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BMC 1.5 smoking at higher revs


David Mutch
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32 minutes ago, David Mutch said:

I've always wondered with one that runs off the alternator whether they have to be calibrated somehow, as I'd have thought it depends on the pulley ratios to a great extent?

 

Yes. You need a way of measuring the engine speed (handheld tacho is easiest) then usually rev the engine to a specific RPM and press a SET button/switch.

 

There should be instructions with the unit.

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5 hours ago, Tony Brooks said:

The only reason for a lower temperature thermostat on a tank, keel or heat exchanger boat is to reduce the maximum domestic hot water temperature. No reason not to fit an 88C one and if it proves dangerous (scalding) fit a thermostatic mixing valve if you don't already have one.

 

If the noise is diesel knock you would expect it to reduce with a higher engine temperature because the delay period would be shorter so less unburned fuel igniting at once, so a lower pressure pulse.

I've no idea why the OP is going to change the thermostat, might as well change the gearbox! 

 

It reminds me of a very interesting fault with a Perkins in a small fishing boat that was in the very next berth to me in Peurto Mogan. The engine did not start or run correctly until warm, BUT every wanabee diesel engine expert in the area had tried to figure out why since he purchased the boat, and failed with spectacular success. I had no clue, so arranged for an old friend and real serious expert to take a look for free, and it only took him about half an hour to find out that the injection timing was wrong. Lots of wanabee experts had fiddled with the timing but only he noticed that the pulley was not OEM, but had been replaced for some reason by a previous owner, and that particular expert had failed to look at the various diagrams of the pulley and where the timing mark was. So my old friend just ignored the mark and figured out the correct angle by checking the position of the cylinders. That Perkins then started just as well as a new diesel on a warm day. 

  So the moral of the tale is that until the OP gets a real good diesel engineer to inspect his engine, it's not going to purr like a BMC should, in fact things might get far worse if it's a bad HG or something serious coming adrift inside the block, then it might go bang and have to be put down to avoid any further suffering. Yep, another avoidable scrap yard breaking a real classic diesel for spares!

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6 hours ago, TNLI said:
11 hours ago, Tony Brooks said:

 

I've no idea why the OP is going to change the thermostat, might as well change the gearbox! 

 

That is because you have not followed the topic in enough detail or simply don't or can't understand it. The OP's decision to change the thermostat has nothing or very little to do with the smoke. It is because he observed that the engine was less noisy when really hot. I explained what that might be and why cooler thermostats are fitted to some tank/keel/heat exchanger cooled engines. The OP decided that it is worth changing the thermostat. It is all perfectly logical if you follow the thread and understand what each post is about. The misunderstanding is made far more likely when people insist on resurrecting zombie threads and on current threads post only tangentially related posts.

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3 hours ago, john.k said:

Valve stem seals (and valve springs) are easily replaced without removing the head.....the full set of seals would take maybe 1/2 hour to replace at most.

Interesting polite post, as I did not know that job could be done without removing the head. I posted a link the a series of you tub clips on the engine rebuild title today, so if anyone needs to change them, it's probably in the third clip.

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4 hours ago, john.k said:

Valve stem seals (and valve springs) are easily replaced without removing the head.....the full set of seals would take maybe 1/2 hour to replace at most.

 

But it does need  a suitable spring compressor because I fear trying the two man, ring spanner and pin nosed pliers method  could all too easily push the piston down the bore so you risk dropping the valve into the cylinder.

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With piston at TDC ,its geometrically impossible to rotate the crank by pushing down on the piston......Ive always done the cap and cotter removal by myself ...a simple tap on a deep socket will remove cap and collets............the process reversed to replace the cap and collets by simply pressing down 

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15 minutes ago, john.k said:

With piston at TDC ,its geometrically impossible to rotate the crank by pushing down on the piston......Ive always done the cap and cotter removal by myself ...a simple tap on a deep socket will remove cap and collets............the process reversed to replace the cap and collets by simply pressing down 

 

Agreed, if it really is at TDC  and relying on the valves to give that is no guarantee of accuracy.

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18 hours ago, TheBiscuits said:

 

Yes. You need a way of measuring the engine speed (handheld tacho is easiest) then usually rev the engine to a specific RPM and press a SET button/switch.

 

There should be instructions with the unit.

 

@TheBiscuitsThanks (although needing a rev counter to calibrate a rev counter seems a bit of a catch 22 to me!)

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23 minutes ago, David Mutch said:

 

@TheBiscuitsThanks (although needing a rev counter to calibrate a rev counter seems a bit of a catch 22 to me!)

There is no need to use a rev counter or timing strobe if you don't have one, just read the instructions, then paint a mark on the main crank pulley and film the engine at a stable idle with your phone, then once it's uploaded use a rev check program, or simply slow down the clip and count the number of turns. A few simple sums will give you an idea if your new RPM gauge is correct, or needs adjusting.

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17 hours ago, TNLI said:

I've no idea why the OP is going to change the thermostat, might as well change the gearbox! 

 

It reminds me of a very interesting fault with a Perkins in a small fishing boat that was in the very next berth to me in Peurto Mogan. The engine did not start or run correctly until warm, BUT every wanabee diesel engine expert in the area had tried to figure out why since he purchased the boat, and failed with spectacular success. I had no clue, so arranged for an old friend and real serious expert to take a look for free, and it only took him about half an hour to find out that the injection timing was wrong. Lots of wanabee experts had fiddled with the timing but only he noticed that the pulley was not OEM, but had been replaced for some reason by a previous owner, and that particular expert had failed to look at the various diagrams of the pulley and where the timing mark was. So my old friend just ignored the mark and figured out the correct angle by checking the position of the cylinders. That Perkins then started just as well as a new diesel on a warm day. 

  So the moral of the tale is that until the OP gets a real good diesel engineer to inspect his engine, it's not going to purr like a BMC should, in fact things might get far worse if it's a bad HG or something serious coming adrift inside the block, then it might go bang and have to be put down to avoid any further suffering. Yep, another avoidable scrap yard breaking a real classic diesel for spares!

Unfortunately, not all of us have have access to such good advice, especially for free. I suspect that's why a lot of folks come here looking for counsel. Indeed, my experience has tended to be that even if willing and able to pay, it's very hard to find a mechanic that good, especially when it comes to diagnosing something at all out of the ordinary. That's pretty much why I have learned as much as I have about engines and do as much of my own work as I can. If you can recommend someone on the Kennet and Avon with those kinds of skills, I'm all ears.

 

I think it's a little unfair to say that I might as well change the gearbox, but perhaps I've not been 100% clear in articulating my reasoning. As @Tony Brooks points out, there did seem to be some improvement in engine sound when hot. However, that's not all. I have always believed that the stat is unnecessarily cool (I believe it's a 74 or even 72 degree stat). I'd never thought about cooler stats being used to regulate domestic hot water temperature, but I have heard they're often used in engines that have raw water cooling, especially if used in brackish or sea water, as this helps reduce corrosion, but that it's a bit of a trade off in terms of engine life, as running cool can cause other problems. I believe my engine may have been converted from raw water to a skin tank at some point in its life, so perhaps that's why it has a cooler stat. My current working hypothesis is that the smoke is due to prolonged periods where the engine is under insufficient load, just generating electricity, (especially over the last two years of working from home) and doing the occasional cruise with few locks and no flow requiring high power or rapid deceleration. I think this may have caused a buildup of a combination of carbon, diesel and oil (and perhaps even water, as the exhaust could conceivably collect condensation or rain water), causing smoke under higher revs, where there's more air flow through the engine to blow the gunk out, and increased exhaust temperature to help vaporise it. I'd reason that such a buildup is less likely to occur if any stray oil or diesel is ejected from the engine at a higher temperature in the first place, and that a higher temperature in the rings is likely to lead to expansion and therefore less oil and unburned diesel in the cylinders and therefore the exhaust system. Perhaps I'm wrong, but I guess I'll find out when I change the stat :)

10 minutes ago, TheBiscuits said:

 

I did say it was the easiest way ...

 

One of our members did it with a guitar tuner app and some mathematics!

 

 

I like the cut of their jib!

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20 minutes ago, TNLI said:

There is no need to use a rev counter or timing strobe if you don't have one, just read the instructions, then paint a mark on the main crank pulley and film the engine at a stable idle with your phone, then once it's uploaded use a rev check program, or simply slow down the clip and count the number of turns. A few simple sums will give you an idea if your new RPM gauge is correct, or needs adjusting.

Thanks. I'd never have thought to get that inventive!

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I understand you can get a strobe rev counter app for mobile phones so you don't need to do any counting or maths. Also buried on the forum somewhere are instructions on how to use a cheap electronic bicycle speedo as a revcounter.

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Just now, Tony Brooks said:

I understand you can get a strobe rev counter app for mobile phones so you don't need to do any counting or maths. Also buried on the forum somewhere are instructions on how to use a cheap electronic bicycle speedo as a revcounter.

These modern marvels never cease to amaze!

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58 minutes ago, David Mutch said:

These modern marvels never cease to amaze!

 

I insist it's still easiest with a £20 handheld tachometer and a blob of tippex!

 

If you're fitting a £100 tacho it's worth doing, or simply beg borrow or steal one off a boat engineer.

 

59 minutes ago, Tony Brooks said:

I understand you can get a strobe rev counter app for mobile phones

 

Ooh. That would be better.  Do you know what the app is called please?

 

I'll get it!

 

 

 

Edited by TheBiscuits
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2 minutes ago, TheBiscuits said:

 

I insist it's still easiest with a £20 handheld tachometer and a blob of tippex!

 

If you're fitting a £100 tacho it's worth doing, or simply beg borrow or steal one of a boat engineer.

 

 

Ooh. That would be better.  Do you know what the app is called please?

 

I'll get it!

 

No, I read about it on here. I don't have a smart phone.

 

Here you go; https://play.google.com/store/apps/details?id=jp.nas.giri&hl=en_GB&gl=US

I am sure Apple has something similar.

Edited by Tony Brooks
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5 hours ago, TheBiscuits said:

 

I insist it's still easiest with a £20 handheld tachometer and a blob of tippex!

 

If you're fitting a £100 tacho it's worth doing, or simply beg borrow or steal one off a boat engineer.

 

 

Ooh. That would be better.  Do you know what the app is called please?

 

I'll get it!

 

 

 

WTF would any BMC owner fit a 100 quid tacho, or RPM gauge, when a universal one only costs about 25 quid from Fleabay, even if you buy the real McCoy from ASAP, they cost less than 50 quid including VAT and shipping. I try not to suggest anything too expensive to boat owners who have an odd habit of feeding their BMC donkey junk oil just to save a few quid. 

 

PS: You can buy electronic rev counters that do not need calibrating, but they are more expensive, or iyou can buy a black box sensor to fit near the alternator that senses how fast it's going: 

Diesel Engine RPM Tacho Sensor UNIVERSAL For Vehicle Truck Boat Yacht Waterpoof | eBay

Or even a normal sensor, if you can find or tap a 16mm hole:

Diesel Engine M16 Tachometer Sensor Tacho Gauge RPM Sender for Car Truck Yacht | eBay

Finally, you can also fit a sensor near the cam shaft, and they do not need a big hole:

Camshaft position sensor - function & troubleshooting | HELLA

Note that Hella also make cam shaft position sensors that allow you to check the timing. They are often used by engineers working on engines with a LASAR, (Limited authority spark advance regulator), or the much more common VVT, (Variable valve timing), systems found on many smallish petrol engines, including a Renault Twingo 1.2 classic with a roll back roof, that I abandoned to the care of my daughter in Germany. One cool town car!

Edited by TNLI
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1 minute ago, TNLI said:

WTF would any BMC owner fit a 100 quid tacho, or RPM gauge, when a universal one only costs about 25 quid from Fleabay, even if you buy the real McCoy from ASAP, they cost less than 50 quid including VAT and shipping. 

 

Don't Liquid Molly  do an additive you can pour into your engine to set the new rev counter?

 

Maybe you should look into it ...

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So, went for our first cruise today since all the tinkering. 

 

Before doing so, I put the pump timing back to dead on the mark and replaced one of the pipes between the fuel filter and the injector pump, which was probably 30 year old copper, and didn't take kindly to being disturbed twice in one week.

 

After a short warm up, I gave it some beans in neutral. Got a fair bit of smoke to begin with, but perhaps not as much as before, and this time it started to clear within 30 seconds or so, even without putting a lot of heat in the engine as previously.

 

Set off, and wherever possible, opened up the taps. No smoke! Or none to speak of. The engine was also running noticeably smoother and quieter (the OH commented on this completely unprompted, so I don't think I was imagining it!).

 

There's still one thing that I thought worth consulting the hive mind about. I wonder whether my symptoms could possibly be explained by a sticky oil pressure relief valve. I've not really had an eye on the oil pressure before when it's been billowing smoke, but I noticed today that when I first gave it some revs, the oil pressure shot up to nearly 100psi. I might have expected something like that with a stone cold engine, but I'd already run the engine for a while in the morning, so it wasn't completely cold. When giving it some welly on the cruise, it peaked at maybe 80psi, which seems more normal, although admittedly I probably didn't reach quite the same rpm, and that still seems higher than my previous BMC (although that could just be down to a different gauge to some extent, I suppose.) Could excessive oil pressure be forcing oil past the rings at high revs, perhaps? And could getting some heat/oil pressure in the engine help un-stick the valve, or just reduce the oil pressure enough due to higher oil temp, that the smoke subsides?

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If it drops very low on hot idle (Say 15psi) then yes because a sticky PRV usually jambs open. My money would be on a faulty sender unless its a mechanical gauge.

 

Personally  can't see  excess oil pressure blowing oil past the pistons, I can't remember if the 1.5 has oil jets in the big ends to squirt oil onto the thrust face but even if it does doubt it would cause the oil to get past decent oil control rings.

 

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24 minutes ago, Tony Brooks said:

If it drops very low on hot idle (Say 15psi) then yes because a sticky PRV usually jambs open. My money would be on a faulty sender unless its a mechanical gauge.

 

Personally  can't see  excess oil pressure blowing oil past the pistons, I can't remember if the 1.5 has oil jets in the big ends to squirt oil onto the thrust face but even if it does doubt it would cause the oil to get past decent oil control rings.

 

Thanks Tony. It usually never goes below 50psi, except the other day when I revved it for a long time and it dropped to 35ish afterwards, then climbed back up slowly, but I put that down to a lot of heat causing the oil to thin. The gauge and sender are new (well in the last 2 years or so), although I realise that doesn't guarantee working correctly. By and large its readings seem consistent with what I'd expect, but I've usually been too preoccupied with the smoke before now to pay attention to the gauge when I've got the hammer down, and the readings I saw today seemed on the high side. The fact there was zero smoke today on my cruise, plus good compression readings, makes it seem unlikely to me that the rings are bad. I guess the gunged up exhaust theory is still the most likely, but perhaps I'll investigate the relief valve anyway, as I've never had it out.

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1 hour ago, David Mutch said:

Thanks Tony. It usually never goes below 50psi, except the other day when I revved it for a long time and it dropped to 35ish afterwards, then climbed back up slowly, but I put that down to a lot of heat causing the oil to thin. The gauge and sender are new (well in the last 2 years or so), although I realise that doesn't guarantee working correctly. By and large its readings seem consistent with what I'd expect, but I've usually been too preoccupied with the smoke before now to pay attention to the gauge when I've got the hammer down, and the readings I saw today seemed on the high side. The fact there was zero smoke today on my cruise, plus good compression readings, makes it seem unlikely to me that the rings are bad. I guess the gunged up exhaust theory is still the most likely, but perhaps I'll investigate the relief valve anyway, as I've never had it out.

Before you start doing something expensive like pulling the engine apart, I would try a can of this very effective pre oil change flush additive from Liquid Moly, although if you are a Castrol fan, they also make a very similar product listed in their classic car section:

Liqui Moly Pro-Line Engine Flush 2427 - 500ml | Additives | Accessories | Battery Group

Product data sheet:

P003601-Engine Flush Plus-15-en (liqui-moly.de)

 

Castrol version:

Castrol Engine Shampoo (Pre-Oil Change Treatment) 300ml (opieoils.co.uk)

Product data sheet:

BPXE-BL4K8F.pdf (opieoils.co.uk)

 

I'm kind of wondering if your oil pressure gauge is not faulty, due to a blocked sensor pipe if it's a real old pipe job, or an Iffy electrical connection if it's a more common gauge type, that you have got some sludge or varnish deposits around the block, and although the BMC is not regarded as a sludge monster, that does not mean you do not have some blocked up oil flow pattern issues, and that can result in an erratic oil pressure. 

  The main reason for sludge formation results from using poor quality engine oil that lacks detergent additives, (Low TBN number in the data sheet), or using a good major brand oil for far too long a period. Varnish is different, as although cheap oil will be more prone to its formation, such deposits tend to be much worse if the engine is running too hot for some reason like a clogged up heat exchanger. Varnish deposits tend to form where there is air present, so they don't block up the oil pump intake screen like sludge can. A major brand pre oil change flush additive will dissolve both sludge and varnish from the block.

Edited by TNLI
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