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Post by enigmas on Jan 14, 2018 9:21:34 GMT
Just prior to Christmas my wife and I gifted our youngest daughter our reliable and well maintained little runabout, a 1998 1.5 litre Mitsubishi Lancer coupe, (5 speed manual, alloy sport wheels, EFI, power rack & pinion steering and A/C) with the aim of reducing the toll that daily use was taking on her Classic 1966 XT Ford Falcon. Unfortunately Murphy's Law intervened unexpectedly, the car developed a weeping radiator, the coolant levels dropped...and before you could say seized engine, the little car halted in a cloud of steam on a freeway in the care of my eldest daughter. I imagine that the dash lights may well have lit up like a Christmas tree prior to the inevitable, but sometimes it's better to leave 'sleeping dogs' lie and just apportion it to fate. Both girls were quite upset..so it was easier to move on rather than dissect what occurred. Briefly, during a high speed run along a freeway the engine purged most of it's coolant and then cutout. The spark plug boots virtually melted due to the heat. Fortunately the car had been very well cared for before the incident. The engine didn't seize but the head gasket is blown and the cyl head has to come off. Water did enter the cyls pressurizing the radiator and blowing the top tank seal. The radiator has a plastic top tank affixed to an alloy core. This also requires replacement. The 4 cyl engine is 12 valve, OHC and belt driven from the crankshaft. There's quite a lot of dismantling required to remove the head. I took a compression reading before removing the head. It read and sounded a very asthmatic 30 psi on all cylinders...obviously too low to fire up! PART 2. The cyl head is now off and the condition of the cyls, pistons, head and valves can be assessed. My next task is to remove the sump, remove the big end caps and push the pistons out...then assess the condition of the piston thrust faces and ring lands. Considering the epic overheating situation...the internals stood up very well! Here are some pix of the engine in a partially dismantled state in situ.    |
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Post by enigmas on Jan 14, 2018 9:51:57 GMT
PART 3. Here's some follow up information regarding the condition of the Cyls, Pistons, Rods & Big End bearings: Cyls. Fortunately there was no scoring. The cyls were glazed slightly with no blued sections/spots or any discernable lip. This engine has done 365,000 kms reliably until the overheating episode. The glazing IMHO would be normal for a car that has covered so many kilometres. I gave the cyls a deglaze using a hone with 240 grit stones. Pistons. The top compression ring was jambed tight on the thrust sides of the pistons in several spots (generally 2) on all but number 1 piston. The very top edge of the piston above the land had just nipped the cyl walls on cyls 2, 3, and 4. The reason the engine compression read so low was that it was blowing past the 'jambed' section of piston ring and the skirt. Once removed the rings still illustrated useful tension. I carefully removed the top rings on each piston and checked the ring lands which were amazingly still well within tolerance for side clearance. The 2nd ring is slightly thicker...these illustrated no damage at all as did the ring lands The 3rd composite ring (oil control/scrapper) was flush faced with the piston skirt...so wasn't doing anything other than filling the ring land space. My view is that it had been like this for ages and was stuck in place by virtue of the carbon carried in suspension by the engine oil. This engine only used oil during short trips, stop start driving. On long trips...2 this year to Coolum, Queensland from Victoria it used no oil at all! Piston skirts. No scuffing literally no damage at all. Big End Bearings. The bearing inserts all checked out fine with negligible wear...likewise the bigend journals are in amazingly good condition. The car has had regular oil and filter changes, generally 2 a year during it's life. I'm getting a new std ring set from Repco ($55). Interestingly the oil control ring on this engine can be 2 sizes...either 2.8mm or 3mm. Mine are the former. So always check before purchasing. The compression ring and 2nd ring are the same but of different widths for all 1.5 engines. Here are some photos of the lightly honed cyls, and the conrods/pistons prior to and ready for refitting.         |
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Post by enigmas on Jan 14, 2018 10:34:05 GMT
PART 4.
The cyl head is currently being surfaced by a mate (Basil) at Headworks Murrumbeena. The valves will need reseating with new stem seals as well.
Reading the torque sequences for the head bolts, conrods and mains for this engine (WSM) is kind of interesting and in some ways archaic, if not confusing and on par with the cyl head tightening sequences of my 1942 WLA air cooled motor cycle (military workshop manual) where it's all done by 'feel' literally in the field...and I do mean field!
On this engine the bolts are specified 'torque to yield' (i.e., simply put...a stretch bolt) The head bolts are being replaced with new as the engine had a severe over heat cycle (daughters will do that!) but I'll be reusing the conrod bolts as that end faired well.
The method for torquing bolts is 2, 3, 4 or 5 stage, depending upon the application. First, torque all bolts to a given torque setting (quite low and in Nm as it's a metric car) then loosen all the bolts, then torque them back to the first setting, then tighten each through 90°, then 90° again....Take a guess what the torque reading actually is? God knows?.
I've got an accurate Warren & Brown tension wrench and I used this tool in increments to actually find the torque loading! If you're working under the car it's not always possible to pull a bar or wrench soothly around to 90°! Besides if the bolts are precisely manufactured the correct torque loading will provide the same yield (stretch) bolt for bolt.
In relation to the conrod bolts...I'll simply use the WSM two stage method on one rod on the bench, held in a vice to torque the caps... and then use my tension wrench to assess the torque loading. This will provide the torque figure to tighten the other conrod caps.
This is the head bolt tightening sequence per WSM.
Step1: 49Nm (in sequence)
Step2: Loosen fully in reverse order
Step3: 20Nm (in sequence)
Step4: Turn 90 degrees additional (in sequence)
Step5: Turn 90 degrees additional (in sequence)
Truly...I don't like the method!
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Post by nz on Jan 14, 2018 21:41:43 GMT
I bought a Honda that'd done that. Even after I did rings etc, it had low compressions. Turns out the valves were being held open a little. ($200 car...thought I'd get away without head work, duh.) I guess you're going to do the head anyway. Paul.
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Post by enigmas on Jan 14, 2018 23:13:16 GMT
It's been a great little runabout Paul and it still is, apart from the overheating incident. It's also had a new clutch, pressure plate etc, done a couple of years ago. As for the cyl head, yes it's being refaced and the valves reseated including new valve stem seals by a mate (cyl head specialist)...There's no point in doing half a repair! The things we do for our daughters.  (Vince) |
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Post by enigmas on Jan 16, 2018 2:31:20 GMT
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Post by Warwick on Jan 16, 2018 4:43:04 GMT
... My mate Basil at work. ... I'm glad you added that bit of info, Vince. As I scrolled down through the photos I began to think; surely it's not that long since I last saw you! |
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Post by enigmas on Jan 21, 2018 22:42:28 GMT
Finished the assembly work on my daughter's little Lancer coupe yesterday and fired it up for the first time since the over heating episode. Here's a very brief video from my phone of the engine running. A bit tappety...but I'll let things bed in for a while before readjusting them. The exhaust is clean running, it holds its coolant and the only smoke to be seen was oil contamination burning off the engine surfaces for the first half hour.  |
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(Vince)
