Cyliner head removal 2004 4.6

[xlrlist01]

Hello Micky

Back at #16 above you said: "ill have to do a littke research andcask someone that knows more than me if you can actuall depend on that."

Did you ever get a reply or find out more?

Very many thanks

 

[mickeytee]

No i spoke with a couple of bolt companies and no one was willing to give me a figure. Sorry. I did keave meassGe with xeveral who have not got back

 

[xlrlist01]

Thanks Micky

Well, you tried. Sorry for the tardy reply, I've been busy.

I'm going to work on the basis of 10 degrees and 85 lb/ft (max both, which ever comes first).

 

[xlrlist01]

Thanks Micky. Yeah, makes sense. I'll await the reply. (I guess you mean head bolts not crankshaft bolts!)

An update. My Cadillac dealer left the coolant pressure test on for an extended period (probably over-night) (engine cold) and in the morning, using a high end (ie high definition and able to swing the head around and upwards while in the bore) boroscope, found a tiny weep in the #8 head gasket. Finally, found the fault with 100% certainty. I have asked they try to tighten the head bolts before they remove the heads, see what torque is required. This might indicate the head bolts were not stretched enough (or had lost stretch). I have also asked that they repeat the CO2 test in the coolant. The expectation is that no CO2 will be found. This would confirm that the weep is also acting as a one-way valve, ie coolant into the cylinder but no combustion gas out. From their experience, this can happen. I can also confirm the header tank was not showing any symptoms of over pressured or blowing off. I'll update with more information as it comes available. I can confirm they are separating the power-train from the chassis. Ie, a big job.

(For those who skip straight here, all the standard tests for a head gasket failure passed easily with no fault found, including pressure testing the cooling system, compression testing and a whole bunch of others. It was only by leaving the cooling system pressurized for hours that the weep has showed up, the official test is for a few minutes.)

With under 50,000 miles but having passed the 21st birthday, I'm considering what else to get replaced. Timing chain tensioners? valve stem seals? If anyone has other suggestions, get them in quick. TIA.

 

[mickeytee]

The radiator has 12-16 pounds of pressure while the cyinder pressure is 125-175 pounds. If a head gasket leaks there is no way on earth that the coolant pressure comes in the cylinder but combustion does not get into the coolant. Its been that way since the model tee . steve morris engine builder of 3000 hp racing motors just discussed this the other day. He builds heads for race cars with external cooling just for the fact if a cylinder blows a headgasket which is only used to seal compression as the heads are welded up with no cooling passeges next to the headgasket it may loose compresion but does not blow coolant all over the race track. Id have zero faith in a shop that claimed they had seen water flow one way. Thats why a gas test on the cooling will tell you if you have a cracked head letting water into the exhaust port or a headgasket issue. The new northstars don loosen bolts unless run extremely hot and then they are loose due to the block stretching. Usually requiring engine replacement due to warpage
As far as what to replace there are very few engine parts. Read about a owner in california who took hers in to get gaskets replaced and they talked her into chains and tensioners . tore it down and 6 months later she is told to remove it out of the shop because they cannot find parts. Nirthstars go for 175-250 miles without internal parts replacement



I can assure you water does not in any way form a one way seal as they seem to claim Good luck on the project. I would want a written guarantee before they touched my car that the problem would be ixed or cost me nothing. On a side note ive got an old dakota dodge shop truck with the magnum v/8 1994 . they are known to crack heads for no real reason and lose a little coolant into the exhaust. Ive put 150,000 miles on it since the problem started and just used up the first gallon of coolant i used to keep it topped off. Thats been 12 years and 12$ worth of coolant vs pulling it down,putting a new head on it that most likely would crack once installed. I sometimes follow the old saying if its not broke, dont fix it and if it is broke but your repair might not fix it then dont fix it.

 

[RubyRod]

An update. My Cadillac dealer left the coolant pressure test on for an extended period (probably over-night) (engine cold) and in the morning, using a high end (ie high definition and able to swing the head around and upwards while in the bore) boroscope, found a tiny weep in the #8 head gasket. Finally, found the fault with 100% certainty. I have asked they try to tighten the head bolts before they remove the heads, see what torque is required. This might indicate the head bolts were not stretched enough (or had lost stretch). I have also asked that they repeat the CO2 test in the coolant. The expectation is that no CO2 will be found. This would confirm that the weep is also acting as a one-way valve, ie coolant into the cylinder but no combustion gas out. From their experience, this can happen. I can also confirm the header tank was not showing any symptoms of over pressured or blowing off. I'll update with more information as it comes available. I can confirm they are separating the power-train from the chassis. Ie, a big job.

(For those who skip straight here, all the standard tests for a head gasket failure passed easily with no fault found, including pressure testing the cooling system, compression testing and a whole bunch of others. It was only by leaving the cooling system pressurized for hours that the weep has showed up, the official test is for a few minutes.)

With under 50,000 miles but having passed the 21st birthday, I'm considering what else to get replaced. Timing chain tensioners? valve stem seals? If anyone has other suggestions, get them in quick. TIA.

I'm not sure how attached you are to your car or to the LeakStar V8. I've made up my mind that if the LeakStar ever has to be removed from my car it won't go back in. I think it would make more sense to replace it with the LS2 or LS3. It will require a "tuner" to program things so that the electronics all still work but I think it would be preferable to spending a lot of time and money on the LeakStar. Just my 2 cents.

 

[mickeytee]

It requires a whole lot more than a tuner to install an ls. Its not a direct swap. All the electronics have to changed and a lot of fabrications. As far as leaking ive seen more northstars With clean oil pans than oily. The valve covers can and do leak, plus the cam phasers do leak. Other than that, its no more prone to any leakage than an ls. ive seen my sare of them soaked in oil. Im looking at a corvette that i may install a northstar in just to tick off the corvette guys. Ls engines if run hot will blow a gasket just like the northstar.

 

[xlrlist01]

Hi Mickey

I'm after another favor if I may:
1/ What is the head bolt tightening procedure for a later, 2007 say, naturally aspirated N*?
2/ Did the OEM head-bolts on my 2004 come with thread lock?

Background.
The Cadillac dealer has removed both heads from my X and used a torque wrench which recorded the peak torque for each bolt. The right-hand (1, 3, 5, 7) head bolts were all around 65lb/ft. The left-hand head-bolts though were not so good, around 55lb/ft at the front (#2) dropping to around 40lb/ft by #8. The head gasket was in excellent condition.

This looks like the Cadillac head-bolt fiasco from earlier, where the stretch to yield bolts have been over stretched at manufacture. They then work loose over time.

I note that the replacement head bolts and head gaskets are the same for all years of naturally aspirated (ie the 4.6) Northstar fitted to the XLR. The new head bolts come with thread lock pre-applied.

I'll write some more when I have more information from my dealer. The above explains the symptoms, almost certainly when hot there was enough clamping force to stop any leak, but when cold and the coolant system still pressurized, coolant could slowly seep into the #8 cylinder, causing the very brief mis-fire on cold start. The clamping force will increase as the engine warms up, because the aluminum head expands more then the steel head bolts.

I don't have the workshop manual with me right now, IIRC the 2004 head bolt tightening stages are:
1/ Some lowish torque setting (I see from above it is 22lb/ft)
2/ 60 degrees
3/ 60 degrees
4/ 60 degrees.

I'm curious to know if the 2006-2009 head bolt tightening sequence is different from the 2004-2005, as apparently Cadillac finally fixed this problem from 2006.

TIA

PS, oh yes, my dealer was very reluctant to tighten the head bolts as an experiment as they know they are close to pulling the threads out of the block. They tried one and it was around 85lb/ft. They were concerned that coolant could potentially be in the threads and this would cause false readings, stripped threads or other issues. I had already agreed that getting the heads off and searching for a cracked block or other woes was the right way forward. It was a judgement call and could just as easily go the other way for somebody else in the same position as me (ie, simply try tightening the head bolts using 85lb/ft as the maximum torque, though 75lb/ft might be safer. It is a risky procedure though, hence my dealer's reluctance).

 

[mickeytee]

Ill look but from what the bolt manufacture Arp is telling me some time ago, torgue to yield are a whole different animal than the old bolts you could actual check the torque on to see if any where loose. Its metallurgy and all i know about metal is Ozzy.

 

[xlrlist01]

Ill look but from what the bolt manufacture Arp is telling me some time ago, torgue to yield are a whole different animal than the old bolts you could actual check the torque on to see if any where loose. Its metallurgy and all i know about metal is Ozzy.

Thanks Micky

What do you torque head bolts to? Just asking.

 

[mickeytee]

On an aluminum head and block with arp lube 75 ft pounds in three passes 25 50 75

Your new bolts do not have thread lock. They would have sealant. Im not sure if any go into thevwater jacket which i doubt but tgey do havecacsealer. Thsts why each old hole has to have a thread chaser. From what im told the bolts dont get loose. If they are loose then they are stretched or they heads got so hot they expand enough to pull the bolts up causing the treads in the block which. is the weakest point to be stretched. With the old northstar you drilled tapped and put thread inserts in the block. ive tried to run a tap into them by hand and you cal teel the threads are deformed. The new northstar has longer bolts and if run hot to the point of stretching the block threads GM recommends block replacement.