1998 ES300 308.5k miles.

During my recent big top end overhaul working on the center valley plate and knock sensors I found coolant crust along the head gasket seam on the inside of the V. I also discovered greasy oil residue on the outside of the block below the exhaust manifolds where the head gasket is.

Are these signs that my head gaskets have failed?

I’ve been noticing a mysterious coolant level drop for years, hence why I resealed the center plate after seeing that crust.

I also started to top off the engine oil between 5000 mile oil changes, adding about a quart at the 4000 mile mark.

Checked compression while everything was apart. 1. 225psi 15.5bar

2: 235psi 16.0bar

3: 210psi 14.5bar

4: 228psi 15.8bar

5: 220psi 15.3bar

6: 235psi 16.1bar


Here is the area around the oil filter. You can see the gasket has split along the edges and greasy residue is seen below it.







Here is the coolant crusty around the center valley plate.







After cleaning everything up and resealing the area.

 

Hello,

It appears that the oil residue appeared from valve cover gasket at some point, since I am not sure what could result in a head starting to lose oil short of a clack in it, which will definitely show up with the compression test. The stain seems to have been there for quite some time, so for now, try cleaning it off as best as possible and see how soon it will come back, if at all. Unfortunately, with this kind of mileage, oil consumption is inevitable, yet a quart for 4,000 miles is still within good reason.

Coolant stain is a bit more tricky, I wonder if it could've been a result of leaking center cover in the block, or the coolant hose itself, which those are prone for. The most loaded parts of the head gaskets are the ones near the cylinders themselves, both in terms of temperature and actual load, so it seems unlikely that the gasket will crack somewhere on the edge, leaving the cylinder completely intact and functional. Now that you resealed it all, you can use a borescope camera to check on it once in a while, to see if those stains will appear again, if so, they may start showing where is it that they come from.

Hope this helps and best of luck!

 

You should wash your engine bay several times a year get rid of the salt build up. Also makes leaks much easier to find.

 

I have a borescope camera so I will try investigating under the intake and I also cleaned off the oil residue to monitor.

The bypass hose was 11 years old but not leaking yet. I was thinking it was the center plate but it seemed kind of high and too close to the head/block seam.

I had a major problem last fall that I thought may have caused some long term damage. When I swapped out the B1S1 and B2S1 Air/Fuel sensors I accidentally broke one of the harness signal wires on Bank 1. I went for an extended test drive before I figured out the problem. The car misfired really bad on Bank 1, overheated the spark plug wire on the rear center cylinder 3, and carboned up all rear spark plugs. So I was worried when the compression came back a little lower on Cylinder 3 than the rest during the overhaul. However that doesn’t explain Bank 2 oil leak issues because it ran pretty well.

In addition, I have an active drip from the transmission input seal that’s getting on the back of the subframe and exhaust mount. So I’m already thinking of pulling the engine and trans to do a complete reseal of all the problems spots: rear main, trans input, head gaskets, and axle seals.

Cleaning the engine is also a goal of mine. The oxidation is pretty intense as the car lives outside in the Northeast.