2.7L Compression Test Numbers

I have a 1995 Tacoma 4x4 Single Cab 2.7L truck with 217k miles on it. I've had it for 11 years and bought it with 132k miles on it. It's been a great truck but it has me worried.

To be up front and honest, I've delayed doing some maintenance. Not because I'm dumb or lazy, just because I didn't know any better. It's only been within the last year that I've started working on my own truck and am self taught, so please take it easy on me. I've come a long way.

I've got an oil leak that appears to be coming from my valve cover. It started about a year ago and I've not really been that worried about it because it only loses about a half quart every 6 months or so. Over the last few days I've been getting things together to fix it and doing a little research. It wasn't until I was browsing the forums for topics related to valve cover gaskets that I realized that I should have been checking my valve clearance regularly. I just didn't know. As far as I know it's never been done. I know it's not been done since I've had the truck.

I got worried that I did major damage to my truck so I went out and got a Harbor Freight compression test kit to see if there was any major damage. The numbers have me worried. From front to back I got 125, 120, 120, 130. Knowing those numbers were low I added a little oil to each cylinder and retested to see if I could figure out why. With oil they measured 130, 120, 120, 140. Not significantly different in my book.

The truck runs about the same now as it did 11 years ago. It pulls plenty strong, idles slightly rough, and occasionally knocks when under load in low RPMs. Nothing has changed much, if any, since I've owned it.

With those low numbers should I be assuming that I've burnt my exhaust valves? Since the numbers are fairly consistent from cylinder to cylinder is it possible that maybe I just got a junk compression tester (It is HF after all) and it just measures low?

I've gotten pretty good at working on my truck but I'm not sure I'm good enough to tear the top off of the engine and start replacing valves.

 

I just read on a different thread that the 'right' way to do a compression test is with all of the plugs out. The person that posted that went on to say that if you leave the other plugs in then the engine is fighting to compress those cylinders and the overall reading will be significantly lower. Is there any truth to that? I tested mine one cylinder at a time with the plugs in the other cylinders. I guess I'll do another test tomorrow night for comparison.

 

Someone please correct me if I am wrong, I am not sure what the acceptable compression is for 2.7L engine but as long as your numbers are relatively the same in each cylinder you should be fine. If you are overly concerned you could probably do a leakdown test and find out more.

 

I had a shop, that I trust, adjust the valves and the owner claims that they did a compression test .... 200 psi. I don't know if he was exaggerating, but I would have been real happy with 180.

 

I'm looking forward to doing a second test with all of the plugs out although I'd be really surprised if the numbers jumped up by a large amount.

 

Id say 150 psi at a minimum.
Does it smoke or use oil?
Looks like,I could be wrong though.
https://www.google.com/url?sa=t&sou...dAcnHA8POaphzifIg&sig2=CDCWyMwYQkkU7yF8H8SYtw

 

No. It doesn't smoke or use oil other than the slow leak from the valve cover gasket. The plugs looked fine too.

 

OP, your numbers are getting low, but because they're all relatively close to each other, I wouldn't do anything yet. I've seen numbers as low as 90psi and the engine still runs. It's when the compression numbers are all over the map and differ widely is when your concern level should go up. As a rule of thumb, I've always used 10% difference between cylinders as a guide.

Also, because you're not burning oil or blowing smoke out the tail-pipe is a good sign that the engine is still on the healthy side. Others may feel differently, but I'd drive it till you had some other symptoms of fatigue (I.E. smoke/burning oil) unless you're looking for something to occupy your time and spend you $$ on. I hope this helps.

 

Thank you for your advice. I really appreciate it. I obviously need to replace the leaky gasket and it makes sense to adjust the valves while I'm in there. That surely won't hurt.

 

^^^^^^ agree 100%

sure it would be nice to see 150 compression on all cylinders like when they are new but none of our engines have that once they get that many miles. at 200+k miles I say 120 average is great and your engine is in good shape. these are not high compression engines with tight tolerances so you aren't going to see very high compression even on low mileage engines.

the valves covers don't get tightened down much so often you just need to give the bolts an extra 1/4 turn and it stops leaking, but be careful not to "just put them tight" because if you tighten them down all the way the gasket loses its ability to spring back and seal. to stop an existing leak you can try tightening them down all the way but if you do, then the seal will need replacing the next time you take the cover off.

you are making yourself worry about nothing, replace your valve cover gasket and lightly snug the bolts down all the way until they stop turning freely then give each one half turn more and its tight enough, if you see any leaks later give them another 1/4 turn more until you no longer see leaks

 

I might do a compression check on mine just to see where its at. My truck has fairly low miles. I think about 115k on the clock at the moment, doesn't burn or leak anything.9 I'm just curious to compare mine to yours as in that video I posted above he saw about 120 psi across the board on his, that might just be where these engines run..... I know my old 3rz had 317k on it ran like a top- didn't smoke or use any oil... It ran just as good the day Toyota bought it back off of me as it did when I first got it with the less than half of that mileage.

 

I really appreciate the support. When I get home tonight I'm going to test it again with all the plugs out just because I want to. I'll post the numbers.

 

elevation and atmosphere will have an effect on compression also. Higher elevation and warmer air will show lower compression as the air is less dense. As mentioned as long as there all fairly close between cylinders your fine. I comp tested my 300k 3rz last spring at 4500 feet elevation and got roughly 150 psi at each hole. That was with the injectors still plugged in, some like to do it dry with injectors unplugged so the gas injecting into the cylinder doesn't skew the numbers.

 

I just replaced my cylinder head on my 2.7L 3RZ because my #1 cylinder was at 30psi. My valves were smoked on that cylinder. The truck still ran but rough.

It didn't let me down on a 400 mile round trip with 50 miles offroad in the desert. Gotta love these little 4 bangers.

 

yep, the engine gets more cranking rpms with all plugs out so its the most accurate way to test compression.

 

Well, I have both good news and bad news to report.

I just redid my compression test with all of the plugs pulled. This time I got 150, 145, 140, 150. Obviously much better.

Working on a 20 year old truck is never easy. I managed to damage one of my plug cables so severely that I have to buy a new set. I moved on to replacing my transmission mount (I believe Toyota calls it a rear motor mount for some reason) and promptly broke off both of the bolts holding it to the cross member.

The woman that works the parts counter at my local dealership is incompetent so I expect that finding replacement bolts will be a nightmare. I may have found the source of a vibration that I've been chasing, however. There were only 2 bolts holding on the mount instead of 4. I'm sure there are 4 holes for a reason.

 

its best to get a set of ngk plug wires, I think this one is for your truck: http://www.ebay.com/itm/NGK-4447-Sp...Parts_Accessories&hash=item43d240a5a3&vxp=mtr

 

Thanks. Do you know if any of the auto parts chains sell them locally? Unfortunately this is my daily driver and I don't think my wife would appreciate having to drive me around for a week while I wait for them to be delivered.

 

they only took 3 days for me to get mine.

trouble is you buy them local your going to pay like $45-$50 for em

call around im sure the regular auto chains have them. from what I read you don't want other brands because they just aren't the same quality and don't last like the ngk will.

just use your part number NGK 4447

napa has em http://www.napaonline.com/Catalog/Result.aspx?Ntt%3dngk%2b4447%26Ntk%3dKeyword%26Nty%3d1%26Dn%3d0%26D%3dngk%2b4447%26Dk%3d1%26Dp%3d3%26N%3d0

and advanced auto http://shop.advanceautoparts.com/we...k+4447&vehicleIdSearch=-1&searchedFrom=header

and oriely http://www.oreillyauto.com/site/c/d...K_1278840_-1&mn=NGK&mc=NGK&pt=02815&ppt=C0334

 

Thanks.