Engine lost compression?

Good afternoon,

The first thing I would do is a compression test to verify if you have an internal engine issue.

https://www.2carpros.com/articles/how-to-test-engine-compression

and

https://www.2carpros.com/articles/the-reasons-for-low-compression

Start there.

Roy

Okay, then the head has to come off to find the failure.

That will be a lot. With 230,000 it will be difficult to say if it is worth fixing. I would figure at least $1,000.00 to start.

Roy

You are welcome.

Always glad to help.

Roy

Did you do both wet and dry test? Also confirm it with a leakdown test.

That refers to how hard each piston is squeezing the air it sucks in. Even 120 pounds is low. The rest are real low. That can be expected with such high mileage. Piston rings seal the air in and prevent it from leaking out into the lower part of the engine where the oil is. Those rings normally wear with age. There's also valves that let the air in and the exhaust out. Over time they too will not seal as well as when they were new.

A compression test is just a fast way of determining the quality of each cylinder and its ability to make power equal to all the other cylinders. Your mechanic can also do a more involved "cylinder leakage" test, or "cylinder leak down" test. That will identify exactly what is responsible for the low compression. They will likely elect to not do that test with the mileage you listed because everything is going to be worn. No professional will do a valve job, for example, and leave all the other worn parts in the engine. This is likely a case where the engine served you well but it's time for a total rebuild.

It has 350,000 miles. It doesn't owe you anything.

You haven't described any problem or symptom so it's impossible to know what the best remedy is. You also have to look at how the compression test was done and if correct procedure was followed. The same conditions must be present for each cylinder's test. Looking at the numbers you listed, with each one getting lower in order, you'd have to suspect the procedure might be at fault. First of all, a battery charger should be attached to the battery and set to a slow charge rate. The compression test requires cranking the engine at least five revolutions and doing so runs the battery down. By the time you get to the last cylinder, it's going to be cranking slower which will make the readings lower.

During cranking, oil gets scraped off the cylinder walls. That oil helps the piston rings seal and do their job. It gets sprayed onto the cylinder walls when the engine is running at normal speed. When cranking the engine, it's running too slowly to spray oil so by the time you get to the last cylinder, it's going to read lower than normal. Experienced mechanics will check for that by repeating the test on the first cylinder after all four have been done. If it reads a lot lower than the first time it was tested, the procedure is more to blame than the engine wear.

The engine must also be warmed up before starting the compression test. If the mechanic gets interrupted in the middle of the test and the engine has time to cool down, parts contract and don't fit properly. The piston rings won't seal as well as normal.

I am a little confused with some of the info that you provided only because some of it is not related to the compression of the engine. Let's start with this guide that explains what and why you need compression:

https://www.2carpros.com/articles/what-is-engine-compression

Then we need to move onto finding out why you have no compression. So when you say you have no compression, what was the actual PSI reading on the gauge? Was it 0 PSI on each cylinder? If so, I would think we have a hole in the block or the head is not sealing.

Can you get a recording of what the engine sounds like when you are cranking it over? Thanks

You need to verify the valve timing