Gen 3 Montero - I think I have a blown head gasket

[MrGideon]

Hello, I bought my Montero about 6 months ago and have driven it thousands of miles, its seems to run good and the idle is smooth, and hasn't given me any trouble so far. It's a 2003, with 85000 miles. I was checking all my fluids yesterday and opened the radiator cap to find a white foam, to my horror. The coolant is black/dark brown. The overflow is coated in what appears to be an oily residue. Obviously my first thought is that I have blown head gasket. The car still runs and drives fine. I checked my motor oil, its about half way from the low and the top mark and I had it changed 6 months ago, so that doesn't seem like excessive consumption. The oil looks good too, its amber, there is no foam or sludge coating the inside of the oil fill cap, or any of the springs. I checked the transmission fluid and it looks good too. So I only have one symptom of many for a blown head gasket. I'm in the process of flushing my system, drained it, added distilled water and a radiator flush fluid, drove it around, drained it again, and the liquid was still very dark, so I will added more distilled water and will drain it again in a couple of days.

I guess my question is, do you guys think this is unquestionably a head gasket leak? Is a head gasket on a 3.8 liter montero something a home mechanic can do themselves? I have another car if it is a two weekend job. Or is this the kind of thing that you need to very experienced/trained on?

Thank you.

Gideon

 

[dos531]

It could just be sludge in the engine. Try running a thermocure flush

 

[MrGideon]

I'm starting to think its the oil cooler.

 

[nwoods]

I don't have a helpful opinion about the troubleshooting aspects. There is a lively Montero group on Facebook that has been helpful to me in similar circumstances. However, doing the head gaskets is not too hard. The hardest parts for me were undoing the exhaust manifold(s) and the AC/pump. I think I was able to leave the AC compressor in place last time. Another hard part is the metal coolant lines into the back of the heads. There is not a lot of room to access those. Here is a photo of my 2002 3rd Gen torn down to the block:

More here if you are so inclined: https://nwoods.smugmug.com/Vehicles/Montero/3rd-Monty-Restoration/

 

[MrGideon]

So, I guess if I'm gonna do it's a good time to change the timing belt.

 

[nwoods]

So, I guess if I'm gonna do it's a good time to change the timing belt.

Definitely! I also send my heads out to get refurbished. Was about $150 per side, came back looking better than new. That fixes the well known valve seal issues also.

 

[ajm291]

I have an 06 montero and had the same issue that you're dealing with. Oil in the coolant, but nothing else wrong. The coolant in the overflow tank and under the cap of the radiator always had a layer of oil floating on top. My oil in coolant issue was minor, but troubling so...

I tore into it, removed the heads, leaving the block in the truck like in the picture from nwoods.

What I noticed was that the engine block had some pitting on the top surface between the oil and the coolant passages. The oil pressure is higher than the coolant pressure so oil was being pushed (through the pitting on the cast iron block under the head gasket) into the coolant. I cleaned everything up and used good old JB weld to fill in the pitting on the block.
I had the heads resurfaced and installed a new head gasket.

That repair was done 2 years and 20,000 miles ago and my coolant has been clean and oil free since the repair.

You'll need to clean the coolant system pretty well to remove the oil contamination. I reused my radiator after cleaning and flushing it out.