Exhaust

[sgtshortt]

Hello All. I bought an 86 CJ7 2.5 L 4 speed. It had a small engine fire and I have rewired it and it runs, after doing a nutter bypass.

I replaced the valve cover, pcv, oil fill cap and the breather on valve cover.

It has an exhaust leak someplace, probably manifold or maybe needs a doughnut.

I am getting smoke coming out of the valve cover breather with a small amount of oil mixed in. I am also getting some smoke from the oil dipstick tube. It smells a little like exhaust.

The exhaust coming out of the tail pipe is very hot and not a lot of it.

Could my cat converter be plugged and causing this?

 

[Busted Knuckles]

Hello All. I bought an 86 CJ7 2.5 L 4 speed. It had a small engine fire and I have rewired it and it runs, after doing a nutter bypass.

I replaced the valve cover, pcv, oil fill cap and the breather on valve cover.

It has an exhaust leak someplace, probably manifold or maybe needs a doughnut.

I am getting smoke coming out of the valve cover breather with a small amount of oil mixed in. I am also getting some smoke from the oil dipstick tube. It smells a little like exhaust.

The exhaust coming out of the tail pipe is very hot and not a lot of it.

Could my cat converter be plugged and causing this?

Sounds like your describing significant blow by. Do you have a PCV valve plumbed and working ?

A very plugged cat, and your motor wont run, Im assuming you just got this running and have not driven it ?

If you have good flow out of your exhaust, then you dont have a plugged cat. You could have a partial plug up as well, these things are hard to diagnosis over the internet.

Im assuming that has an O2 sensor, pull it out if you want to know if its plugged, also an efficiently working non-plugged cat, will radiate several hundred degree heat. If its been idling for a while and its "cold" its plugged.

Might even be a little of both !. On that specific motor, excessive blow by would not be a "shocker" either, how many miles does it have on it ?

 

[sgtshortt]

I installed a new PCV on the new valver cover but it is not hooked up to anything.
This jeep has 127,000.

Do you think getting the pcv hooked to the canister will stop this?

If not how do I cure the blow by?

 

[Busted Knuckles]

The PVC is positive crankcase ventilation, its supposed to be taking the blow by gasses an putting them back into the motor via the intake. Ive not seen/touched a 2.5 in 20 years, so I dont remember where you are supposed to hook it up exactly on your intake or near your carb.

You need to hook that up, and then see how much "exhaust" is coming out of the valve cover / dipstick tube.

Blow by is the cylinder gasses that are making it past your piston rings, you fix it by rebuilding the engine, and in this case, that is one motor I would not rebuild, but thats just an opinion, my opinion. Id spend the money on a different motor.

You may find when you get the PCV hooked up most of your blow by is dealt with and its not a problem.

 

[sgtshortt]

PCV is hooked up and still smoking. I put in some seafoam and no joy. I just changed the oil and put in some ring repair stuff, about as thick as motor honey. Still smoking. I put my hand over the tail pipe and I am barely getting any exhaust.

 

[IOPort51]

did you do a compression check?? disconnect the pipe at the manifold and see if there is still a shortage of exhaust. That checks the cat.

PCV is hooked up and still smoking. I put in some seafoam and no joy. I just changed the oil and put in some ring repair stuff, about as thick as motor honey. Still smoking. I put my hand over the tail pipe and I am barely getting any exhaust.

 

[Busted Knuckles]

PCV is hooked up and still smoking. I put in some seafoam and no joy. I just changed the oil and put in some ring repair stuff, about as thick as motor honey. Still smoking. I put my hand over the tail pipe and I am barely getting any exhaust.

Before you go trying to remedy blow by, verify the cat is not plugged, you may be trying to fix things that are not broke. If you have little exhaust coming out and a leaking exhaust gasket, your starting to paint a picture.

Easiest way to check your cat is if its getting hot. Working Cats get hot when they are oxidizing un-burned hydrocarbons, should be several hundred degrees hot when the engine is hot. If its "cold" its plugged.

Try removing the O2 sensor unless you think dropping the pipe of the manifold is easier. This will release the back pressure and your excessive blow by may instantly stop. There also is a kit you can buy, it has a air chisel pointed "punch", you pop it through the pipe, you then thread a fitting in the hole and put a pressure gauge on it. Thats another way.

I would not spend anymore time fixing the motor, if you have little exhaust coming out of the pipe. Thats like changing out a toilet because the main sewer line is plugged at the foundation.

If all this eludes you, it could be taken to a competent shop. But for the love of time and your wallet, stop trying to remedy the blow by without knowing the condition of the cat.

 

[sgtshortt]

pulled the O2 sensor, no joy, still got the blow by, just my luck.
I'm going to fix the exhaust problem and drive it until I can get a
new motor for it.

 

[Busted Knuckles]

Okay, pulled the O2, did exhaust scream through the hole, or was it just a little exhaust and some noise ? Pulling the O2 is a diagnostic move, not really enough of a hole to exhaust the motor, but the amount of air coming out should give you some idea of whether or not the cat is plugged.

While I am no fan of that motor, hate to have you replace a motor for some other reason other than the motor, for even with a new motor, if you exhaust is plugged, the new motor wont run much better.

 

[sgtshortt]

Just a little exhaust and louder than normal. Still had the blow by too with the O2
pulled. I let it run for about 30 minutes to make sure it was warmed up.

 

[sgtshortt]

so I did the compression test.
#1 the plug was a little worn looking, it's been in about one hour of run time 130 psi and the smoke from oil blow by was about the same
#2 plug was almost black, same time in as #1, and psi was 60-70 and there was about the same amount of smoke.
#3 plug was black, SAA, psi was about 60 and a lot less smoke.
#4 plug looked good like it should, smoked the most when this cylinder was not hooked up, or at least looked like it, dark out, psi was 120.

So with this information my 24 year old 2.5 l motor is FUBAR.

I was thinking about swaping it for a AMC 258 i6 / 4.2l but I have questions.
#1 will it bolt on and work with the 4 speed already in the jeep?
#2 motor mounts work OK ?
#3 radiator OK?
#4 Starter?
#5 water pump and fan with pully OK?

 

[Busted Knuckles]

That sucks, Ive not swapped out AMC 4 cylinder, so I cant help you there, although the parts catalog for our jeeps in located in the "Docs" section of the site (bar near the top), that will tell you what you need to know, in the event know one pipes up with your answer.

Is money tight ? Allot of guys swap out there AMC 258 i6 / 4.2l 's for more power, they are pretty anemic, not much more power than your 2.5L. If money is tight, the AMC 258 i6 / 4.2l with a different carb and distributor will do fine, if not, and your pulling the motor, might consider an AMC 8 or another V8, or even a FI 4.0L from a newer jeep. Much more power and driveability too.

 

[sgtshortt]

ya a little tight. Just got back from an expensive vacation, property taxes , house insurance, two car insurances and no pay raise for the last four years.

I want to get the Jeep going to get my ball and chain off my butt about it just sitting there.

My plan is to get it going and save my bucks for a couple of years and put a AMC 304 or maybe a SB 350 and new Transmission into it along with a new rear because I'm sure a V* would not go well with the current rear.

I jusy found a AMC 258 i6 / 4.2l on ebay for $200. missing a few things but runs and does not smoke or have blowby.

 

[Busted Knuckles]

Might be money and time ahead to pull the 2.5, take a look at the head and cylinders, hone the cylinders and put rings in it, and put it back together. You can hand lap the valves if they are not burned. And check the main and rod bearings while its apart.

That would be the cheap route, if you really want the AMC 258 i6 / 4.2l , go for it, just will take more time tracking down odds and ends. Id pull the pan off the AMC 258 i6 / 4.2l and check bearings and throw an oil pump on it while your there.

 

[CJim7]

I've done the 2.5 to AMC 258 i6 / 4.2l swap. There's a lot more involved then one might think.
Motor mounts, radiator, drivelines, bell housing, tranny input shaft, reconfiguring the tranny tunnel, moving the crossmember...there's a lot of work involved and you want to have everything you need gathered up before you jump in.

 

[sgtshortt]

Well I know it's been a while since I did a post on this jeep. I pulled the motor and it was pretty obvious that it had some issues for a while as there was about ten gallons of oil sprayed all over everything.

I tore the motor apart. As I pulled the pistons I found that the middle two had rings that were broken into several pieces. The head looks pretty good and I'm going to hand lap the valves.

I took the block to a machine shop in town. He is going to dip the block in his solvent tank and scrub it down for me, hone the cylinders, swap the freeze plugs and swap the camshaft bearing for about $250. Not too awful bad.

Once I get it back about another $ 200 for new gaskets, rings and some engine paint and a steam cleaning under the hood.

As I go Ill take some pictures and post them.

 

[sgtshortt]

So here is a picture of what my 2.5 block looks like now. I picked it up from the machine shop Wednesday. I just painted it but no pics of that yet.

 

[CJ007]

Looks nice. I went on and off on mine for about 6 months as I added things to the list while I had it apart. Nice to see you made good progress!

 

[sgtshortt]

Got my motor painted, Allis Chalmers Orange. Why, everyone asks. Allis Chalmers tractors were manufactured here and both of my grandfathers worked there.

 

[sgtshortt]

I got my rings, gaskets and bearing in the mail a few days ago. The temp is going to be in the 50's tomorrow so when I get up from sleeping after midnights I think I'll got some work done on her.

I'll try and take some pics as I go.