Gasket Issues?

[RonD]

No to the aluminum head, whole new set of problems when running a bi-metal engine(aluminum heads and cast iron block).
You would need to run a MLS head gasket(multi-layer steel) and they don't seal very well unless head AND block are surfaced.
The benefit of aluminum heads are less weight, the draw backs are that aluminum heats up faster than iron so expands faster.
When car makers tried to do aluminum heads on iron blocks originally they had head gasket failures by the truck load, lol, the aluminum heads were "rubbing" through the composite head gaskets every time engine was warmed up and then cooled off, so 20k-30k of driving could see leaking head gaskets, 60k was consider the lifetime.
They switched to MLS gaskets so aluminum head would "slide" as it warmed up and cooled off, this worked but .........they had a lot of issues with cold sealing, MLS gasket would leak when cold and then reseal when warm, the cylinder didn't leak but coolant did leak out the edges or into the oil,
They fixed this by better machining of the heads and blocks, tighter tolerances.
DIY replacing of an MLS gasket can be fine, but can also go badly depending on the condition of the block surface.
They do make graphite coated composite gaskets, these enable "sliding" more than "rubbing", but "rubbing" can still be an issue, these gaskets are better for DIY because they seal better on an un-resurfaced block, they are more forgiving.

So you could go with aluminum and use a graphite gasket but I wouldn't.


The head cracking is a know issue, maybe common was the wrong word.
A failed head gasket is more likely when you have a cylinder leak, but I would have the heads pressure checked, for a crack.

 

[Automobilie]

So get a new iron head then? I can't really get the block taken out, but do I need to get teh thing taken in and done anyways? I sent it to a shop to get those bolts out so should hear back in a few days.

 

[RonD]

So get a new iron head then? I can't really get the block taken out, but do I need to get teh thing taken in and done anyways? I sent it to a shop to get those bolts out so should hear back in a few days.

You sent in the heads?
So did you see any cracks between valves?
Or did you see where head gasket was leaking?

Yes, if head is cracked then regular 4.0l head

 

[Automobilie]

Got the truck back from the shop, heads and manifolds are off. i'm at school, but I'll try and remember to post pictures of the head gaskets. There was some white buildup on one of the valves, but no visible cracks yet. Heads are at a shop to get cleaned and checked, the gasket doesn't look exploded though :/.
So how would i be able to check for a block crack short of pulling the engine out?

 

[RonD]

Cracked blocks usually only happen from freezing, and even then it is pretty rare.
On a new engine it could be a casing flaw but once there are 10,000 miles on the engine a flaw like that would have shown up.

A head gasket leak can be pretty hard to see on the gasket itself.
The cylinder "with white on the valve" would be the best one to look at, feel the metal ring on the gasket, you are feeling for an imperfection, it will be near a smaller hole in the gasket which is a normal water passage.
A head gasket failure comes from the cylinder and moves to the water passage, the cylinder has 400+psi when firing, the water jacket has at most 18psi.

So check the metal cylinder rings on the gasket.

A head gasket "blows" from overheating, this happens because of low coolant level or from running engine to lean or from "pinging"
To lean of a mixture increases cylinder temp
"pinging" increases cylinder temp
Low coolant......increases cylinder temp

Metal expands when heated, at "normal" engine temps the head gasket takes up the slack between the two pieces of metal(head and block), when temp goes to far above "normal" the metal ring can be compressed between the head and block more than it can rebound from, so 400+ psi pushes out at that spot.
Since cylinder's metal ring is surrounded by coolant passages that's usually the where you will notice it first, 400+ psi pushing out coolant into overflow.
There are also a few oil passages in the head gasket, if the 400+ psi continues to push into the gasket material you will eventually end up with a connection between the coolant and oil, so "water in the oil" milkshake.


A quick over heat usually won't blow a head gasket(unless you have aluminum heads), it's the "driving it home" overheated that will bite you in the butt.
Better to let it cool off and spend 2 hours driving that 15 mins home than spending 9 hours and $$ on a head gasket.

 

[Automobilie]

http://s662.beta.photobucket.com/user/Automobilie/library/

Should have a bunch of engine pictures

 

[RonD]

yes, I would say where you don't see the rusty stains would be the most likely spot for the breach, gasket has been "steam" cleaned on that water passage.

 

[Automobilie]

So they found a crack between the water jacket and the valve cover, which is odd beacsuse there wasnt' coolant in the oil :/
Went ahead and had him order in two new heads and swap in the valves for $550. Supposedly they're 'thicker' and should be in tomorrow.
Also didn't find a steam cleaned area on the heads or gasket. So hopefulyl there isn't a block crack. What should I use to clean off the block before reinstalling everything?

 

[Automobilie]

Got the new heads onwith new gaskets. Havent' heard the knocking in the heater core yet, but the engine still heats up and then drops like before. We're gonna try a Radiator flush, I guess it's pretty dirty looking, so we'll see what happens after that.

 

[RonD]

I would also by-pass the heater core to see if that is causing the up and down temp gauge, it can on some designs.
Just run 1 of the heater hoses to the "out and in" on the engine, or use a coupler and two hose clamps to put the 2 hose together, which ever is easier.

There is an old test for a partially blocked rad, but you have to remove the rad.
With rad out put it in the direction that has the cooling tubes running up and down, some rads have tubes running up and down others side to side.
If rad is on it's side then put rad cap on
Now put your hand over the lower hose outlet and fill the rad with water using the upper outlet
Stop filling when full
Now remove hand over lower outlet, water should gush out rad should be empty in a second or two
tilt rad slightly forward to make sure all water is out

Now the test.....flip rad upside down from its current position, if ANY water comes out it could ONLY come from blocked tubes.

 

[Automobilie]

Ok, so a final update. It all seems ot be working fine. The temp guage stopped fluctuating and I haven't lost nay coolant last time I checked.
We got the new heads on since the old ones had a crack in them. New gaskets, etc. Got it all back together adn still was heating up. My dad said the radiator looked pretty dirty to him so we ran some cleaner through it. An hour with the cleaner in tehre it stopped fluctuating! Ran cleaner through it a couple times, drained it, flushed out the heater core, and 4 days later still hasn't been bouncing around! So for anyone in the future try flushing the radiator first (I had before a couple years ago, but it was a 15 minutes flush, this was a 4 hour clean). Although the crack in the head would've been a problem down the road. The odd thing is the crack was between the water jacket and the valve cover, not into the block, so I'm still a little nervous about one in the block wall, but right now good to go! Thanks for all your help guys!