: Cylinder head torque?
05-22-10, 02:59 PM
Ok, guys, I could use a little advice, please. I just replaced head gaskets on my 2000 SLS with 101,000 miles. It had the classic overheating issue (no smoke, though) and had a new radiator, stat, and water pump. After dropping the cradle (easiest engine removal I've ever done) and removing the heads, I observed that both gaskets exhibited bunching and deterioration. There is no doubt in my mind that they were indeed defective. One bolt on each bank was kind enough to take the threads with them so I installed Time-Serts in all of the holes. The installation and reassembly went perfectly except for the cylinder head torque sequence. I'm not sure my angles were right. The car overheats even faster now than before I "repaired" it. Still no smoke, though. Cylinder head tester confirms exhaust gases in cooling system. So here's the question: do I just snug up the bolts a bit or do I risk loosening them and going through the whole sequence again. I'm concerned about the inserts loosening up if I loosen the bolts. I'd appreciate any guidance you guys could offer. Thanks.
If the inserts where installed correctly, they should not come loose. Might try retorquing.
05-23-10, 02:25 PM
Thanks, Ranger. I have seen several torque sequences. 30 ft-lb +70 degrees+60 degrees+60 degrees (190 total) is the one I used. Is that the best one? I'm using Fel-Pro gaskets. I ran the car for about 7-8 mins and the temp gauge only went slightly over half. In your opinion, do you think I'm ok?
I'm not sure of the torque sequence without checking the FSM, but someone who has done it will chime in.
"Slightly over half" is far from overheating. I certainly would not tear back into it based on that alone.
I got this is from AJ for using the stock stretch bolts:
Tighten the left cylinder head M11 cylinder head bolts to 30 N?m (22 lb ft ) in the sequence shown.
Tighten the left cylinder head M11 cylinder head bolts an additional 60 degrees in the sequence shown
Repeat the sequence turning each bolt another 60 degrees.
Repeat the sequence again turning each bolt a final 60 degrees (total 180 degrees).
Tighten the M6 bolts at the front of the cylinder head to 12 N?m (106 lb in).
05-24-10, 07:06 AM
Thanks. I'll give it another go. Although I didn't let the gauge go much over halfway, I knew something was wrong because coolant started blowing out of the reservoir and the upper rad hose was VERY HOT. After shutdown, cool off, and restart, cylinder head test confirmed exhaust gases in cooling system.
I know you thought you had a bad HG, but you might have a different problem. It seems like it takes more than one bad bolt on each bank to cause overheating. I think I had 2 bad ones on one bank and 3 on the other - must have been the 3 that was causing the problems. So, you might have a crack somewhere?
05-24-10, 09:27 PM
There was definitely at least one breach between #5 cyl and the water jacket. I did however have repeated interruptions while torquing the heads and I can't say that I didn't make any mistakes while doing so. I'm going to retorque tomorrow morning and post my results. Why is it that the prettiest things give us the most trouble?
05-25-10, 02:41 AM
If you have not run many heat cycles the bolts may not be locked in, so you can loosen and retorque them. I got interrupted torquing them and the "old guru" said it took a few heat cycles to lock them in so it was OK to redo them before it was run ( or really heated ).
There have been a few cracked blocks and damaged heads lately, There is a possibility that you had both a cracked block and bad head gaskets. Possibly a head surface was nicked.
The timeserts are the weakest of the thread repairs but I've had good luck with them. Careful installation is very important with them.
05-25-10, 02:03 PM
do you have some trick for getting both valve covers off while the motor is in the car? always wanted to double check my timing after doing my heads. i think its ok but taking off the covers is a pain. the I/E timing marks on both banks are aligned and never will vary. crank at TDC, both sets of marks are either at 12 oclock or 6 oclock.
05-27-10, 11:25 PM
Ok, I retorqued the heads, idled the car for an hour then ran it hard for 30 miles. Temp gauge never went past 12 oclock position. No exhaust in the cooling system, either. Whew! Gonna sleep well now. Thanks for the input, guys!
Glad to hear that.
05-28-10, 04:38 PM
so how did you get the valve covers off on a seville?
05-29-10, 04:02 AM
It was really pretty straightforward. There was plenty of clearance on the firewall side. It came right off. The front side was only a little more challenging. I had to remove the water pump drive pulley, of course, and the water pump tensioner. If you remove that big plastic radiator cover and the right side motor mount nut to lower the engine on that side, the valve cover bolts are easy to get at and you should have plenty of clearance to slide the valve cover out. I did remove the ignition modules and spark plug boots. That gives you more "wiggle room". I also think that spending a couple of minutes taking the hood off saves a lot of aggravation when working on the firewall side. I think it took me an hour and a half including the cylinder head retorque.