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Thread: Mirage 3A92 Engine repair in process. (Problem: low compression)

  1. #31
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    Quote Originally Posted by Dave View Post
    the #3 cylinder was the worst but not by far. All cylinder had the same damage. Today I found a maybe .005-.010 thick white buildup in the water jacket on the cylinder, I don't know if it was build by an overheating event or if it caused overheating... It may even be an anti-leak treatment from mitsubishi like gm few years ago. Attachment 20954Attachment 20955Attachment 20956
    this look like a mineral build up same from the one you see at the bottom of a kettle..thats the reason why you cant put tap water on the radiator.



  2. #32
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    Dave,
    . . . . Did you complete the engine rebuild? I am concerned about the damage to the cylinder walls. Since the surface hardening is very thin any damage gets into the underlying aluminum which is very soft. I suspect that the block would either need to be replaced or iron sleeves be installed. Either procedure will be expensive. Also sleeves will increase the running temperature of the cylinder walls. My first engine when it failed did exactly what this engine did. At 64K miles I believe that my second engine is also going away!
    . . . . Was the machine shop able to get the scuff marks and scratches out of the cylinder walls? If not what did you do? I didn't like the look of the bearings. They looked over heated and oil starved. I will then build this engine up. The white powder on the coolant surfaces is a reaction of minerals in the water, additives in the coolant, and the aluminum in the engine. It is important to change the coolant every 30K miles or 3 years and to use distilled water. I always use Volvo coolant.
    . . . . When this engine gets where it is getting ready to go away I am going to buy a low mileage used engine. I will use this engine for the turbo setup. If I build a turbo engine I am going to have it sleeved. I will also have the pistons milled down so as to lower the compression to about 9 to 1.
    GOD Bless and Thanks,
    rich!
    2019 G4 Wine colored. 'Burgundy'
    130K miles, 37MPG average at 75-80 MPH with A/C and Lights
    I am on the second engine and trans! 4.5 months out of 18 in the shop!
    Not so happy any more!

  3. #33
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    Quote Originally Posted by Dave View Post
    Attachment 20957
    There was some assembly damage on the main bearing but nothing very bad on my opinion.
    Thanks for posting all the specs and info. Did the toyota bearings worl out? I’m thinking of making that change for better oiling while minds apart anyway

  4. #34
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    Whoa! These engines have ALUMINUM cylinders!? Like the Vega!? Like a Briggs lawn mower engine!?
    Karl

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    Crossbolt,
    . . . . Exactly! They do not have cast iron sleeves. Like I said I lost one at 72.5K miles and I believe that this engine at 66K is going away. It peaked at 210,210, 205. It is now down to 190, 185, 180. Still good numbers but going down. That isn't good!
    GOD Bless and Thanks,
    rich!
    2019 G4 Wine colored. 'Burgundy'
    130K miles, 37MPG average at 75-80 MPH with A/C and Lights
    I am on the second engine and trans! 4.5 months out of 18 in the shop!
    Not so happy any more!

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  7. #36
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    Quote Originally Posted by CROSSBOLT View Post
    Whoa! These engines have ALUMINUM cylinders!? Like the Vega!? Like a Briggs lawn mower engine!?
    For understanding, the construction of our engines has more than just a few similarities with the Daihatsu/Toyota 1KR engines, although that design is different. They don't have sleeves you can just remove, but rather much thinner sleeves with the block cast around them. They are not just sprayed onto the block as with some other makes. In south-east Asia, these 1KR engines usually do get rebored up to 0.5mm when required, although you are not supposed to re-bore according to the Toyota FSM. They run just fine afterward. I think our's is very similar. Later designs of that engine have oil jets for spraying into the cylinder and bottom of the pistons. Our's don't. FYI that sort of sleeve is explained in detail with pictures here:
    https://toyota-club.net/files/faq/19...engine_eng.htm

    Anyhow, the Mitsubishi 3A9x and very few other engines are cast using a pioneering high-pressure die-cast alloy method, which allows much more precise details to be created than with any other method. It is the base feature for making this sort of block possible which is cast around the sleeves.
    Last edited by foama; 11-04-2021 at 01:00 PM.

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  9. #37
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    Quote Originally Posted by foama View Post
    For understanding, the construction of our engines has more than just a few similarities with the Daihatsu/Toyota 1KR engines, although that design is different. They don't have sleeves you can just remove, but rather much thinner sleeves with the block cast around them. They are not just sprayed onto the block as with some other makes. In south-east Asia, these 1KR engines usually do get rebored up to 0.5mm when required, although you are not supposed to re-bore according to the Toyota FSM. They run just fine afterward. I think our's is very similar. Later designs of that engine have oil jets for spraying into the cylinder and bottom of the pistons. Our's don't. FYI that sort of sleeve is explained in detail with pictures here:
    https://toyota-club.net/files/faq/19...engine_eng.htm

    Anyhow, the Mitsubishi 3A9x and very few other engines are cast using a pioneering high-pressure die-cast alloy method, which allows much more precise details to be created than with any other method. It is the base feature for making this sort of block possible which is cast around the sleeves.
    Appreciate this description. However, the link coughed up "Error 404 Not found."

    Fummins last post was reassuring, to say the least! The kind of service his Mirage fleet sees would never have been repeated with the 60's Chevy Vegas.
    Karl

  10. #38
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  11. #39
    Quote Originally Posted by Mechanic View Post
    Like I said I lost one at 72.5K miles and I believe that this engine at 66K is going away. It peaked at 210,210, 205. It is now down to 190, 185, 180. Still good numbers but going down. That isn't good!
    GOD Bless and Thanks,
    rich!
    Quote Originally Posted by Mechanic
    WB changed my oil and filter and rotated my tires on Wednesday. I had them use Castroil Syntec 5-50. I have been using Syntec ever since it came out 40 years ago. I am happy with the way it performs and the wear factors of the engines that I have used it in. It isn't cheap but the peace of mind is well worth the cost.
    Quote Originally Posted by Mechanic
    If I didn't have the warranty I would go to 10K oil changes with the Castrol but they balk at that. So I do 7.5K changes. The oil is just starting to darken at 7.5K miles.
    Quote Originally Posted by mechanic
    I just got back from a long drive to TX by way of the FL Keys, Miami, and Cape Canaveral. I drove about 4.5K miles in 4 days. I now have over 20K miles on the Mirage. Ran great. I saw 58 MPG on one tank. My average overall for this drive was just about 40 and I had to run the A/C most of the drive. I was also running at 75 for most of the drive with some 80 MPH sections.
    I almost forgot that you prefer to use 5w50, change oil at 7500 miles, often drive at over 80mph for periods of time and pull trailers across the country with your car. I'm not saying that's why your engines keep piling up but figured it's worth mentioning.
    Mirage videos:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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  13. #40
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    I've thought for awhile that some of Mechanic's engine problems were due to running 5w-50. Is it possible that the engine is oil starved on the bottom end & cylinder walls during extended high rpm operation using 5w-50? Since at operating temp the oil has the viscosity of a 50w oil and the Mirage having only a 3.2 quart oil capacity is it possible that during high speed operation the oil return galleys may be designed for flow from lower viscosity oils (smaller diameter) which would cause the majority of oil to remain in the valve train starving the bottom end? I don't know, just conjecture on my part.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


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