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I ran the test with the engine hot and all spark plugs out. Adding oil to cylinder 2 did not increase compression by much at all. I'm puzzled by the high reading on cylinder 3. Any ideas? I posted this on Toyota Nation as well, trying to get a variety of opinions.
Could just be a tighter cylinder. The 150psi I’d be a touch more concerned on but even then it’s not terrible. If oil didn’t change the numbers then that points to the head. Valve lash maybe.
What’s the status on this engine- newly rebuilt or how many miles? I don't know how you can get such high readings when the factory spec is only about 170 psi. Diffent piston in cyl #3? I’d try a different compression gauge.
put compressed air in #2 and you can hear if it’s going by the intake or exhaust valve or rings. 150 isn’t bad if they were all similar.
Last edited by Melrose 4r; Jan 4, 2024 at 04:28 PM.
The engine has 225k miles on it and I'm not sure if it's ever been rebuilt. I bought the truck in October. I already adjusted the valve lash according to the FSM and will test the compression again on Saturday. If cyls 2 and 3 are still out of wack I will try compressed air in cylinder 2 and see if I can hear where it's leaking. I am wondering whether my head gasket between 2 and 3 might be blown. Thanks for your insights.
The engine has 225k miles on it and I'm not sure if it's ever been rebuilt. I bought the truck in October. I already adjusted the valve lash according to the FSM and will test the compression again on Saturday. If cyls 2 and 3 are still out of wack I will try compressed air in cylinder 2 and see if I can hear where it's leaking. I am wondering whether my head gasket between 2 and 3 might be blown. Thanks for your insights.
I had that headgasket thought also, but you said you tested with the sparkplugs out so that would rule that out.And if it’s otherwise running fine…
curious to see what you find.
Further, that truck has tow bar mounts on the front. Maybe towed behind an rv? Maybe not as high as 225k miles?
Last edited by Melrose 4r; Jan 5, 2024 at 03:27 AM.
I'd do a leakdown test now. That'll give you more useful data, and help you narrow your focus on a more specific cause.
Most chain parts stores have the tool in their loaner program. You'll need a compressor, but a small one will suffice for this test. You're just building pressure. If you've never done one here's a Youtube video that's pretty informative.
I just finished another compression test and all 4 cylinders are at 180 psi. Since the last test I adjusted the valve lash and drove about 50 miles. I'm happy with the result, though I may still try the leakdown test out of curiosity.
I'd do a leakdown test now. That'll give you more useful data, and help you narrow your focus on a more specific cause.
Most chain parts stores have the tool in their loaner program. You'll need a compressor, but a small one will suffice for this test. You're just building pressure. If you've never done one here's a Youtube video that's pretty informative.
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Jan 4, 2024 | 09:50 AM
