HT4100 4.1, 4.5, 4.9 Discussion, stripped cylinder head bolt hole on a 4.9L in Cadillac Engine Technical Discussion; I bought a '92 Sedan DeVille a few years back and loved the car. A few minor cooling problems, and ...
I bought a '92 Sedan DeVille a few years back and loved the car. A few minor cooling problems, and heater core problems, but all were dealt with by a chevy dealer. Then, my baby suffered a severe front end hit&run while parked. Upon driving home after the incident, I noticed a bad overheating problem. I babied the car home, and the next day (after checking the fluid levels) I drove it to the insurance office and then to the chevy dealer. The total distance was about 5 miles, and though it was running hot, the engine never got too hot and the fluid levels were still fine. The dealer (chevy) assessed the body damage (destroyed 5 mph bumper assembly and complete doghouse) and noted the overheating problem. Long story short, the body damage was fixed, but the dealer said they never could find any overheating problem. Over the next 800 miles they got the car back 7 or 8 times, but still could not find any overheating problem. (which never stopped them from charging me for a new radiator or a complete cooling system flush) Ultimately, the cooling system failed, (exhaust in the reserve cooling tank), and subsequent conversations with the dealer failed to get them to agree that the problem was as a result of their lack of proper proceedure. (they admitted to never checking the thermostat, the radiator cap, the cooling fans or noticing that the top of the radiator was very hot, while the bottom was cool) Not wanting to pay the dealer 17 hrs @ $85.00/hr to figure out (what I think they did that) was wrong,(rip the motor down to the block to see if heads/block were cracked or head gasket was blown) I drove the car home and tore the motor down myself. With the help of my $100.00 GM service manual, I did the job in about 4 1/2 hours. In the process I discovered the the right bank head gasket had blown. I decided to have the heads completly reworked, and a complete valve job w/all surfaces redecked and the intake glass beaded, for which I spent $185.00. (However the gasket set was $104.00.) Anyway, upon reinstalling the heads, I discovered that the #4 cylinder bolt hole was stripped. (all bolts torqued to 38 lbs and then to 68 lbs without any problems, but when I tried to torque #1, 3 and 4 bolts to 90 lbs., I discovered that the #4 bolt hole was stripped) The #4 bolt hole is right next to the #8 cylinder, which is where the head gasket had blown. I then set about trying to find a helicoil kit to repair the hole (not available at the dealer). In my quest, I ended up talking to a Cadillac dealer who informed me of the following: the '92 4.9L motor was the "daddy" to the northstar, the engine design wasn't real good (aluminum "box" around steel sleeve cylinders, and cylinder head bolt holes way down in the journal). And he also said it is NOT UNCOMMON for those holes to strip, including, upon impact. He also advised that any time they do heads, they timesert (helicoil) all 20 cylinder head bolt holes. He said they had run into too many problems not doing so. He also said he wasn't surprised that the chevy dealer didn't find the problem, because no chevy engine is like the 4.9L caddy engine, and they rarely if ever work internally on them.
So, after this long essay, the question I have is "Has anyone out there ever experienced stripped cylinder head bolt holes on a 4.9L as a result of a front end impact? Do you know of this problem at all?"
Again, Wes is correct. The thread repair is definately a MUST on any of the Aluminum Cadillac engines from the HT4100 up. A for the impact actually CAUSING the stripped bolt, it can be a contributing factor but it would rarely cause a perfectly good bolt/thread assembly to fail.