454 oil leak

gmc
2500

#1

Just purchased a 1994 GMC Suburban with 454 under the hood. Parked it in the driveway and drip drip drip. The leak appears to be coming from the front of the engine, possibly front driver side. Any ideas what it might be before I crawl under there…are there any common leaks on this engine?


#2

external oil cooler? Look at oil filter adapter.


#3

I’ll have a look, Thank you. I did read the oil filter thingy issue. Thanks


#4

At this vehicle’s age my first suspects would be crank and cam seals. It would not be unusual.


#5

Crap. How hard is the to change? 160k miles


#6

On a 454 in a vehicle the size of a house? You have your work cut out for you.
You gotta remove a whole lot of peripheral stuff to access the front of the motor. Best bet is to look for a how-to video on the internet and see if you feel up to it. Or review the procedure in a repair manual. Or both.

BUT, before doing that, try a UV sensitive dye kit. It’ll show you clearly exactly where the oil is running down from. You don’t want to start changing the seals before you know for certain that they’re the source.


#7

What color is the “oil”? Check the level of the power steering fluid, that stuff can drip a lot because it’s under high pressure, and in a vehicle this old it’s very likely the hoses and seals are bad.


#8

It right by the power steering, but the oil is black…then again it blows
around under there then lays in the protective pans until you park pointed
uphill…


#9

Mountain bike…yeah…no. I wouldn’t do that until u was sure. Thanks guys


#10

With all the blowing around and the delayed dripping, you’re right that the color is not a great indicator. Still, check the levels of all the oily fluids and see if one is low, and goes down quicker than it should.


#11

GM power steering fluid has a particular odor different from that of engine oil. Sniff both, if there is a difference, that is most likely power steering fluid. If they are the same, it could still be either.

But, Big block Chevy’s tend to leak from the REAR main seal rather than the front one. If you can get to the harmonic balancer, pull it, the seal is easy to replace but be sure to check the balance for a groove where the seal rides. It is common for the seal to wear a groove. There are thin sleeves that can be installed over the balancer snout so it doesn’t need to be replaced.

Pressure wash the oil oil and grime off so you can find the obvious leak. And it makes the repair easier IMHO because I hate dirty engine compartments.


#12

Copy
Thank you


#13

I think i found the leak. I sure hope so because it would be an easy fix. I think its the Oil Sending unit. If i pull the unit will oil drain out?


#14

Probably less oil will drip out vs removing the oil filter. Is sensor above oil level in pan? Most liquid does not flow uphill. Remove sensor. Install new sensor. It’s not like pulling your finger out of the dike.


#15

Great. I just changed the oil and added Engine Restore (does it really work) Rather not remove the filter


#16

Before you check everything, see if the oil pan bolts are really loose. If the pan has ever been off, that can happen. The 454 camshaft has no seal as it is driven by a chain inside the cover. The crankshaft seal can leak and it is a ten hour job in your back yard if you slowly do it. It is not a challenging job.

I don’t remember if the oil pressure sensor is in the back, like a 350 or in the front. Those can leak a lot.


#17

It was the oil sending unit.

I do thank you for the info


#18

How sweet it is! What could be a better, easier, cheaper oil leak to fix, eh? :smile:
CSA


#19

I am happy that somebody else mentioned the sensor before me. I killed a 350 and then changed the sensor along with the engine. 1976 Impala engine cost me $650. If they were that cheap and easy to change these days, I wouldn’t bother with synthetic oil. I would pay for a new engine in 70,000 miles on the money I’d save.


#20

Sending units can dump a lot of oil in a hurry. The other thing that would be on my list is a leaky pan gasket in addition to the other stuff mentioned. I lost a quart of oil a week with the pan gasket. $15 and a couple hours fixed it, but sending units are easy.