2006 GMC Envoy Denail. 185,000 miles
I’ve been fighting an oil leak for a while. Today while changing the oil I think I finally located it. It’s on the front of the block and a ton of oil on the pully right below the thermostat housing. I can’t find a diagram so I’m not sure what that pully is (I think it’s the AC) but that doesn’t make sense. It’s gotta be the crankshaft right next to it, right? Is there anywhere else that the front of the block could leak? Possibly related or other problems is low oil pressure. 40psi when running but drops down to 20 psi when hot and idling and I’ve already replaced the sensor. It also runs rough in idle*** and I have a check engine light that needs to be decoded.
So assuming it is the front crankcase seal or if not if I should replace it anyways while I try to find the leak, is it something I can do myself? I replaced the water pump myself and mechanicwise this doesn’t seem that much more difficult but do I need specialized tools or is it something I will get halfway through and get stuck on one key step? If I take it into a shop, how much would they charge me to replace it?
*** I’m going to change the fuel filter next and it could use a tune up.
Might be the timing chain housing.
Of course, knowing which engine you have would help.
Crankshaft seals are usually easy to replace, but you probably will want to replace the pulley at the same time, because they tend to get worn to the old seal.
Any chance it’s coming from the valve cover right above where you’re finding all the oil?
It’s common for those seals to parish.
Pretty sure it’s not. All the oil is above the water pum but I suppose it is worth a look again. I tried using the UV dye but that didn’t work so I’m going by where all the oil/dirt is on the block.
Is this the engine?
Can you annotate where you see the oil leak?
A little oil behind the crank pully (large on on the bottom) but there is a ton of oil thrown up on the pully just up and to the left (far left bottom in the picture). and some underneath the water pump. Above the water pump is clean.
My money is on the timing chain cover, and / or crankshaft seal.
If it is the crankshaft seal, my mechanic will charge under $200 to replace.
If it is the timing chain cover, am I right that they should also replace the oil pump if that is causing the low oil pressure and/or has 180K miles on it?
Oil pumps last forever. Low oil pressure is probably worn journals.
I would have someone experienced evaluate it, and not just shotgun it.
Ummm… would that mean replacing the crankshaft? Please say no.
At 185K miles, you are reaching the age where you will either:
a) Run it until it fails catastrophically due to low oil pressure, or
b) Have to invest a couple of grand to do a rebuild.
If you have lead a good, righteous life, the mechanic might find something trivial, like an oil pressure relief valve that is stuck open. But, I wouldn’t take that bet, sorry.
It’s weird because there is no knocking sound when I have “low pressure”. Some people have said it is probably the guage. Anyways I know I have a leak so I’ll get that taken care of first then see what happens. If they are replacing the valve cover gasket can they check to see if the pump is bad, needs a new filter, problem with the uptake, etc?
Are you a cartalk fan too ? 
Also, if I recall correctly, Tom and Ray used to recommend just keep adding the oil that you are losing, instead of trying to fix the leaks, for an old engine like this one. The theory was that once you open it up, there are other things that you will find are going bad.
Oh, yes. I’ve listened to them all, many times.
Any updates on the source of the oil leak?
I’m going to take it into the shop to get it diagnosed properly along with the oil pump checked, uptake checked, etc. so no update yet.
