Ralph77

No did not restart it to warm it up. Did it warm yesterday afternoon. Then just let it sit overnight to do it cold this morning.

97grand4.0

So I have a better stupid laugh than that, friday night getting my 98 xj road ready pulled the asd and fuel pump relay to crank it over to purge the oil pressure sending unit...anyway...started it just now and UH OH a code! p1282 fuel pump circuit or throttle position voltage low...Panic....THEN i remember I pulled the relays.

Bugout4x4

Superb extra effort Sir. Absolutely displays the difference between warm and cold, and how much difference there can be from cylinder to cylinder.

I for one greatly appreciate you doing that.

BlueRidgeMark

I'm grateful, too. I had not paid attention to this before, and now the data is posted so I know the difference.

Ralph77

There is one thing that confuses me on this. I have a '01 Jeep Service Manual. A real Mopar one. Picked it up for free a couple years back off Craigslist. Since I have a CA Emissions '00 I figured everything should be exactly the same. So they tell you how to do a compression test as I stated in the first post. No mention of doing of starting the motor to warm it up. No where in there could I find the specs for what the compression should be. You would think they would list it right where the instructions for doing the compression test are. They could be in there somewhere but I can't find them. Anyway the couple people that did post the specs said 120 to 150 with a difference of no more then 30 between any two cylinders. One guy that stated this in a Youtube video said he got those numbers out of his Chilton Manual. So I am reading higher on a couple cylinders when warm. Number 2 at 170 so 20 above the 150. So it makes me think that if the specs stated are correct it should be done cold. Now having a reading of 155 when cold on Number 6 is theoretically above spec. But my friend and I are speculating that could be from carbon build up. I did do that dribble the water in the throttle body steam cleaning thing a couple years ago. And I probably should take her on the highway more often and open her up.

Bugout4x4

What I noticed on mine when I was rebuilding the engine, is that the valve heads tend to wear the seats oval shaped. And in some cylinders it was more pronounced and worse than in others. The valvetrain on these apparently does not push on the valve stems exactly inline as they should creating out of line wear on the valve guides and seats. This oval wear on the seats has to have some effect on the compression too.

Ralph77

I think I am going to run a compression test every year. But do it cold. I take out my plugs yearly to regap anyway. '00's having the coil bar so it is not like I have to keep track of any wires. Maybe an extra 1/2 hour and that is if I let my starter sit for a bit between each cylinder. Figure since I decided to do it cold, as well as warm, I have sort of a base line to work off of.

BlueRidgeMark

I don't trust anything that comes out of a Chilton or Haynes manual.

Bugout4x4

Absolutely, once you have a baseline and get to know a particular engine you are good to go. But doing the research like you did is what makes a good mechanic Ralph. Extra leg work to see what truly makes the clock tic is how the oldtimers got so good back in the day. They weren't just parts changers... They were parts rebuilders... they knew how the inside of the part actually worked because they had taken the extra time to take that clock apart. Why replace a whole turbo control unit on a cummins ISX for $250 when after you take it apart and look inside it turns out all that fails is a 15 cent O-ring.

Ralph77

With me it is all about maintenance. I picked this '00 up about 5 years ago now. Thought the price was reasonable for a kinda running but not really driveable project. Since I am older, don't have a life (LOL), and live a 1/2 mile from work I hardly drive her. And it is my DD and only car I own. So everything I do is done on a time frame and not mileage. I have put about 15K on her in the last 5 years. Oil changes and a lube get done in April and October. In April in an even year tranny fluid (only cause there is a drain plug on the pan), transfer case fluid, and anti-freeze get swapped out. This year I drained my PS fluid out of the reservoir and for the cost of about 12 oz of fluid think I will start doing that yearly too. Pull my plugs in April every year to regap so I figure I will throw the compression test into the equation. Crawl around under the Jeep every April and put a ratchet or wrench on every nut and bolt I can get at. I Fluid Film in October for the winter and power wash off in April. Thinking once I am done under there I might just Fluid Film in April for the whole year. Power wash and reapply every year in April from then on. Stuff is great but is mess when trying to work under the Jeep with the stuff applied. I swapped out my diff fluid for a synthetic a couple years ago so I just check the level when I do my oil changes. Thinking at some point in time would like to suck new brake fluid through the system. Probably just be a one time deal. I am little behind cause I have not done my anti-freeze yet. Also thinking will do a block test every time I swap the anti-freeze. Hey I bought the tool might as well use it.

Bugout4x4

That's what it is all about Ralph... Preventative Maintenance. And philosophically the PM concept can be applied to everything in life and it always pays off in the long run, like even family or spousal relations. lol