Friday, December 18, 2009

How hard is it to replace the rear crankshaft oil seal on a 1993 GMC Sonoma pickup?

My 1993 GMC Sonoma pickup has suddenly developed a massive oil leak. It is coming from the back of the engine. I believe it is the rear oil seal. I cant really tell there is so much oil all on the under carriage of the truck. It has just started and can use about a quart and a half in 50 miles of driving. It also has three codes showing. 13, 34, and 44. What would cause this? It has suddenly started drinking gas like crazy.How hard is it to replace the rear crankshaft oil seal on a 1993 GMC Sonoma pickup?
The trouble to replace the seal is you have to pull the transmission and the flywheel. A bad seal would not make your truck start using gas though. Something else must have failed to cause the oil leak and the gas usage. I wonder if your cam thrust face could have pushed out the rear cam plug allowing oil to spray out the back into the bellhousing and to alter the ignition timing to the extent you are getting bad gas mileage. Is the truck still running properly? It seems like you would notice a big change in the performance if the ignition timing was to suddenly get a good bit off.How hard is it to replace the rear crankshaft oil seal on a 1993 GMC Sonoma pickup?
13 Is O2 open


34 Is a MAP high vacuum condition


44 Is O2 lean





None of those have to do with oil. All could explain poor mileage. Unhook the battery wait a minute or two then run it again and see what codes come back. If you still get the 13 I would look at the wire connecting the 02 sensor. If it looks good I would replace the sensor and see what happens.





The rear main is a 1 piece design so like in the other post the engine and transmission have to be separated to get to the seal. Seals usually dont tend to all the sudden spring a major leak like that. I would be looking at things like the engine oil cooler lines. Im pretty sure that had them and those things will leak pretty bad when they get old. Look by the oil filter, you should see 2 tubes coming off it going up into the radiator. They usually leak around the filter which is at the back of the engine.





Other thing that could be going on is for some reason the crank case is under pressure, that would sure blow oil out of all sorts of places. Maybe even account for that MAP high code.
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