Compression Test Results: Mantain or Replace Engine?

[Antznyopantz]

Performed a compression test to assess the health of my 98's 3.4.

Here are the numbers in the same configuration they occur on the engine. The bottom numbers are nearest the radiator and cylinder numbers are in parentheses.

183 (5) (6) 200
200 (3) (4) 150
205 (1) (2) 205

I believe spec is 178+ with no more than 14 psi difference between cylinders. Obviously number 4 is struggling. Number 5 isn't far behind it.

It has 404,xxx miles on it - is my daily driver - and runs ok.

I am about to take a road trip to Lake Tahoe and considering doing the maintenance on this one (water pump, tune up, radiator, etc) - or renting a car for the road trip and replacing the engine when I return (I've got one with 180k on hand - just no time to do a switch before leaving).

Informed opinions please. Think this thing has another 120k in to justify redoing the water pump? See if I can't make half a million? Or replace when I can?

Thanks!

 

[19963.4lsr5]

That 150 could be a valve adjustment but with your milage probably not.

Look at it this way, 150 is better than 120. Which is when I call it quits on an engine.


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[gamefreakgc]

My last engine registered 60 PSI on cylinder 6 and ran like a champ. Low compression is just loss of power, it'll run just fine and be safe. After 400k miles, those numbers are actually quite amazing. Drive confidently.

You can check the valve clearances easy enough during your timing belt job to see if you can help it out a little.

 

[plcfcng]

As long as you can pass smog you are ok it depends on how the rest of the Runner is weather to put more money into it. If you do a wet compression test with a couple of squirts from a oil squirt can motor oil or ATF works just fine and see how much the compression goes up. If that low one only comes up a little then you have a leaky valve that would require a head gasket job with a valve grind at a machine shop or a lapping of the valves I vote for the machine shop about 350.00 they will also adjust valve lash. If the compression do move up alot them the rings are worn. If it's valves an:bouncether 300.00 for a head gasket set and head bolts check rockauto for pricing If you do the water pump you are 1/3 of the way.

 

[Howardjes]

Compression Test Results Mantain or Replace Engine

I know there isnt a specific number of compression test figures, but one of my friends did full general repair including bottom end honing, changing pistons rings etc and he dialled 220 also here some of guys posted around 220. The thing is I want to do a remap my 743 cams on March, so I want to keep my engine in mint state before it.

 

[itowils]

Sorry to bump and old thread, but I saw this post and I'm running into the same issue with low compression in one cylinder and nearly identical numbers. I performed a wet compression test and my compression in cylinder 4 jumped from 150 to 220 (this was on a cold motor, so not totally accurate). The big issue with mine is that I'm throwing a misfire code on that cylinder, and it's constantly shuddering when up to temp. Pretty sure I have a head gasket leak into that cylinder too because I'm losing coolant and finding some moisture in that cylinder. Not sure what I should do at this point. I want to assume the motor is salvageable, but I also am thinking that I should just swap the motor for another one. Any advice would be great, thanks!

 

[spartacus]

Sorry to bump and old thread, but I saw this post and I'm running into the same issue with low compression in one cylinder and nearly identical numbers. I performed a wet compression test and my compression in cylinder 4 jumped from 150 to 220 (this was on a cold motor, so not totally accurate). The big issue with mine is that I'm throwing a misfire code on that cylinder, and it's constantly shuddering when up to temp. Pretty sure I have a head gasket leak into that cylinder too because I'm losing coolant and finding some moisture in that cylinder. Not sure what I should do at this point. I want to assume the motor is salvageable, but I also am thinking that I should just swap the motor for another one. Any advice would be great, thanks!

How many miles on the motor. 150 is not bad. 220 wet test could indicate worn rings but the numbers on 2 and 6 if either of them are low that could indicate a failed gasket. You are correct at the minimum it could be a head gasket but if it's a crack in the head then it gets a little more costly. Shop rates. DIY Head gasket job in my opinion are tidious but not that bad and worth it.

 

[itowils]

How many miles on the motor. 150 is not bad. 220 wet test could indicate worn rings but the numbers on 2 and 6 if either of them are low that could indicate a failed gasket. You are correct at the minimum it could be a head gasket but if it's a crack in the head then it gets a little more costly. Shop rates. DIY Head gasket job in my opinion are tidious but not that bad and worth it.

The motor is at 213K mi. right now, so not too insane, but not unreasonable for something like that to go out. I got the car at 197K, and changed the timing belt, water pump, cam and crank seals at 203K mi. My results for compression were 210 (CYL 1), 190 (CYL 3), 195 (CYL 5), 210 (CYL 2), 150 (CYL 4) & 220 (CYL 4 wet), 210 (CYL 6). The spark plug in cylinder 4 was totally shot, but I changed them all prior to the compression test, and the misfire was still there.

I was finally able to do a leak down test and right when I pressurized the cylinder, air was coming out of the radiator right away. Definitely have a blown head gasket

Now I'm just not sure if it's best to find and swap the motor, or just do head gaskets, resurfacing, etc. I'm leaning more towards a motor swap for the sake of cost and just being able to do a full reseal on it. Thoughts? Thank you!

 

[brillo_76]

I really don't think the v6 is known for bad or worn rings. These blocks are cast and can mostly take some heat. However the heads are alinuminum and can't take the heat. So if these engines goto H the heads mostly have a high chance of warpping. Thus blowing the head gasket.

It's quite possible you are just dealing with pure head issues.

The bummer is you won't know until you pull the heads and I get that you know what is what.

The prices of engines have really gone up compared to a few years ago. So it's a toss up as which is the best way to go. I am not sure what remfg heads for these days.. hoping a few more members chime in
.

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[gamefreakgc]

I agree, you'll struggle to find a used motor for under the mileage that you have. If you go the JDM route, they are pushing $2000. You can have the gasket repaired yourself or with a mechanic friend for a fraction of that price. You'd need a spare vehicle though as it's not a one day job. You'll want to have the head checked for cracks and resurfaced.