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Low compression along all cylinders

 
Old 04-02-2018, 03:02 PM
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Default Low compression along all cylinders

Hello, I purchased my first s2000 about a week ago with 163k miles (from 2nd owner, older religious man) and had it inspected by a mechanic. Compression test came out pretty even @ 1- 183, 2- 180, 3- 190, 4- 175ish. The car sat for 3-4 hours at the mechanic before the compression test was done, not sure if engine was warmed up or not.

My questions are:
1) would doing a compression test on a cold engine have a big impact (and should I consider doing another one)
2) what can one do to increase compression numbers? rebuild? new engine? any other options?

Thanks
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Old 04-02-2018, 03:36 PM
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Cold compression will always be lower than warm compression, aluminum expands a fair bit as do the cylinder walls. The important part is that it's even, I'm sure if the car is driven for a few miles and checked again it'll be closer to spec.
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Old 04-02-2018, 04:18 PM
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Originally Posted by Slowcrash_101 View Post
Cold compression will always be lower than warm compression, aluminum expands a fair bit as do the cylinder walls. The important part is that it's even, I'm sure if the car is driven for a few miles and checked again it'll be closer to spec.
"important part is that it's even" where the hell did this myth originate from? low comp is low comp. Last motor we check with 180 comp had a 45% leak at the rings... Doesn't matter if its even across the board if all the number are low. Just means its REALLY worn out.
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Old 04-02-2018, 04:54 PM
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Originally Posted by Charper732 View Post
"important part is that it's even" where the hell did this myth originate from? low comp is low comp. Last motor we check with 180 comp had a 45% leak at the rings... Doesn't matter if its even across the board if all the number are low. Just means its REALLY worn out.
Or the gauge isn’t calibrated.
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Old 04-02-2018, 05:16 PM
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Originally Posted by Charper732 View Post
"important part is that it's even" where the hell did this myth originate from? low comp is low comp. Last motor we check with 180 comp had a 45% leak at the rings... Doesn't matter if its even across the board if all the number are low. Just means its REALLY worn out.
My motor has made 180-200 comp across the board, but leakdown numbers are 0-5% on all cylinders. You can't just look at some numbers on the internet and surmise that the motor is bad.

OP: Yes, cold numbers will be lower than hot numbers. Gauge matters. Furthermore, do a leakdown test.
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Old 04-02-2018, 05:37 PM
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Thanks, now I can sleep easier. Mechanic said he ran compression after a test drive, but it probably wasnt a long one. I'll be scheduling a compression and leakdown with somebody that specializes in s2000's. Anyone have a recommendation for San Diego? If not ill probably take it to LA.
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Old 04-03-2018, 02:09 PM
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if you're unsure, you could always follow up with a leakdown. or a wet compression test.
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Old 04-03-2018, 02:34 PM
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Originally Posted by jungle View Post
Anyone have a recommendation for San Diego? If not ill probably take it to LA.
Infinite Motion in San Marcos. They'll take care of you.
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Old 04-03-2018, 05:08 PM
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If you're mildly handy you can do a compression test yourself! Compression testers are pretty cheap.
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Old 04-03-2018, 07:26 PM
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.. But don't use the one from Harbor Freight, it consistently reads low. Mine read in the 185 range on brand new HF gauge. Recovered from panic and rented better gauge from Autozone. Got 235 range numbers. This board is full of reports of low readings with HF gauge.

Maybe the one mechanic used was from HF?

I don't think the HF gauge just reads low across the board. Maybe it just has trouble reading super high compression.

For most cars, compression nearing 200 is outstanding. I suspect many mechanics don't really know how to do a compression test, or are just lazy, and instead just make up numbers they assume will be believable and never actually do the test. They don't realize this engine is capable of numbers around 240. So the numbers they assume will make customer happy actually freak us out.

Or maybe they gauges are similar to HF, and have always seemed reliable, maybe they work fine and are reasonably calibrated when numbers are below, say 200. But just can't handle the pressure of our motors.
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