out inside and it won't pump oil throughout the circuit and it starves the top end when cold & just simply doesn't pick it up properly when hot. Interesting theory but what a bugger to inspect....put that one down as a last resort job.
We'll try a heavier oil & see what happens....no difference, and so it went on!
Last week in desperation & showing all the signs of mega frustration, I go to the garage to find he's got the top end of the engine all over the bench; cover off, cams out, cambelt off, sprockets off the end on the cams, oil supply pipes out and asking questions about oil circuits. Is there a blockage? Is there a seal of some description that's blown? It couldn't possibly be the hydraulic tappets could it? After all, they self adjust but if I were a betting man I'ds reckon they were it but there's nothing there that can cause the rattle; they're too basic!!
Get online looking for oil circuits, pumps, specs etc and everything is checked out; it's nothing but a bloody mystery that we'll just have to live with but out of curiosity, it'd be nice to find it. "Give Jon Wood a call at Andyspares & get a price on new hydraulic tappets; but I can't see them being the problem!"
Jon comes back with a price of 14 UK pounds, or about A$35 each. That works out at about A$560 BEFORE we ad freight, import duties, GST etc so possibly the price of a meat pie out of $900 - $1000 and we still have doubts about these being the cause. We ask Jon's opinion which was he didn't think these things ever wore out; our thoughts exactly. He also sent a section of the parts manual of the parts he was referring to and........GULP!!! That was only for the outside bit, but didn't include the small pistons inside, so we didn't even ask about the price...scarey stuff!!
Bugger it says Brad, we've got that other motor there, let's pull the guts out of the top end of that & swap just for the hell of it. Off comes cover, cams, belt etc, etc, etc....and out comes the valve lifters. Try one besides the other & where one was nice & springy, the ones out of the cars engine were 'dead' feeling; not so much difference when both filled with oil, but once drained, a completely different feel.
The cars engine internally was pretty sludgy when it was initially pulled down and we had suspicions it was a typical UK BX; only had oil changes at the intervals as advised by Citroen which I've long maintained were more of an advertising ploy and assisting with the obscelesence than they were for the longeivity of the car & it's engine, so as a result, it would seem that the varnish & sludge that circulates around in engines that go 20K and the like between oil changes, finds its way onto the walls of the small piston & cylinder within the actual hydraulic lifters & proceeds to simply grind them away. As a reslt, the small piston (acting like a piston should) builds up a pressure with the oil to cushion the lifting of the valve. When they wear, this piston then slides straight to the bottom of this small cylinder with little or no oil resistence & simply bottoms out leaving a bright shiny circular mark that can be seen inside the base of teh small cylinder mounted within the large one.
Reassembled, it now purrs like a kitten.
Thought I'd put all this together while it was still fresh in my mind to save anyone else the frustration we've had and also as a warning to anyone getting a motor redone as we often see people with things like slight misses trying to convince themselves it's the ECU when in fact it can be a short in a lead. This is a similar thing; no way could we believe it was something this obvious.
It should also act as a warning to anyone wanting to try to get a few extra miles between oil changes and or using cheaper oils.
We got out of it fairly cheaply due to our ability to DIY & our resources on hand; the mind boggles at what an owner could be charged at one of our service outlets with a $110 charge out rate & a habit of charging double price for parts.
Alan S
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