I have a 98 Jeep Cherokee that was in need of a new valve cover gasket. So I thought, sure, I can do that on my own. Everything was going fine. When it came time to put the cover back on I made the mistake of tightening the first valve cover bolt to the feet per pound spec instead of the inch per pound spec. Needless to say I over-tightened. So much so that I broke the bolt clear off. Oops.
So I brought the Jeep to my local mechanic to extract the bolt and rethread the hole. He calls me up and says he went too far with the drill and actually punctured into the radiator causing antifreeze to bubble up through the freshly drilled hole. Oops. Now he is replacing the entire cylinder head.
I question from all of this is what should I be concerned with? Obviously the equal compression within the cylinders, but is there anything else? For example, the exchange of different fluids in parts of the engine where they shouldn’t be? I want to avoid if at all possible returning to the mechanic and saying, “ever since you…”
“Most cylinder heads don’t have coolant flowing through them.”
BWAHAHAHAHAHAHAAHAHAHAHA!!!
Damn, mcparadise, I needed that. The only cylinder heads without coolant passages are air-cooled engines. Every liquid-cooled engine I’ve ever encountered have coolant passages. The heads get just as hot as the engine blocks and need coolant to keep them from melting. I can easily see drilling into a coolant passage through a valve cover bolt hole.
I’ve also seen engine designs where a head bolt or timing cover bolt goes into the cooling jacket. The factory solution in these cases is to use a thread sealer on the bolt to seal the hole once the bolt is installed. This cylinder head can be salvaged this way. Just remember the bolt location and reason you used thread sealer if this valve cover ever has to come back off.
BTW, you don’t really need a torque wrench to tighten valve cover bolts. (except maybe on a Lamborghini) They are not under any stress. Just use common sense for how tight they should be, then check and retighten them if necessary after a week or so. If you set the torque wrench for 50 foot pounds for example, alarm bells should have been going off in your head as you tightened the bolts and the wrench didn’t click.
Have to second Busted’s advice. There’s no need to even remove the head (if it hasn’t been done yet). It can all be done right on the motor, and the only charge would be a stud, some thread sealant, some shop supplies, and the mechanic’s time, oh, and tax.
A replacement head is overkill for this fix, and several hundred more than you need to spend…but it would most certainly fix the problem. Installation isn’t that tough, and you needn’t worry as much as you are.
I would have just tapped the now drilled hole all the way into the water jacket and installed a small pipe plug permanently instead of swapping a cylinder head. The valve cover and VC bolts can then be installed and removed normally if that need ever arises.
There’s no need to replace an oil pan because of a stripped drain plug or a cylinder head because of stripped spark plug threads and there’s certainly no good reason why a pricy cylinder head should be changed over something like this.
Just wonderin’, but who’s footing the bill on that head, gasket set, and incidentals?
Replacing the head is unnecessary to fix this, but if he’s accepting responsibility and paying for the new head than I give him a great deal of credit for “making it right again”.
If he’s charging you for the head replacement, I’m seeing red flags everywhere.
I have nothing to offer technically than has already been stated. Except perhaps that you need not worry about your radiator. What he tapped into was a coolant passage, not the radiator. He probably said “radiator fluid is bubbling up” and you may have misunderstood that to mean the radiator was drilled into.
The other thing I’d like to add is that this is not a serious problem. If this is properly repaired, you should not have lingering aftereffects.
As to the original problem, be aware that while valve cover gaskets can and do lose their compression over the years and seep oil, you should als replace your PCV valve. The problem is often compounded by the crankcase building pressure due to blowby and pushing oil past the gasket. The crankcase and the space under the valvecover are connected via the oil returns, and pressure in the crankcase is also pressure under the valvecover gasket.
Texases has a good point there. Sometimes (especially if there’s been any prior overheaing episodes) what can happen is that a cylinder head or intake/exhaust manifold may warp some just from the sheer act of removing the bolts. It curls so to speak.
I remember tearing a Chevy 350 down that had been seriously overheated and replaced it with a reman short block per customer request.
Neither exhaust manifold would even come close to fitting back onto the cylinder heads they were removed from. Both manifolds curled a bit and the holes on each end were a full 1/4" closer together than they were before the bolts were removed orginally.
