Surprisingly the manifold nuts all came off as they should this time and left all eight studs in the head... weird, but it certainly made fitting the gaskets a lot easier.
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Showing posts with label m10b18. Show all posts
Showing posts with label m10b18. Show all posts
Saturday, 16 February 2013
E21 316: More manifold gaskets for M10...
Stuck the new and much better quality exhaust-manifold gaskets on today from Euro Car Parts. They're thicker than the eBay ones and have steel rings round the inner rim like a head-gasket, should make a better seal. It's got rid of the cracking noise from that dodgy one on cyl. 4 [this post] and the engine sounds sweeter than ever.
Surprisingly the manifold nuts all came off as they should this time and left all eight studs in the head... weird, but it certainly made fitting the gaskets a lot easier.
Surprisingly the manifold nuts all came off as they should this time and left all eight studs in the head... weird, but it certainly made fitting the gaskets a lot easier.
Sunday, 10 February 2013
E21 316: M10 Engine cured! - Culprit: manifold gasket...
After repeatedly timing the ignition perfectly to Z on the flywheel, [see this post], we decided there had to be something deftly wrong to be causing the loud noise and backfiring [in the vid below], rather than just the distributor being out of line.
The first hunch was the exhaust had broken while being twisted to get the cylinder-head out and was blowing like mad, but my initial inspections revealed no damage to the down-pipe or manifold and the four manifold gaskets looked all to be in position.
That is to say they LOOKED in position... Today, in the pouring rain, I got the car up on ramps to see what it was I'd missed and as soon as the torch flicked on I could see the answer at last - one of the exhaust-manifold gaskets had slipped off the stud and was only covering half the hole! Nightmare... Right at the back of the engine where we couldn't see and, ironically, the one for cylinder 4 that started all the trouble.
As you can see the gasket has been totally blown apart by the hot exhaust and has separated quite badly in the middle leaving only the metal. I checked the rest of the gaskets in my set for a spare, but can only find the same shape gasket with an oblong hole, perhaps for the E28, so tentatively decided to re-use the blasted one, correctly seated this time and caked in Holt's FireGum.
As soon as the engine fired up again it sounded like it used to. It's amazing the difference that gap in one single exhaust port made to the noise level. It was still idling low though and revving badly, so I grabbed the timing-light again to have another go, turning the distributor to line up Z on the flywheel - 25 degrees before TDC. Now the 30 year old M10 has really begun to purr once more. Awesome! Still some fettling to do on the carb. tuning, throttle/choke cables and checking to see if my damaged manifold-gasket is holding up, but at least she's back on the road after a tense month!
The first hunch was the exhaust had broken while being twisted to get the cylinder-head out and was blowing like mad, but my initial inspections revealed no damage to the down-pipe or manifold and the four manifold gaskets looked all to be in position.
That is to say they LOOKED in position... Today, in the pouring rain, I got the car up on ramps to see what it was I'd missed and as soon as the torch flicked on I could see the answer at last - one of the exhaust-manifold gaskets had slipped off the stud and was only covering half the hole! Nightmare... Right at the back of the engine where we couldn't see and, ironically, the one for cylinder 4 that started all the trouble.
As you can see the gasket has been totally blown apart by the hot exhaust and has separated quite badly in the middle leaving only the metal. I checked the rest of the gaskets in my set for a spare, but can only find the same shape gasket with an oblong hole, perhaps for the E28, so tentatively decided to re-use the blasted one, correctly seated this time and caked in Holt's FireGum.
As soon as the engine fired up again it sounded like it used to. It's amazing the difference that gap in one single exhaust port made to the noise level. It was still idling low though and revving badly, so I grabbed the timing-light again to have another go, turning the distributor to line up Z on the flywheel - 25 degrees before TDC. Now the 30 year old M10 has really begun to purr once more. Awesome! Still some fettling to do on the carb. tuning, throttle/choke cables and checking to see if my damaged manifold-gasket is holding up, but at least she's back on the road after a tense month!
Sunday, 3 February 2013
E21 316: M10 Distributor/Ignition Timing: Strobe Light Ahoy!
So my adventures into re-timing the spark-plugs continue with the purchase of a Gunson Xenon timing strobe-light! I went for the cheapest kit in Halfords, but it was still a slight pain at £45, considering it's in addition to a new dizzy-cap and rotor-arm, set of spark-plugs, compression-test kit, gasket-set, oil, coolant and a 30mm socket to turn the engine from the crank, but as I just can't seem to get the old M10 engine running happily I guess it's just as vital and at least we can use it to time in our old MGA engine this summer (hopefully).
Before I start to moan again about the intricacies of re-timing the distributor I should say that I know there is no need to remove it in order to get the cylinder-head off and the dizzy should really be left in place to save all this trouble, but the diaphragm on mine was blocking one of the head-bolts so that wasn't an option for me.
The timing light works by flashing every time your 1st-cylinder spark-plug fires. There is a timing-mark on the spinning crank-pulley or flywheel that passes a stationary mark on the block at the exact point the 1st spark-plug should be firing. When the flashing light from plug 1 is aimed at the spinning pulley it shows the timing-mark in a fixed position in relation to the stationary mark and allows you to gauge how how many degrees before or after the correct point the spark is. Clever stuff.
On the BMW M10 engine, there are two timing-marks on the flywheel, one for top dead-centre [TDC] and another, called Z, that corresponds to the right point before TDC that the 1st spark-plug should be firing. The marks are visible with the flashing light through a small oblong hole at the back of the crankcase. It's easy enough to find the hole, but seeing into it with the timing-light is a challenge in itself, let alone trying to adjust it or move the dizzy-cap and I ended up having to stand over it with my feet on the strut-tops to steady myself enough without leaning in from the side and crushing the wheel arches. There is another TDC timing-mark on the rearmost rim of the front crank-pulley, which is a lot easier to see with the timing-strobe from the n/s of the engine-bay, but the mark is tiny so when you do find it it's best to file a larger notch across the whole pulley - mine had this done already and it makes things a lot clearer.
It's best to first time your engine to Z on the flywheel, at 2200rpm, using 0 degrees of advance on the timing-light gun - just shine it into the oblong hole and rotate the distributor-cap until the large pointer is lined up with the silver ball, not the TDC line. Now check the front crank-pulley for reference by shining the light at it with 0 degrees advance. The groove for TDC should appear around 25 degrees before the stud on the engine-block. Rotate the dial on the timing gun slowly to 25 degrees and the groove should move in line with the pin. Simples.
Ignition timing isn't too much of a fine art, so as long as the rotor-arm contact is roughly on point no.1 on the dizzy with the engine at top dead-centre then it should fire right up and not need much adjustment to find Z. Mine was still making the god awful noise after repeatedly timing to Z, but this turned out to be a badly positioned exhaust-manifold gasket [in this post] so, obviously, check everything else isn't amiss before starting to mess with ignition timing.
Before I start to moan again about the intricacies of re-timing the distributor I should say that I know there is no need to remove it in order to get the cylinder-head off and the dizzy should really be left in place to save all this trouble, but the diaphragm on mine was blocking one of the head-bolts so that wasn't an option for me.
The timing light works by flashing every time your 1st-cylinder spark-plug fires. There is a timing-mark on the spinning crank-pulley or flywheel that passes a stationary mark on the block at the exact point the 1st spark-plug should be firing. When the flashing light from plug 1 is aimed at the spinning pulley it shows the timing-mark in a fixed position in relation to the stationary mark and allows you to gauge how how many degrees before or after the correct point the spark is. Clever stuff.
On the BMW M10 engine, there are two timing-marks on the flywheel, one for top dead-centre [TDC] and another, called Z, that corresponds to the right point before TDC that the 1st spark-plug should be firing. The marks are visible with the flashing light through a small oblong hole at the back of the crankcase. It's easy enough to find the hole, but seeing into it with the timing-light is a challenge in itself, let alone trying to adjust it or move the dizzy-cap and I ended up having to stand over it with my feet on the strut-tops to steady myself enough without leaning in from the side and crushing the wheel arches. There is another TDC timing-mark on the rearmost rim of the front crank-pulley, which is a lot easier to see with the timing-strobe from the n/s of the engine-bay, but the mark is tiny so when you do find it it's best to file a larger notch across the whole pulley - mine had this done already and it makes things a lot clearer.
It's best to first time your engine to Z on the flywheel, at 2200rpm, using 0 degrees of advance on the timing-light gun - just shine it into the oblong hole and rotate the distributor-cap until the large pointer is lined up with the silver ball, not the TDC line. Now check the front crank-pulley for reference by shining the light at it with 0 degrees advance. The groove for TDC should appear around 25 degrees before the stud on the engine-block. Rotate the dial on the timing gun slowly to 25 degrees and the groove should move in line with the pin. Simples.
Ignition timing isn't too much of a fine art, so as long as the rotor-arm contact is roughly on point no.1 on the dizzy with the engine at top dead-centre then it should fire right up and not need much adjustment to find Z. Mine was still making the god awful noise after repeatedly timing to Z, but this turned out to be a badly positioned exhaust-manifold gasket [in this post] so, obviously, check everything else isn't amiss before starting to mess with ignition timing.
Monday, 14 January 2013
E21 316: M10 Misfire Woes:
Went on a Maccies run with some work colleagues on New Year's Eve and I may have been pushing the old girl a bit hard, when a horrible clanging noise began from the engine and got worse quickly. Some of the guys at work suggested the first stop should be the rotor-arm and dizzy-cap so we managed to get some delivered through the parts dept. that afternoon, but it was still chugging on a mixture of cylinders and it limped home for me then refused to start again. When it eventually did the old M10 barely managed to fire 3 cylinders.
My list of diagnostic checks was:
Replaced distributor-cap and rotor-arm.
Tested all 4 plug-leads.
Replaced all 4 spark-plugs.
Removed, cleaned and rebuilt Weber carb.
Checked valve-clearances and confirmed all valves appear to be moving correctly, turning the engine by hand.
Finally diagnosed cylinder 4 as no firing.
Plug and lead tested again, this time sparking against the suspension turret.
Compression test revealed Cyl. 1 and 2 @ 150psi, 3 @ 45psi and 4 @ 25psi.
This all seems to point to a bust head-gasket between the 3 and 4 cylinders. It is unlikely the valves for 2 cylinders would have bent or suddenly need adjusting at the same time, so off with its head and lets look at that gasket.
*UPDATE: The head came off pretty quickly and revealed one seriously blown head-gasket right between the 3rd and 4th cylinders [detailed pics in this post]. Diagnosis spot on, but the culprit may be a slight warping at that end of the alloy-head - not very much at all, but still a worry considering it looks to have been skimmed before. Either way, the new head-gasket is on [I went for a full head set off eBay for £27.99, which includes the manifold gaskets etc.] and the car is running on all four cylinders again, though not as happily as it could be. I was forced to remove the distributor and seem to be having some issues with ignition timing since putting it back [in this post], and the carb. still hasn't been tuned properly since the rebuild, so a range of fettling awaits before I can drive it for the first time in 2013.
My list of diagnostic checks was:
Replaced distributor-cap and rotor-arm.
Tested all 4 plug-leads.
Replaced all 4 spark-plugs.
Removed, cleaned and rebuilt Weber carb.
Checked valve-clearances and confirmed all valves appear to be moving correctly, turning the engine by hand.
Finally diagnosed cylinder 4 as no firing.
Plug and lead tested again, this time sparking against the suspension turret.
Compression test revealed Cyl. 1 and 2 @ 150psi, 3 @ 45psi and 4 @ 25psi.
This all seems to point to a bust head-gasket between the 3 and 4 cylinders. It is unlikely the valves for 2 cylinders would have bent or suddenly need adjusting at the same time, so off with its head and lets look at that gasket.
*UPDATE: The head came off pretty quickly and revealed one seriously blown head-gasket right between the 3rd and 4th cylinders [detailed pics in this post]. Diagnosis spot on, but the culprit may be a slight warping at that end of the alloy-head - not very much at all, but still a worry considering it looks to have been skimmed before. Either way, the new head-gasket is on [I went for a full head set off eBay for £27.99, which includes the manifold gaskets etc.] and the car is running on all four cylinders again, though not as happily as it could be. I was forced to remove the distributor and seem to be having some issues with ignition timing since putting it back [in this post], and the carb. still hasn't been tuned properly since the rebuild, so a range of fettling awaits before I can drive it for the first time in 2013.
Sunday, 13 January 2013
E21 316: Head Gasket - well and truly blown!
Here are some pics of the blown head-gasket that turned out to be the misfire culprit [from this post: ] and it turned out my forum-eductaed guess was right and it had failed right between the 3rd and 4th cylinders. Kaboom!
No damage to the water/oil galleries thankfully, but still a catastrophic way for the gasket to fail so quickly under a bit of load. You can see best in the bottom pic of the head where the gasket has begun to fail at the left side of cylinder 4, taking that down and then blowing through to cyl. 3. Not good. An examination of the cylinder-head when removed showed that it is warped a tiny bit, so it looks like the engine has been overheated at some point before I got the car and this is probably going to happen again. Oh well, priest-like driving will be the order of the day unless I just go seat-of-the-pants until it goes again, but in the long-term, an M44 engine-swap from a more modern 318is is looking like a must!
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