Oil leak at spark plug

[east302]

Truck is a 98 K1500 with the 350 and 220k miles. It’s my son’s first truck and we don’t know the history of it, but I doubt that it’s been rebuilt.

The head at the #5 plug is wet with the plug being wet on the threads. It doesn’t look to be coming from above (valve cover gasket). I do think that it needs an intake gasket replacement (it’s leaking at the front) and plan on doing that in the next few weeks.

The plugs are Delco 41-993 and look like hell. The electrodes are dry but the threads on 1 and 5 have a bit of oil gunk at the base. None smell like gasoline.

The only DTCs are for a wheel speed sensor and airbag. No misfire counts, seems to run fine. Meaning, if it wasn’t for the obvious shine on the head I wouldn’t think anything was up.

Plugs were all in tight, none obviously loose. I haven’t done a compression test.

What could be the cause of this?

#5 plug...

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[Erik the Awful]

Start with a full tune-up: spark plugs, wires, quality cap and rotor, fuel filter, air filter, and oil change. Then drive it a couple weeks and reassess.

Does it smoke? Does it lose coolant? Does it piddle on the driveway?

 

[stutaeng]

You just bought the truck? If the spark plugs were new, I would guess the PO greased the crap out them before he/she put them in....but looking at those spark plugs that's not the case, unless he reused them and didn't even clean the up?

Just looking at them, the oil looks external and not internal...

 

[east302]

Thanks guys. We bought it a few months ago but it hasn’t had the easiest life.

It doesn’t smoke or seem to go through a lot of oil but does have a small coolant leak that looks to be coming from the front of the intake. Kind of hard to tell with the accessory brackets in place. The only oil leaks look to be from the front seal area and/or the oil cooler lines.

I’ve cleaned it up, will put new plugs in and watch it. I’m hoping that it’s external somehow, just didn’t see a source above it. It looked to be wet just up to the exhaust manifold - I assumed it was a gasket leak there (exhaust fumes so bad it burns your eyes) which is why I pulled the manifold. I’ll replace that gasket as well.

 

[GoToGuy]

The plugs show that oil has gone away in the combustion process. Being localized around the plug a good guess is any oil drips from dipstick checks falling and being blown back by ram air from radiator. Swirling around engine compartment finding calm areas and landing place. Any of the oil cooler ( has an oil cooler?) radiator fittings flex lines, compression fittings leaking? Power steering lines? Pressure line age cracks compression fittings, leaks. Any leaks back of intake manifold dist base. Oil pressure transmitter is back there. I would do all the basic service things and wash down all those leaks to find if its staic age or a seal ,gasket, something thats failing. Does it have original poppet valve injection or upgraded injector kit?

 

[DerekTheGreat]

Engine is an oil burner, just look at all that brown fluffy stuff on 'em. Check the oil at every fill-up to get an idea of it's consumption. Have heard that when oil gets past the rings at high RPM, compression can force the mist up onto the plugs' threads.

 

[Erik the Awful]

It doesn’t smoke or seem to go through a lot of oil but does have a small coolant leak that looks to be coming from the front of the intake.

For the coolant leak:
1) Check the heater hose quick-connect fitting on the passenger side of the intake manifold. The Dorman replacement is good.
2) Check the plastic tee in the heater hose - I can't remember where it is, I just remember that mine failed on my '99 Suburban.
3) While you're at it, check the heater valve.
4) Carefully inspect the seam between the upper and lower intake manifold.

You're really hoping it's not #4.

Drive it, but start saving now because the more I think about it, the more I think it's going to need a rebuild (I should just stop thinking and then you'd be fine!). With the coolant leaks fixed, the longer you can drive it before it bites the dust.

If you do a bare-bones refresh yourself and nothing's broken, you can do it for about $200, but for some reason I always keep throwing more parts into the basket until I spend about two grand. If you don't fix the coolant leaks, plan on buying a new set of heads. Vortecs do not tolerate overheating. Junkyard Vortec heads are 50/50 on being cracked. Also, if you pull the intake manifold apart, it's worth it to upgrade to the MFPI injectors - budget about $300 for that.

 

[Pinger]

Looking at the photos it looks like it could be weeping oil from the head gasket.
Presumably there are internal oil drains in the heads and at on the 'outer' sides of the heads. I don't know these engines well enough to be certain of that. The stain seems to be localised around the head/block interface.

It doesn’t smoke or seem to go through a lot of oil but does have a small coolant leak that looks to be coming from the front of the intake. Kind of hard to tell with the accessory brackets in place.

I have that also. Seems to be coming from high up and central (thermostat or manifold possibly). Not losing significant coolant or overheating and intend to remedy it with pending inlet manifold gasket change.

 

[Erik the Awful]

Looking at the photos it looks like it could be weeping oil from the head gasket.

In my experience oil doesn't leak upwards. It might spread around a bit, but from what the pictures show that's most definitely coming from the spark plug. The oil on the threads backs this up.

 

[east302]

Thanks for all the comments.

With the miles, some oil burning seems reasonable but I’ll just clean it up and start watching the level to see how much it is using.

I took off the compressor and got a better look at the coolant leak. It’s at the front corner and block seam, some coolant was pooled in the valley between the intake and the driver valve cover. I’ve done the gaskets on my other two trucks so I guess this one’s getting the treatment this weekend.

The plan is to let our son drive this until he’s out of high school and go from there. If it was my daily driver, I’d probably be looking at a crate engine down the line.