Sanity check - "blown" head gasket
 

I've had my 03 4.6 SE7 for five years or so now, and it's been a fairly good car for the $2,000 I spent buying it. It had a paint blemish, sagging headliner, broken sunroof drain and the three amigos, all of which I fixed in short order. Other than that, it had 70K miles and ran pretty well. It has 90K on it now and I have the heads off to fix a problem I'd been ignoring since I bought it.

The car has always used a bit of coolant, but it was easy enough to keep up with it by watching the overflow tank. I replaced the long plastic pipes early on, and also the overflow tank and cap as I repeatedly thought I had found the leak and then had not. I replaced the upper hose assembly most recently.

Over the winter holiday, on the drive back from my brother's place, I noted the temp gauge at about 2/3rds towards "H" as I was getting on the freeway. The gauge has always just gone up to halfway and stayed there, didn't matter if it was 0F or 100F outside. Anyway, I'm eyeballing this, thinking I need to find some water when the gauge went back down to halfway and stayed there. "Hm" I thought. I had about 20 miles of freeway to get to the ferry back home, so I figured I'd just watch it and be prepared to bail if it started moving again. It did not. I stopped at the first fuel station after exiting the freeway and peeked, and yep, no coolant at all in overflow. Gas stations no longer have water as a service item in the lot, so I went in and bought $15 worth of plain drinking water (a gallon in about eight bottles) and put that in, as I was only about 15 miles from home, including a long ferry ride with the disco not running.

I got home fine, though the temp gauge did start moving up again for a few seconds on the road here on the island. Went back down again, as before, and never got more than 2/3rds up gauge.

In my shop, I took a peek around and discovered the top radiator tube had ballooned to many times its original diameter and in the process had pulled itself out of the end tank, so that's where all the water went! But, I was thinking, how did it over-pressure enough to do that? Shouldn't the pressure cap have released the build-up long before that could possibly happen? (I have a new cap waiting now, obviously.)

The next day I filled it back up with enough water to get it up to temp to use my "block tester" to see if there was exhaust in the coolant when running, and it said there was...or it turned the blue test fluid yellowish-green, which seemed close enough to me. A blown gasket could explain having a lot more pressure in the system than you'd expect, I thought.

I had lots of other stuff to do and a lack of money, so it sat until last week when I finally started taking it apart to do the head gaskets. However, when I got the heads off, there was no obvious signs of a blown gasket...no steam-cleaning of 1,2, 7 or 8 (or of the center cyls, either), no breaks in the head gaskets, no obvious cracks or other issues. No "mayo" in the rockers or anywhere else, the oil looks OK (aside from needing a change). Someone has been in here before; there was a broken bolt in the A/C bracket, a few hand-tight nuts on various minor brackets, and both heads have the number "20" written on them in paint marker, which I don't think is a factory practice. Perhaps they were surfaced 20 thousandths in a machine shop sometime in the past? Who knows.

I've cleaned the heads up and according to my precision straightedge they are both absolutely dead flat. I have not pulled the valves, but a cursory inspection suggests they're ok. The block itself looks fine, though the valley seals and both rocker covers were leaking oil, so it is all pretty grimy.

One curiousity: Is it common for 4.6 engines to have their compression ratio engraved above the engine number on the left side of the block? Mine has "CR: 9.37:1" right above the number.

Before I put this all back together (I have the head gasket kit from AB, a new thermostat, new lower hoses, new thermo heater plate and hoses, new rad cap, new radiator, new tensioner and idlers, new belt...) is there anything else I should check that might have precipitated this incident?

Here are a few photos, if I can get them to work:

https://cimg5.ibsrv.net/gimg/landrov...bd13e3336f.jpg
Just getting underway. I took battery/toolbox out because it's easy and less stuff is better. Same with coolant tank.
https://cimg7.ibsrv.net/gimg/landrov...d639469c91.jpg
Time to go underneath to get exhaust manifold bolts. Supervisor napping on his bed behind.
https://cimg0.ibsrv.net/gimg/landrov...bac7cc46d8.jpg
Right side bank with head off. No obvious issues here.
https://cimg7.ibsrv.net/gimg/landrov...495f359de0.jpg
Left side essentially the same...
https://cimg8.ibsrv.net/gimg/landrov...6f14f71d12.jpg
Heads and gaskets as they came off...dirty but unremarkable
https://cimg0.ibsrv.net/gimg/landrov...68752c554c.jpg
They cleaned up OK. Lots of work, mind.
https://cimg7.ibsrv.net/gimg/landrov...97b1fa3898.jpg
Block is getting cleaner, too. Still have to tackle right side.

Thanks for any insights!

Based on what I see I think you have a cracked block/liner on cylinder #6 unfortunately. Notice it has a large clean area on top of the piston. That coupled with the known gas in the exhaust and the no obvious HG blow are the signs. Recommend you pressure test that block before you invest time and money in to putting it back together. Also, if you are going to keep the truck you need an ultragauge or some other type of gauge to monitor engine coolant temperature, the factory gauge is programmed so it does not move until engine temperatures reach 230 degrees and by then it is too late. Also recommend you read this post on pressurized cooling systems https://extinctmotorsports.com/the-e...s-10-min-read/

Listen to Extinct. He is the guru of disco cooling systems.

Thank you for the reply. I'll examine #6 more closely tonight, but my impression was that said piston has white deposits on the top (like you sometimes see on lean-running spark plugs), not bare aluminum, showing. I'll take a closer look, and see if I can figure out how to pressure test this in its current state. If the block is cracked, that's it for this machine, I don't have budget nor desire to dump new engine money into this. (I like the car but it's my daily, not a passion object for me.)

I don't know what normal wear looks like on these motors, but the cylinders still have their hone marks all the way around in every bore. Was a bit surprised, being used to old Jags and MGs where 90K miles would almost invariably have had "lips" worn at extent of swept surfaces in each hole.

These engines typically go 275k plus without significant wear. You can pressure test with block off plates on the engine block but it really needs to be hot when you pressure test it. Best done out of the truck. You can put the 4.6 crank, rods, and pistons in to a 4.0 block, 4.0 engines go for about $650-800 with relatively low miles. Good luck. Truck looks to be in otherwise good condition, probably worth about a grand with the engine apart.

#6 is just as black and grimy under the light-colored stuff as the rest of the bores, after a quick visit with a brass brush. Doesn't mean it's not junk, but it's not been steam-cleaned. The head in that bore also looked like the others, FWIW.

I will be an outlier here put back together,you have the parts anyway so it is just time. The worst case you find out the block is indeed cracked, best case the problem is corrected, but you have been running at over 230F for along time and that can be rough on these engines. I would put a full bottle of coolant dye in the system, if you have a cracked block it should show at the tail pipe after a few days.
Also replace the expansion bottle cap, and check the overflow line for blockage.

Kinda late for this now, I know, but did you perform a cooling system pressure test before concluding the head gaskets needed to be replaced?

Yes, I know that replacing the headgaskets is something of a "rite of passage" for DII owners, but without a cooling system pressure test you're just guessing.

And BTW, I am completely jealous of your two-post lift.

I did not test the cooling system pressure. I figured with the ballooned rad it was definitely over-pressured, but should have thought about doing a test, for sure.

I moved in here over a decade ago and it took 10 years of watching CL for something I could afford, to grab the lift. I live out in the sticks, so by the time good stuff hits the nearest CL, someone closer usually beats me to it. This one is a USA-built Benwil made in the early 1990s, nominal 7000lb capacity. Guy I bought it from had a big service business and modern car dimensions (width and weight) forced him to replace all of the lifts in his shop, so he had five of these for sale at a grand a pop, which is pretty good for my area, price-wise. I got the last one. Managed to haul it back in my equally old, high miles F250. Loading, unloading and setting the lift up was a challenge, and I'm just fortunate the cheapskates who built this building poured six-inch floors. But it has definitely been a nice addition, given my aversion to lying on the floor (lying isn't a problem, it's getting back up that's a bear, I got old when I wasn't paying attention).

A machinist friend took a look at the photos and thinks both 7 and 8 were blowing into the water jacket, not yet for long enough to take the gasket with them. So that's something. (He said back in the day his shop was doing 30 pairs of LR 4.6 heads a month, including more than a few straight from the factory.)