: Catalytic Converter Question -



jcweller
08-28-06, 10:20 PM
:confused: I have a 2000DHS with about 123,000 miles. The SERVICE ENGINE SOON light has been on for about a month and I was told it was a Catalytic Converter code.

Last Thursday while trying to pass a car on a flat stretch the engine reved up towards redline, then overheated with several messages being displayed. The AC shut down automatically and the message panel said to shut down the car. I got it off the road and turned the engine off. I had the car towed (roll-on) to a local Northern Virginia repair shop.The tow truck driver said he smelled antifreeze/coolant in the exhaust.

Questions:
1. Would a restricted catalytic converter cause enough back pressure to blow the head gaskets?

2. Is the diagnosis of the wrecker driver the last word - is the most likely problem blown head gaskets? Is there another test the SHOULD be conducted?

3. What is the better path to follow here - I still owe more than the car is worth. Does it make sense to invest in a new engine, rebuilt engine, reconditioned engine, or a used engine from the recycler network?

4. I drive 70 miles one way to work every day, so I need reliable transportation.

Thanks,

JCW

Ranger
08-28-06, 10:41 PM
1. No

2. Is the diagnosis of the wrecker driver the last word? Absolutely NO. Is there another test the SHOULD be conducted? Absolutely YES. Have a cylinder pressure test done.

3. That is up to you, but a head gasket job, done properly with all 20 head bolt holes Timeserted should run $3000 - $4000 and will then be more reliable than a used engine (and much cheaper than a new one).

jcweller
08-28-06, 11:06 PM
So It was my turn for head gasket problems and not addressing the catalytic converter did not contribute?

Would it be better to have the cylinder pressure test done by the dealer?

Where can I find a list of repair shops in the Northen Virginia area who would even consider doing a head job on this car? Everyone I have talked to so far has said - "No way, too complicated, Put in a new engine"

I am assuming (dangerous word) that if I mention Timeserted to the dealer or a repair shop, they should know what that means.

Did Cadillac ever fix this problem? I was told the 98 DeVille I had was first generation and the 2000 DHS was the second generation and the head gasket situation was addressed and corrected. Was I the gullible receipient of anally applied combustion particles?

Ranger
08-28-06, 11:21 PM
Overheating does not necassarily mean head gaskets, though sweet coolant smelling exhaust is not a good sign.

Any shop or backyard mechanic can do a sylinder pressure test.

It's not complicated, but the drivetrain does have to be removed. Anyone who says that, is not familiar with the Northstar and you don't want them touching it anyway.

Yes, they should all know what Timeserts are. ++ TIME-SERT Threaded inserts threaded for stripped threads, threaded inserts, thread repair , stripped sparkplugs, sparkplug blowouts, threaded inserts threaded, repair stripped threads, stripped threads, inserts threaded inserts. (http://www.timesert.com)

GM made some inprovements to the Northstar in 2000 I believe. Longer head bolts and different thread pitch.

No, the CAT had no effect on the head gaskets. Did you keep up with the cooling system maintanence?

jcweller
08-28-06, 11:46 PM
Basically, when I check the oil at each fuel fill-up I look at the reservoir to see if there is pink fluid visible. Also, when I have the oil changed at 3000 to 4000 mile intervals I'm assuming (God I hate that word) that the shop inspects all the fluids.

Am I missing something here? It was down a little fluid a month or so ago and I stopped at the dealer to have them check it. They added some and sent me on my way. No one mentioned any "cooling system maintanence".

The drive train has to be removed? Ranger - There must be loads of misconceptions about the Northstar out there, if you are telling me that it's not that complicated to replace the head gaskets. I'm getting the feeling that the run of thre mill auto repair shop is not where this car belongs - how about like a speed shop - Redline Motors in Purcellville, VA?

Ranger
08-28-06, 11:54 PM
Not real complicated, but different. The toughest part is dropping the drivetrain, though I know a guy (tech) that was on another site and claimed he could have it out in 90 min. Ask if they are familiar with the Northstar. If not, leave. Find another shop or dealer that knows the engine and is competent enough to do the job. Many members here and at caddyinfo have done it themselves. Not rocket science, but Timeserting 20 bolt holes is time consuming.

jcweller
08-28-06, 11:58 PM
Is timeserting equivalent to helicoiling?

Could you expand on your cooling system maintenance comment - I thought, "If it ain't broke, don't fix it" - Curtis LeMay, SAC Commander

ewill3rd
08-29-06, 08:32 AM
JC,

Head gaskets blow for many reasons. The cooling system should be maintained, usually an overheat is the cause of head gasket failures. Some fail due to bolts pulling out of the block.
Your catalyst failure should have precious little to do with the head gasket failure, although it's possible that something happened the other way around.

You should never go for a "tow truck driver" diagnosis. Most of those guys are mechanics who couldn't make it or guys that only know enough to guess wrong. (not all)
Any diagnosis should be verified by a competent tech.

Timeserts are hardened inserts that you use instead of helicoils. Helicoil repairs have a tendency to pull out or come apart in certain applications. You can do a google search to find more info on time-serts but they are a pretty reliable repair if done right. The N* engine has an aluminum block that just can't take the punishment that it can dish out on itself.

If you do anything with the car, I'd advise having a reputable shop install time serts. Used engines are a gamble, new engines aren't available from GM anymore, you have to buy a short block and assemble it.

The cooling system should be maintained on a regular basis.
After driving for a long time the coolant basically loses it's ability to protect the components and can actually damage components if left unattended long enough.

jcweller
08-29-06, 07:14 PM
EWill3rd,

I've made some more calls today and had several more shops drop off the list. A local racing shop is willing to do the testing to diagnose what we have to work with. They believe that if you do the heads, and don't do the rest of the engine that you could force the bottom end into failure.

As I stated, the car has about 123,000 miles on it. I'm looking for some input from those who know - Does it make sense to just do the heads, if that turns out to be the fail point? I imagine I'm going to have the car for at least another two years because it will take that long to pay it off. At that point I'm facing retirement and no longer needing to commute 150 miles roundtrip a day! Would I be better off dropping a short block or a long block which Jasper claims to have available in and moving on?

I'm listening if anyone wants to offer an opinion.

JCW:rant2:

dkozloski
08-29-06, 07:23 PM
Replace the head gaskets only. The rest of the engine is bulletproof.

Ranger
08-29-06, 07:42 PM
I see you have been a member since '03. I am sure you remember our old Guru. He always said that the bottom end was, as Koz said, bullet proof, and never needed to be touched. He always said, just do the gaskets and Timesert all 20 bolt holes regardless of whether the threads where stripped or not and the resulting engine would last forever. Personally, I would not touch the bottom end.

ewill3rd
08-29-06, 09:21 PM
That is an old myth.
No harm in replacing the head gaskets with time-serts.
We do it in our shop every day, you'd cringe at the photos I could take of our heavy duty shop.
Engines in pieces everywhere.
It's almost scary. Our guys do good work though.

zonie77
08-30-06, 08:45 PM
The shop that wants to rebuild the bottom end is still using old technology. N*'s are good for 250-300K with reasonable maintainence. I've seen several apart with over 100K and the cyl walls still have the cross hatch and NO ridge. That wasn't true in the 60's-80's.

However the engine runs now (except for overheating) it will run after the head gaskets are replaced. Doing the bottom end would be a waste of money.

I don't like to disagree with Ranger but it is a complicated repair. It is not a technologically advanced repair. ( I think that's what Ranger actually meant)

It's complicated in the amount of work to be done. It comes out to be 30-40 hours work. Any good mechanic should be able to handle it. If the shops are all this busy I should go back to work!

How about ewill's shop? How far is it from you?

Ranger
08-30-06, 09:17 PM
I guess what I meant is that it is not rocket science, though probably not too much different than any other dual overhead cam engine. I will admit though, that I am not speaking from expirience, so if I am wrong, I stand corrected.

jcweller
08-30-06, 11:05 PM
eWill3rd - Are you in the Northern Virginia area anywhere?

Can any of you guiys recommend any shops around here?

I have been talking with the dealer in Winchester, however, they want me to sign a waiver in case the time-serts "don't take".

I think I'm going to call LIndsay in Alexandria - I have heard good things about that dealership - any reaction anyone?

I like the way you guys are thinking:
a. Verify the situation
b. Do only what is necessary on the topend and leave the bottom alone

I'll use that 30 to 40 hours number and see what other shops are quoting.

I appreciate you speaking up and helping me find my way.

I'll update the thread as I make a decision - again Thanks for the help!

JCW

zonie77
08-30-06, 11:46 PM
I guess what I meant is that it is not rocket science, though probably not too much different than any other dual overhead cam engine. I will admit though, that I am not speaking from expirience, so if I am wrong, I stand corrected.


That's what I thought you meant. It's a long tedious job (complicated in that respect) but not rocket science is how I'd describe it too.

Ranger
08-31-06, 12:33 AM
eWill3rd - Are you in the Northern Virginia area anywhere?

Can any of you guiys recommend any shops around here?

I have been talking with the dealer in Winchester, however, they want me to sign a waiver in case the time-serts "don't take".

I think I'm going to call LIndsay in Alexandria - I have heard good things about that dealership - any reaction anyone?

I like the way you guys are thinking:
a. Verify the situation
b. Do only what is necessary on the topend and leave the bottom alone

I'll use that 30 to 40 hours number and see what other shops are quoting.

I appreciate you speaking up and helping me find my way.

I'll update the thread as I make a decision - again Thanks for the help!

JCW
I think he is in your area.

ewill3rd
08-31-06, 07:25 AM
I am, in fact in northern Virginia, and I do in fact work at Lindsay Cadillac.
Call and talk to one of the service writers and they can give you a fairly accurate quote over the phone.
Try talking to Donna, she is at extention 8634 I think.
Our prices might be on the high side, but our heavy duty guys do these regularly and it's very rare that problems crop up.

I don't do heavy duty work so I probably won't be working on it, but one of our guys will do a nice job for you.