Toyota L Weak and Overheating Engine-Newly Overhauled

We have overhauled a Toyota L engine just this week and came to a puzzling issue on why it lost its power and is overheating.

Prior to overhauling the engine had overheated due to the radiator hose bursting.  It was immediately addressed during that day and everything was fixed and we used the car onto the occasion we went through.

However, after going back home the owner noticed that the coolant was being mixed with oil. The oil cooler gasket was replaced and to make sure everything was fine the cylinder head gasket was also replaced. Those steps did not solve the issue, the more the car emits thick white smoke.

This time the owner decided to let the engine overhauled.

The car was brought to the mechanic and the engine disassembled. Noticeably, the four cylinders were having the same uneven and marked sides.

The mechanic recommended that the cylinders be replaced with a standard size or oversize it with a 0.50 mm.

The owner happened to decide on the 0.50 sleeves be oversized. He brought the block to the Machine Shop for oversizing and went ahead and bought all the 0.50 piston, piston rings.

Weak and Overheating Engine-Newly Overhauled-0.50 size piston

After one day he went back to the Machine Shop because he was called to decide on what will they do. On the image below they have shown the owner that the sleeve has a crack around near the top and they don’t recommend it for oversizing rather it should be replaced with a standard.

Weak and Overheating Engine-Newly Overhauled-oversize cylinder

Since he bought all the oversize piston and piston rings through an order, it cannot be returned and the only remedy is to buy a standard sleeve then oversize it. It was an unexpected additional expense, however, the parts have to be utilized and no other choice.


The four standard sleeves were rebored and honed

After these sleeves were rebored and honed the engine is ready to be assembled. With new overhauling gasket, it includes the cylinder head gasket, the oil cooler gasket, new crankshaft oil seal, new camshaft oil seal, new cylinder head cover gasket, new crankcase cover gasket, and others. New sets of 0.50 sleeves, 0.50 piston, and piston rings.

The engine assembled with a new look, freshly cleaned inside and outside.

The engine attached to the body and the new engine life is first started successfully.  The sound is fine enough and you are contented with what you have done. The noise is just fine and it needs breaking-in for hours before it is normally used again for services anywhere.

Road Testing

After one day we tested it on the road and upon climbing up the hill there was no power even to the first gear.  It could just move on a plane lane and when you forced it to an elevated road it overheats and stalls.

The coolants are obviously circulating both oil and water that clearly puts the impression that the coolant pump is working fine.

This is the first time I experienced a newly overhauled engine with no power.  It’s a puzzle I and the mechanic have to discover.

I wish my readers could help in the solution of the issue at hand.  Please kindly post your comments down below the comment box.

What do you think is the reason behind why this engine has no power instead of a renewed strength and life? What steps and solutions should be done to restore this engine to its power?




6 thoughts on “Toyota L Weak and Overheating Engine-Newly Overhauled”

  1. Thanks for describing everything you did so far. I am not an expert, and you may have thought of this already, but as far as I know the four main reasons for an engine to lose power have to do with air, fuel, compression and spark. So maybe the air filter is clogged up and reducing the air flow. Less air will result in less power. The fuel injectors could get clogged or the Pistons could wear down.

    you sound like you know more about cars than me so you probably thought of that already. But you asked for suggestions so I’m just trying to help. Thanks!

    • Thanks, Chuck. I know even the unexpert people can tell something that can help even the experts. What you have mentioned as the causes of weak engine power are correct.  In this case, the engine is diesel so it has no sparkplug.

      Before the engine was assembled I made sure that the injection pump will do its function right so I let it overhauled by the specialists on injection pumps. The air filter is not an issue then.

      The solution just came that is it took a longer time in the breaking-in of the newly overhauled engine.

  2. I suggest you checked the thermostat and also the pump.  I think the cause could be leakage of the water from the thermostat, it should be checked. Also, It could be an issue with the coolant if it is totally dirty, it causes various problems. These are the things that have caused my car to overheat on occasions. I suggest you try them out

    • Thanks, RoDarrick for the suggestions.

      On the case of the engine oil contaminating the water, it’s the oil cooler that is leaking for there was a perforation on the steel itself.

      The overheating is not an engine problem, meaning not inside it but outside and it’s the radiator fan cooler that needs repair. Ultimately dried of silicon oil, so we have restored it.

      The weak power has been mysteriously solved by the longer time of breaking-in for the oil to be properly sealed by the piston rings.

  3. The story about the Toyota L weakness and overheating engine when in fact it was overhauled newly. However, there are things which are naturally compatible to a certain model and tinkering with parts just because it was a mistake may create more challenging issues, this particular story was they have used the oversized parts to the engine and it’s the piston and the piston ring itself that is the problem and the oversized parts. Of course, without proper fitting and with size deviation problems of losing traction and power on an elevated road would result and to add up it is a great danger. It is better to spend more than lose, your limbs in the process. mechanics though understand the intricacies of the right parts to the machine but not as good as the expert engineers on this. It’s a good case study though for all of us who are interested in machines.

    • In racing motorcycles and cars they would love to oversize the sleeves with new pistons and rings and they love doing it. The reason is that there is an added power with larger pistons that pumps the engine. 

      At first, the smoke is so thick bluish-white meaning, it is not properly sealed and oil is passing between the piston rings and sleeves. With this situation, it needs more time in the breaking-in so that the spaces between the pistons and sleeves be ultimately sealed.


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