Piston Slap: Head Gasket Headaches (Or Not)
TTAC Commentator spitfire writes:
Really enjoy the Piston Slap series. How can you tell the difference between a bad head gasket and warped block or head? I guess I’m not fully respecting the tight tolerances involved here because it would seem to me that once fluids start intermingling its way beyond a gasket to fix the problem. Thanks, keep up the good work.
Sajeev Answers:
Unless the car has well known fail points, like the Mark III Supra discussed in a previous Piston Slap (LINK: http://www.thetruthaboutcars.com/piston-slap-essex-archaeology-scorched-earth-supras/), there’s no way to know which part is at fault. Even if someone only “lightly” overheated a motor, it’s possible they are delusional and actually warped a cylinder head in the process.
Unless you own a late model I-6 BMW known to wiggle like a Daschund when it’s fragile cooling system bites the dust, or a Cadillac Northstar known to ooze fluids from every orifice, most signs of a blown head gasket happen in older vehicles. More to the point, a car that’s not especially valuable. If so, scrap the vehicle or do it right for the long haul: remove the head, take it to a machine shop, and replace the head gasket/bolts upon reassembly. Some cars have junky head bolts (Northstar, again) and others are torque-to-yield, so they must be replaced once you pull them out.
But wait, there’s less! If the head is warped and the car is obviously suffering from cooling system neglect, check the engine block for warpage too. Test every metal part, replace the gasket and replace the attaching hardware if needed. There’s simply too many labor hours involved to NOT do this repair right the first time.
Bonus! A Piston Slap Nugget of Wisdom:
If you aren’t the original owner, you’re in for more painful what-if scenarios. Perhaps the car overheated before, busted the head gasket, warped the head and the previous owner put Engine Block sealer (like Bar’s Stop Leak) in the system to band-aid the problem. Which we discussed before from the other perspective (LINK: http://www.thetruthaboutcars.com/piston-slap-morality-and-the-blown-head-gasket/). It happens!
Send your queries to mehta@ttac.com
More by Sajeev Mehta
Comments
Join the conversation
Had a friend who went through this on a second-gen Acura Legend (another known-problem-car Sajeev), and swayed me away from buying one. The thing with those is they usually pop the gasket at the #3 or #6 cylinder, and just burp exhaust into the cooling system. After a while (and some neglect) the motor overheats and it's a goner. The supposed best solution if the heads warp is to get new ones, since there's little to shave from them. Same for the block. And swap the hoses, heater core, radiator etc while you're at it. The only good thing about this, it led to the 3.5V6 swap from the first-gen Acura RL. Northstars, stud the block and do a full gasket job. Drive it another 100K.
A key to the high mileage club is to prevent overheating in the first place. Change all the hoses, t-stat, belts, etc on a schedule and you are usually not going to be changing a head gasket. Still, some engines will take out a gasket anyway. Pretty much all brands have (had) a weak engine in their portfolio. Should you be faced with such a problem, it is important to check the head and the block as already stated. I can't emphasize enough the importance of replacing the head bolts. Many are TTY and will not provide a proper clamping force after being in use. Also, I always used a proper thread lube like ARP when doing a head job. And watch the torque sequence.