Northstar headgaskets...

[Cadillac Jim]

addilac -- since I got a Jasper instead of doing a Timesert job myself, perhaps I could make up a doormat using my Jasper invoice.

BBF -- if 15W-40 works for you, sure. You also do the WOT whenever it seems appropriate, and perhaps one a week is a good idea for any Northstar. But I would be wary of any oil that says right on the can that it is "thicker" than regular oils of its viscosity rating, particularly one that also has viscosity ratings higher than 10W-30. One oil change in an emergency, OK, sure, but running overly thick oil for a long time that can form shellac on burning or on hot pistons with too little flow, without WOTs, seems to be a recipe for stuck rings.

BBF -- chrfab makes sand buggy and off-road vehicle engines. Nearly all these engines are pulled down at least once a year, and rarely do they go more than three or four years between pulldowns. I would use MLS gaskets in one of these engines without a thought.

Perhaps we should look at the current GM part for head gaskets to be used for replacements on older Northstars, and ask high-volume long-established remanufacturers like Jasper what they use. These people will have experience with engines that are run on the street for over 7 years, which is the only real test. I would wager that all of these have special treatment such as non-galvanic sealing rings around the water jacket holes. Also, there are anerobic sealers that can be used with head gaskets to help keep water jacket holes sealed.

[samert]

This has always been GM's pos. I think there's more to the head bolt issue than the coolant story. I'm anal about maintenance and my head bolts pulled in spite of my efforts.

Here's one from the other end of the spectrum. Had the wife's 96 Eldorado since 98 I think. I'm pretty anal about PM's (oil changes, tires, brakes, etc) but I was just plain unaware of the importance of the coolant service other than the 100K service interval. I did have it changed at 100K but was clueless about the radiator tablets. Never put them in and still haven't. Car now has 167K miles on it and HG's still seem to be OK. Had a coolant leak once but it was one of the heater hoses that I could get to. Only reason I'm getting educated now is that it's leaking oil (again) and I've been lurking here looking for solutions. The half case seal was redone at 57K under extended warranty but appears to be leaking again.

Oh, and I have the dreaded PO741 TCC lockup transmission code. I'm still trying to get someone to tell me if that's the only code I have, will replacing the TCC solenoid correct it. Had it for at least 2-3 years now and dealer wanted $2500 to fix it. Said the Torque converter needed to be replaced. Just yesterday went on a 200 mile day trip running 80 mph on the highway. Cleared the code once I got on the interstate and it never returned while cruise control was set but as soon as I get into city driving using my foot the code will set almost immediately. Why is that?

If the TCC solenoid will correct it then I'm going to drop the cradle next Spring to replace it and probably pull the engine and replace it with a N* Performance rebuild. Wife wants to keep the car and I think it’s just a matter of time on the HG’s.

Needless to say the coolant will be changed out ASAP but I'm still not sure about the radiator tablets. Seems there are believers on both sides of the table on these.

[Cadillac Jim]

No one can tell you for sure what will or will not fix your transmission without opening it up. If the TCC code doesn't happen on the highway but only in city, it's likley that the TCC is simply sticking occasionally. If you've never had your transmission serviced, its likely that there is a lot of oxidized transmission fluid in there. You can check the transmission fluid level, color and smell; I don't know of a service that can run tests on it but you might call Blackstone Labs and ask them if they can test it or know someone that could. I would try servicing the transmission and giving it a couple of months.

The tabs are basically old-fashioned radiator sealant that GM found many years ago to be the best thing out there to seal micrcracks ("porosity") in aluminum blocks. They started recommending it for the HT-4100 and continued until after 2000. I think that most antifreeze currently available is (1) OAT-based and is silicate-free and (2) has a sealant in it that works with aluminum blocks because nearly all engines made in the last 15 years are aluminum-block engines with water pumps that don't like silicates, so you probably don't need to use the tabs unless you go out of your way to get retro antifreeze.

Don't underestimate the need for distilled water. Tap water is conductive and conductive coolant is a no-no for any aluminum in your cooling system, which is why manufacturers have been recommending distilled water in radiators for over 30 years. I knew of a 1970's Chrysler 440 that etched out the top of the thermostat housing from inside and shot water straight up; the housing was aluminum.

The guy who told you that code P0741 means that you need a new torque converter might well be someone you should never speak with again. Even if you wore coveralls, have a wild cowlick in the front, chew on a wheat stalk, have inch-wide short fingers, and speak with a thick Polish accent, saying that to you demonstrates incompetence somewhere in the chain and quite possibly a propensity to bid CYA repairs up front -- at best. A lot of guys here say that the TCC solenoid is a DIY job and have the pictures to prove it. If you can drop the cradle and get the tranny cover off, and are good at jigsaw puzzles, you can do it.

[KHE]

This has always been GM's pos. I think there's more to the head bolt issue than the coolant story. I'm anal about maintenance and my head bolts pulled in spite of my efforts.

Here's one from the other end of the spectrum. Had the wife's 96 Eldorado since 98 I think. I'm pretty anal about PM's (oil changes, tires, brakes, etc) but I was just plain unaware of the importance of the coolant service other than the 100K service interval. I did have it changed at 100K but was clueless about the radiator tablets. Never put them in and still haven't. Car now has 167K miles on it and HG's still seem to be OK. Had a coolant leak once but it was one of the heater hoses that I could get to. Only reason I'm getting educated now is that it's leaking oil (again) and I've been lurking here looking for solutions. The half case seal was redone at 57K under extended warranty but appears to be leaking again.

Oh, and I have the dreaded PO741 TCC lockup transmission code. I'm still trying to get someone to tell me if that's the only code I have, will replacing the TCC solenoid correct it. Had it for at least 2-3 years now and dealer wanted $2500 to fix it. Said the Torque converter needed to be replaced. Just yesterday went on a 200 mile day trip running 80 mph on the highway. Cleared the code once I got on the interstate and it never returned while cruise control was set but as soon as I get into city driving using my foot the code will set almost immediately. Why is that?

If the TCC solenoid will correct it then I'm going to drop the cradle next Spring to replace it and probably pull the engine and replace it with a N* Performance rebuild. Wife wants to keep the car and I think it’s just a matter of time on the HG’s.

Needless to say the coolant will be changed out ASAP but I'm still not sure about the radiator tablets. Seems there are believers on both sides of the table on these.

The sealant tablets won't do a thing for a leaking head gasket. They were intended to seal minor porosity in the castings, etc. to prevent small, nuisence coolant leaks. The factory stopped using them in '98 or '99 possibly as a cost savings measure after reducing porosity in the castings or just because customers complained they made the coolant look dirty. That said, it won't hurt to use them - I use them in all my cars as do a lot of members on this board. In fact, my '05 Deville is due for a coolant change in February and I plan to use the sealer tabs.

There is a specific troubleshooting technique in the shop manual for the PC0741 code. The solution may just be a pinched/kinked trans. cooler line. More complex causes could be a bad TCC solenoid, the torque converter slip is exceeding specifications, or the turbine shaft seals are worn or cut.

If the case half was re-sealed previously, I wouldn't expect it to be leaking again. It may be the oil pan gasket that is leaking now - the leak line will be below the balancer. The engine still needs to be removed to re-seal the oil pan gasket.

[samert]

This has always been GM's pos. I think there's more to the head bolt issue than the coolant story. I'm anal about maintenance and my head bolts pulled in spite of my efforts.

Here's one from the other end of the spectrum. Had the wife's 96 Eldorado since 98 I think. I'm pretty anal about PM's (oil changes, tires, brakes, etc) but I was just plain unaware of the importance of the coolant service other than the 100K service interval. I did have it changed at 100K but was clueless about the radiator tablets. Never put them in and still haven't. Car now has 167K miles on it and HG's still seem to be OK. Had a coolant leak once but it was one of the heater hoses that I could get to. Only reason I'm getting educated now is that it's leaking oil (again) and I've been lurking here looking for solutions. The half case seal was redone at 57K under extended warranty but appears to be leaking again.

Oh, and I have the dreaded PO741 TCC lockup transmission code. I'm still trying to get someone to tell me if that's the only code I have, will replacing the TCC solenoid correct it. Had it for at least 2-3 years now and dealer wanted $2500 to fix it. Said the Torque converter needed to be replaced. Just yesterday went on a 200 mile day trip running 80 mph on the highway. Cleared the code once I got on the interstate and it never returned while cruise control was set but as soon as I get into city driving using my foot the code will set almost immediately. Why is that?

If the TCC solenoid will correct it then I'm going to drop the cradle next Spring to replace it and probably pull the engine and replace it with a N* Performance rebuild. Wife wants to keep the car and I think it’s just a matter of time on the HG’s.

Needless to say the coolant will be changed out ASAP but I'm still not sure about the radiator tablets. Seems there are believers on both sides of the table on these.

The sealant tablets won't do a thing for a leaking head gasket. They were intended to seal minor porosity in the castings, etc. to prevent small, nuisence coolant leaks. The factory stopped using them in '98 or '99 possibly as a cost savings measure after reducing porosity in the castings or just because customers complained they made the coolant look dirty. That said, it won't hurt to use them - I use them in all my cars as do a lot of members on this board. In fact, my '05 Deville is due for a coolant change in February and I plan to use the sealer tabs.

There is a specific troubleshooting technique in the shop manual for the PC0741 code. The solution may just be a pinched/kinked trans. cooler line. More complex causes could be a bad TCC solenoid, the torque converter slip is exceeding specifications, or the turbine shaft seals are worn or cut.

If the case half was re-sealed previously, I wouldn't expect it to be leaking again. It may be the oil pan gasket that is leaking now - the leak line will be below the balancer. The engine still needs to be removed to re-seal the oil pan gasket.

I picked up a FSM on Ebay and it should be here any day, so I'll look through it on the PO741 code. I still can't figure out why the code only sets when I'm not using the cruise control. Even at highway speeds with cruise off it will set but not with cruise on. Strange.....!

The oil leak is up above the oil pan line on the back side. Looks like it stops around where the lower case half meets the upper half. Tough to see up in there. It was re-sealed, but that was 110K miles ago.

I'll figure it out next Spring when I drop the cradle.

[KHE]

This has always been GM's pos. I think there's more to the head bolt issue than the coolant story. I'm anal about maintenance and my head bolts pulled in spite of my efforts.

Here's one from the other end of the spectrum. Had the wife's 96 Eldorado since 98 I think. I'm pretty anal about PM's (oil changes, tires, brakes, etc) but I was just plain unaware of the importance of the coolant service other than the 100K service interval. I did have it changed at 100K but was clueless about the radiator tablets. Never put them in and still haven't. Car now has 167K miles on it and HG's still seem to be OK. Had a coolant leak once but it was one of the heater hoses that I could get to. Only reason I'm getting educated now is that it's leaking oil (again) and I've been lurking here looking for solutions. The half case seal was redone at 57K under extended warranty but appears to be leaking again.

Oh, and I have the dreaded PO741 TCC lockup transmission code. I'm still trying to get someone to tell me if that's the only code I have, will replacing the TCC solenoid correct it. Had it for at least 2-3 years now and dealer wanted $2500 to fix it. Said the Torque converter needed to be replaced. Just yesterday went on a 200 mile day trip running 80 mph on the highway. Cleared the code once I got on the interstate and it never returned while cruise control was set but as soon as I get into city driving using my foot the code will set almost immediately. Why is that?

If the TCC solenoid will correct it then I'm going to drop the cradle next Spring to replace it and probably pull the engine and replace it with a N* Performance rebuild. Wife wants to keep the car and I think it’s just a matter of time on the HG’s.

Needless to say the coolant will be changed out ASAP but I'm still not sure about the radiator tablets. Seems there are believers on both sides of the table on these.

The sealant tablets won't do a thing for a leaking head gasket. They were intended to seal minor porosity in the castings, etc. to prevent small, nuisence coolant leaks. The factory stopped using them in '98 or '99 possibly as a cost savings measure after reducing porosity in the castings or just because customers complained they made the coolant look dirty. That said, it won't hurt to use them - I use them in all my cars as do a lot of members on this board. In fact, my '05 Deville is due for a coolant change in February and I plan to use the sealer tabs.

There is a specific troubleshooting technique in the shop manual for the PC0741 code. The solution may just be a pinched/kinked trans. cooler line. More complex causes could be a bad TCC solenoid, the torque converter slip is exceeding specifications, or the turbine shaft seals are worn or cut.

If the case half was re-sealed previously, I wouldn't expect it to be leaking again. It may be the oil pan gasket that is leaking now - the leak line will be below the balancer. The engine still needs to be removed to re-seal the oil pan gasket.

I picked up a FSM on Ebay and it should be here any day, so I'll look through it on the PO741 code. I still can't figure out why the code only sets when I'm not using the cruise control. Even at highway speeds with cruise off it will set but not with cruise on. Strange.....!

The oil leak is up above the oil pan line on the back side. Looks like it stops around where the lower case half meets the upper half. Tough to see up in there. It was re-sealed, but that was 110K miles ago.

I'll figure it out next Spring when I drop the cradle.

If the PCM detects high torque converter slip when the TCC is commanded ON then P0741 sets. You could have an issue with the solenoid or the torque converter itself.

[Cadillac Jim]

From what KHE says, it is possible that you do need a new torque converter. Someone with a Tech II service computer or the equivalent (not just a code reader) could tell by reading the data stored when the code was set, which would tell exactly why the code was set, when it was set, etc.

I still would start by having the transmission serviced, particularly if it has never been serviced. To me, not even the viscosity of the fluid is necessarily in spec if you have more than 100,000 miles on it.

[samert]

From what KHE says, it is possible that you do need a new torque converter. Someone with a Tech II service computer or the equivalent (not just a code reader) could tell by reading the data stored when the code was set, which would tell exactly why the code was set, when it was set, etc.

I still would start by having the transmission serviced, particularly if it has never been serviced. To me, not even the viscosity of the fluid is necessarily in spec if you have more than 100,000 miles on it.

I did service the transmission last year, filter, fluid change etc. Did not correct the problem.

However, now that you mention it when the code first set I took it to a local tranny shop and the tech hooked up his scan gage and we took it for a ride and he was showing me on the gage how the transmission was measuring slippage so maybe it is the TC more than the TCC solenoid.

Can a bad TCC solenoid cause the TC to slip?

I'll need to figure this out before next Spring when I drop the cradle for the planned TCC solenoid change and review of the oil leak situation. I probably should just have the thing rebuilt since I'm also leaning towards getting a rebuilt N* Performance engine anyway.

[Cadillac Jim]

If you had your tranny serviced last year and you still have the problem, then the problem is electrical, or you are going to have to go into the tranny to fix it.

A bad TC is not something that I have seen, or would expect of a 4T80E short of radical abuse such as revving the engine in neutral or park and throwing the tranny into gear, or towing and allowing the tranny to overhead badly.

The TCC solenoid controls the fluid line pressures that control the TC and put it into the turbo mode and the hydraulic clutch mode, or unlocked and locked modes, respectively. Of course, when you look at it that way, a bad TCC solenoid can and will make the TC slip, and that's what throws the code. But what I am saying that a bad TC on a 4T80E is not something that I have heard of. Others here that have a lot more transmission experience than I do may have something to say here.

No one is going to be able to promise you that you won't need a TC, etc. You yourself won't know all the things that you need until you are finished with the repair and are ready to reassemble the transmission. And, you won't be absolutely sure until you drive the car afterward. But the whole thing sounds to me like either a wiring harness/connector problem or a bad TCC solenoid.

With the miles you have on the tranny and the fact that you are going into it for the TCC solenoid, lots of people will tell you that you are well-advised to replace the two shifting solenoids too, and perhaps other things like the oil pickup screen, filter, and perhaps a pump or whatever.