ENGINE OVERHEATED , OIL IN THE RESERVIOR
Sounds very much like a blown gasket. To help diagnose, pull the dipstick and see if you can tell if any anti freeze in oil. Pull oil filler cap, check it for residue. Finally, look in the crankcase (under the valve cover) to see if you notice a "milkshake" looking discoloration to engine oil. When a headgasket does "blow" it allows air to enter the coolant system causing pressurization. It also allows anti freeze to enter the affected cylinder, and oil to enter into the cooling system or coolant to enter the oil.. Another sure way to self diagnose HG is to run engine to operating temp, check exhaust for white smoke (steam) and a sweet smell (anti freeze) . Also a severly blown gasket would allow a noticeable loss of coolant. If none of these symptoms are present, you might look elsewhere such as faulty water pump, bad radiator cap. The absolute best way to check for a blown gasket is to do a cylinder leak down test. This is where a device which screws into where the park plug goes is attached and forced air is injected into each cylinder. The readings will indentfy exactly which cylinder is affected by the loss of gasket material to the cooling jacket and this of course, would be where pressurized air and coolant entering combustion area and oil delivery occurs. This isn't an expensive test either.
There are two schools of thought on HG repair: optimum replace it. Others have gotten good results with head gasket repair chemicals which plug the leak or break in the gasket. Do your own reasearch and of course, it is up to you if the cost of a head gasket repair, the possible damage already done (depends on exactly how hot engine got) vs. what the vehicle is actually worth. I've known prices to replace the HG to range from 600 and up. I've also known a repaired HG to blow again within a few thousand miles. If you do replace th HG, check around. Depending on how hot the engine got, you may have warped the head and it must be checked for warping or possibly, cracking in order for the new gasket to "hold" If either, it has to be machined which will add to the total cost. A mistake people often make is to fix a vehicle for sentimental reasons. I'd say if there are no other issues and the vehicle has given you good service up to now, it may be worth it. Bt a very high mileage, poorly maintained vehicle usually is NOT worth the cost of a major repair. Then again, some vehilces have a known history of HG failure: certain year model Caddilacs, Subarus, Range Rovers Toyotas etc- ALL have documented histories of a "design flaw" which causes HG failure, mostly steel bolts set into an aluminum block. Check your specifc year and make onlne. Find a reliable mechanic. I f after you do some self diagnosing, you think it IS the HG, do the leak down test first. Then make your best decision.
Feb 28, 2013 |
1998 GMC Sonoma