I'm not sure what to make of this.

[CarlaValentine]

The freeze plug leak is likely fixable, depending on the size and cause of the leak, with a new freeze plug, a cement designed for the purpose, the sealant pellets, or some combination of these.

It appears to be leaking around the bottom half of the plug at the seam. It's very slight but it's there. I am going to do a coolant flush, put some fresh coolant in and some bar's leak and see if that helps. If not then I will look into a cement of some kind for a new plug. It's a very minor leak so it can hold off until I get the more pressing issues taken care of. Thank you though. I didn't think it was going to be fixable.

[Cadillac Jim]

Engine problems can cause decrease of catalytic converter efficiency. Excessive oil burning over a short period, such as you see with an overfill, won't hurt it because it will simply burn off the accumulated carbon the next time you take it out on the highway. But other things, like long-term leakage of coolant into the combustion stream, will eventually kill the cat, if not clog it.

But the most common problem that results in a clogged cat is the element cracking. As you know, the core of the cat is a monolithic ceramic element of generally cylindrical shape with a honeycomb pattern of holes running down it, and exhaust gases pass through these holes. Traces of platinum and other catalysts in these holes causes oxygen and NOx to burn the CO/HC, generating heat, water vapor, CO2, and nitrogen.

If the element cracks, the first thing that happens is that the holes don't line up exactly at the crack, thus you have mild to moderate clogging, as you apparently have now. You may see some white powder downstream from the cat. You may or may not hear a little rattling from the cat, during idle, startup, shutdown, or even rough roads. As the cracking progresses to disintegration, the rattling will get worse and you have clogging, and pieces of ceramic move down the system and clog your mufflers, too. Once the rattling dies down and you hear a milder crunchy sound from the cat, the mufflers are gone, too.

If you ask a muffler person why a cat element cracks, in my experience you will not get an answer. Every one I have asked says that it just happens, and I believe that the ones I have asked just don't know. In my opinion, you can get a cracked cat when

• You high-center the car over something that stresses the cat enough to crack the element, as in a high speed bump that you don't see, or a high-slope driveway that enters a street over a curbside.
• Someone damages the cat with a jack.
• I have seen people crack a cat by hitting it really hard with the heel of their hand while it was on a grease rack.
• Loose or missing exhaust system mounts and hangars, so that the exhaust system bangs around on potholes or other jolts to the car.
• Massive backfires. Think running with a bad FPR until this happens when you try to start it hot.

Another problem is that cats are really fragile and this is not often recognized by those who ship and handle them. In my experience 50% of new cats have cracked elements before the box is opened. I would hope that this isn't typical but that's what I have seen.

[KHE]

I've also recently discovered a pretty bad case-half oil leak. I'm not going to bother with trying to fix that though...not unless I have to tear the engine apart for some other reason as well. It's not leaving puddles...it's just annoying.

Most of the time, the case half just seeps - rarely will it drip to the ground. There is no pressurized oil path around the case half. The oil distribution plate that is between the oil pan and the lower crankcase half will leak to the ground with time and miles and there is pressurized oil in that area. Unfortunately changing the oil distribution plate requires removal of the transmission to get the exhaust crossover pipe out of the way in order to remove the oil pan.

[CarlaValentine]

I've also recently discovered a pretty bad case-half oil leak. I'm not going to bother with trying to fix that though...not unless I have to tear the engine apart for some other reason as well. It's not leaving puddles...it's just annoying.

Most of the time, the case half just seeps - rarely will it drip to the ground. There is no pressurized oil path around the case half. The oil distribution plate that is between the oil pan and the lower crankcase half will leak to the ground with time and miles and there is pressurized oil in that area. Unfortunately changing the oil distribution plate requires removal of the transmission to get the exhaust crossover pipe out of the way in order to remove the oil pan.

Here's a picture of where it's leaking from. I believe it's the case-half. It leaks along this side and the rear by the firewall. Note- this was taken after I had wiped some of the oil off to see where the leak was coming from. Regardless, it's not a major crisis I know.

[CarlaValentine]

Engine problems can cause decrease of catalytic converter efficiency. Excessive oil burning over a short period, such as you see with an overfill, won't hurt it because it will simply burn off the accumulated carbon the next time you take it out on the highway. But other things, like long-term leakage of coolant into the combustion stream, will eventually kill the cat, if not clog it.

But the most common problem that results in a clogged cat is the element cracking. As you know, the core of the cat is a monolithic ceramic element of generally cylindrical shape with a honeycomb pattern of holes running down it, and exhaust gases pass through these holes. Traces of platinum and other catalysts in these holes causes oxygen and NOx to burn the CO/HC, generating heat, water vapor, CO2, and nitrogen.

If the element cracks, the first thing that happens is that the holes don't line up exactly at the crack, thus you have mild to moderate clogging, as you apparently have now. You may see some white powder downstream from the cat. You may or may not hear a little rattling from the cat, during idle, startup, shutdown, or even rough roads. As the cracking progresses to disintegration, the rattling will get worse and you have clogging, and pieces of ceramic move down the system and clog your mufflers, too. Once the rattling dies down and you hear a milder crunchy sound from the cat, the mufflers are gone, too.

If you ask a muffler person why a cat element cracks, in my experience you will not get an answer. Every one I have asked says that it just happens, and I believe that the ones I have asked just don't know. In my opinion, you can get a cracked cat when

• You high-center the car over something that stresses the cat enough to crack the element, as in a high speed bump that you don't see, or a high-slope driveway that enters a street over a curbside.
• Someone damages the cat with a jack.
• I have seen people crack a cat by hitting it really hard with the heel of their hand while it was on a grease rack.
• Loose or missing exhaust system mounts and hangars, so that the exhaust system bangs around on potholes or other jolts to the car.
• Massive backfires. Think running with a bad FPR until this happens when you try to start it hot.

Another problem is that cats are really fragile and this is not often recognized by those who ship and handle them. In my experience 50% of new cats have cracked elements before the box is opened. I would hope that this isn't typical but that's what I have seen.

I did accidentally bottom the car out back in February over a large chunk of ice on the road, but I'm not sure what it hit. Could something that happened that long ago be causing problems now? I'll start it today and pay close attention to the cat to see if there is any rattling coming from it.

My new cat hasn't come in yet...I guess I will have to wait until tomorrow.

[KHE]

I've also recently discovered a pretty bad case-half oil leak. I'm not going to bother with trying to fix that though...not unless I have to tear the engine apart for some other reason as well. It's not leaving puddles...it's just annoying.

Most of the time, the case half just seeps - rarely will it drip to the ground. There is no pressurized oil path around the case half. The oil distribution plate that is between the oil pan and the lower crankcase half will leak to the ground with time and miles and there is pressurized oil in that area. Unfortunately changing the oil distribution plate requires removal of the transmission to get the exhaust crossover pipe out of the way in order to remove the oil pan.

Here's a picture of where it's leaking from. I believe it's the case-half. It leaks along this side and the rear by the firewall. Note- this was taken after I had wiped some of the oil off to see where the leak was coming from. Regardless, it's not a major crisis I know.

The case half seam is directly in-line with the balancer pulley bolt. The case halves come together at the crankshaft centerline. It looks like you have some oil seepage from the timing cover seal as well as leakage form the oil distribution plate which is between the oil pan and the lower crankcase half.

[CarlaValentine]

I've also recently discovered a pretty bad case-half oil leak. I'm not going to bother with trying to fix that though...not unless I have to tear the engine apart for some other reason as well. It's not leaving puddles...it's just annoying.

Most of the time, the case half just seeps - rarely will it drip to the ground. There is no pressurized oil path around the case half. The oil distribution plate that is between the oil pan and the lower crankcase half will leak to the ground with time and miles and there is pressurized oil in that area. Unfortunately changing the oil distribution plate requires removal of the transmission to get the exhaust crossover pipe out of the way in order to remove the oil pan.

Here's a picture of where it's leaking from. I believe it's the case-half. It leaks along this side and the rear by the firewall. Note- this was taken after I had wiped some of the oil off to see where the leak was coming from. Regardless, it's not a major crisis I know.

The case half seam is directly in-line with the balancer pulley bolt. The case halves come together at the crankshaft centerline. It looks like you have some oil seepage from the timing cover seal as well as leakage form the oil distribution plate which is between the oil pan and the lower crankcase half.

Oh. Lol. I guess I was wrong.

Thanks for the clarification. I didn't realize the case-half seam was that high up on the engine. I've had to add a quart since my last oil change, which isn't too bad considering I am due for another change in a couple weeks.

[CarlaValentine]

Today was a good day.

My brother installed the new cat without any trouble at all. The one that came off it was BAD! It wasn't broken at all, but it was so clogged up that you couldn't see through it at all. Shop air couldn't even be blown through it at 180 psi. It was completely black. After the new one was installed it was running better, but still not quite right. The idle was still fluctuating a bit, and it seemed to have a misfire and still a slight loss of power. The ISC motor was taken off, cleaned and adjusted again. That helped with the idle though it's still not perfect. I need a new ISC and will hopefully be able to get a new one next week some time.

It took a little time to figure out the misfire. It was blatantly obvious that there was one, but even after doing a power balance check over and over again I couldn't narrow it down to a specific cylinder. There also wasn't a misfire code set at all by the OBD system. After taking it for a test drive to see if that may help a little I could smell fuel very strongly. Running out of methods to check for the culprit of the miss, we started pulling spark plug boots while the car was running to check for spark on all cylinders. Bingo! Cylinder 8 had no spark at all. Being that I recently changed the plugs and wires, I figured coil was the best bet. My brother replaced the coil with a known good one that he had in his shop and the misfire went away. I believe this misfire is what likely caused my cat to go bad.

She's back to her old self again! Running flawlessly aside from the slight idle fluctuation, but that will be repaired soon. Now that all the major running issues have been taken care of I can start working on all the little things. I'm so happy right now!!!

[Texas Jim]

Carly,

I am glad you had a good day today and fixed most of your problems.

Sounds like you made some real good progress.

Congratulations to you.

[JimD]

....My brother replaced the coil with a known good one that he had in his shop and the misfire went away.

Would you be willing to mail the defective coil to me? ?

[CarlaValentine]

....My brother replaced the coil with a known good one that he had in his shop and the misfire went away.

Would you be willing to mail the defective coil to me? ?

I could do that...but can I ask why you would want me to?

[JimD]

.... but can I ask why you would want me to?

Reasonable question.

I have been collecting four-coil Northstar ignition system reports/data for several (many) years.

What "might" result from this exercise could be a reliable method of identifying a failed coil with a simple Ohmmeter test.

There is a thread somewhere on this board that relates.

[CarlaValentine]

.... but can I ask why you would want me to?

Reasonable question.

I have been collecting four-coil Northstar ignition system reports/data for several (many) years.

What "might" result from this exercise could be a reliable method of identifying a failed coil with a simple Ohmmeter test.

There is a thread somewhere on this board that relates.

That makes perfect sense. If you PM me your address, I can get it sent out to you Monday morning.