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· Registered
151 Posts
Discussion Starter · #1 ·
Are you aware about stock OEM heasd cracking on Magnum engines and fix for it? What are symptoms of the "slightly" cracked head?
My Magnum is not behaving! I thought, it may be blown intake belly pan gasket. Took the manifold off-it is OK! I am puzzled.

Apparently there are "new" heads on the US market, sometimes called "Iron Ram". Do you know what is a difference?
The only information I run into is an info from one of the engine rebuilders:
"All of the magnum heads are prone to cracking between the valve seats because they are induction hardened. Our Iron Ram heads have pressed in hardened seats that eliminates this problem. About 50% of the factory heds we see are cracked.

The new heads #4666 and the 4668 are imported from "Down Under' Australia. They are an aftermarket part. Much better than factory, both in performance and quality."

· Transmission Man!
3,519 Posts
I run a 180 degree thermostat to hopeful help prevent it.

· Registered MOPAR User
9,389 Posts
Heads cracking are due to not keeping the coolant levels proper, serp belt failure or water pump failure, And yes a 180 TS will keep you from overheating unless you have an underlying problem.

Have you pulled your plugs yet? That will be your dead give away on cracked heads

· Registered
151 Posts
Discussion Starter · #5 ·
My Problem

Mystery of disappearing antifreeze and other funny things. Many Dodge owners complained about this phenomenon at and other blogs. Unfortunately, it happened to me, too. I need your experience and the brain-power to solve this mystery!

My truck: 1999 RAM 1500 SLT, 5.9L Magnum, code “Z”, 96,000 miles, Fastman TBI, ACCEL variable flux super coil, K&N, 8mm wires. Used daily, highway.
Couple weeks ago, (33F outside), my coolant temp gage chime rung after driving only a mile. Gage went up to 260 F. I stopped the truck, checked coolant level in the radiator overflow tank. It seemed OK. With a rubber glove I partially turned the radiator cap. Some air bubbled out. When I started the engine, temp gage went down to 160 F, then raised to 180-190F and started cycling normally. For the rest of the trip (100 miles) the temperature did not go over 200F. Two weeks later, the same s… happened, except I “lost” quart or so of coolant. I replaced it. I replaced the radiator cap. Everything was “fine” for a couple of days. Than, it happened again! This time, I “lost” 2+ qt of coolant. Power and acceleration seemed to be good. No idle change, no sputter. There were no leaks or puddles under the truck and no wetness in the engine compartment. NONE! I drained the engine oil; there was no antifreeze contamination, just “pure” oil.
Next, I run a cooling system pressure test. With engine cold, it dropped from 22psi to 18psi in 10 minutes and… stayed there. Gage showed 18psi after 2 hours. Now, I am totally confused! Why it did not drop any further? I de-pressurized the system and started the engine with the radiator pressure gage attached. After 10 min of idling temp gage on my dash started going over 200F. At the same time radiator pressure did not go past 6 psi. No apparent loss of power, not smoking, no hesitation.
I pulled all plugs. Looking good. (With a high energy coil voltage arch they can not look bad!). I decided to run a compression test.

cylinder 2 4 6 8
pass side dry (psi) 115 125 110 135
wet first puff 115 125 125 130
wet @4rev 130 140 140 145

cylinder 1 3 5 7
driver side dry (psi) 135 105 120 110
wet first puff 120 140 120 120
wet @4rev 150 145 125 130

Cylinder 3 & 5 look suspicious (?). Any thoughts? What might have happened?

I took the water pump off; looking good. Next, I took the intake manifold off.
The whole underside was covered with 1/8 to ¼” black hard baked sludge deposit! It was thicker & bubbled @ the front, by the thermostat.

All injectors, but all, on the Driver side, Cyl 1,3,5,7, exhibit very small bright “wash off” areas, perhaps, narrow spray cone angle, (or low air velocity?).
All injectors on the Pass side, Cyl 2,4,6,8, have large bright “wash off” areas, extending towards the head ports, indicating much wider
spray cone angle or larger air flow. Any ideas why?

Why such a difference? Would it have something to do with different air velocity @ Dr vs Pass cylinder bank. ( Fuel rail pressure was OK.)

Pan gasket was bulging & protruding outward between cyl 4&6 ports, passenger side. There were no gaps; gasket was still sealing both parts!!!
In two places gasket was marginal, but still had solid 1/8” overlap. Judging from impressions on the gasket and a pan surface, there were NO leaks.
(Pic shows gasket broken, I bumped into it). I am replacing it with Hughes Engines aluminum belly pan!

Now things are getting very interesting.
Upon the belly pan removal there were puddles of oil inside at the bottom of (now inverted upside down) manifold.
Inside surfaces of cyl 1,2 and 5,7 runners had a continuous oil coating as far as I could see the bottom. Cyl 3 runner had some residual oil film.
Cyl 4, 6&8 runners were SQC (squeaky clean)! Picture below, upper left.

Inside surface of the belly pan shows oil splatter area under the cyl 5 and 1,3 runner inlets. Take look at this picture. All on the passenger side!
(Also: see pic showing 1,3,5,7 injectors minimal wash off pattern. )

What would cause oil splattering under the runner inlets? If the kegger was tight, where did the oil come from?

Pic above: 5,7 runner inlets and a splatter pattern under. (Itried to post some pictures, but it did not work well)
Pan area under cyl 2,4 and 6,8 runner inlets, is clean, showing a bare metal!

Cyl 5 head port shows suspicious dark discoloration area.

pic below: 1, 3 ports look darker than 2,4 or 6.8.

Here is 2, 4 port for comparison, below.

At this point, you may ask what antifreeze has to do with all of this? I dunno- is my answer. I am digging deeper and deeper. Still, no antifreeze. It disappeared!
Below, couple pics of the gasket surface @ heat passages. May be you’ll find a clue.

Did miss anything? I hoped I don’t have to remove heads, but… you tell me what to do next.

Thank you for any opinion or advice.

· 4 Wheel Power Disc Brakes
5,837 Posts
Although #3 and 5 are suspicious, # 6 has a larger increase with oil, cranked over 4 times if I read correctly. You might have scored cylinder walls from a cam that is chipping.
As to the coolant leak are the freeze plugs all good, including those in the back of the block?
Were are your pictures at... I don't see them in this thread.
It sounds as if there are multiple problems, Excess oil in manifold and resulting discolored ports, coolant loss and uneven compression.
Oil in the manifold could be from blow-by if the rings or cylinder-walls are damaged.
It doesn't take a large leak to loose coolant.. In fact many are small (pinhole size)and usually a result of debris in the cooling system covering them and then being pushed aside causing them to happen and cover up again, especially if the system is dirty.
Also check the radiator closely for leaks.

· Registered
151 Posts
Discussion Starter · #7 ·

Thank you very much for your response B-3000.

I had pictures embedded in a text. They disappeared when pasted to this web. I am working on this. I was told I have to use "picture bucket" feature on this site-not quite sure where is it located.

· Registered
54 Posts
To let you guys know yes they are prone to cracking. It is more common on the Magnum Heads. The reason is because Dodge went to a thinner casting in the cylinder heads from the factory. LA heads off any of your small blocks will have the same problem just not as common but, almost. They like to crack between the intake & exhaust valves. Engine Quest has a set of heads that will remedy this problem. They reinforce the area prone to cracking. I think a set will run back $800 though. But, if you want shell out money for aluminum ones the Edelbrock heads are the way to go. They are pricey but, they won't crack like the cast will.

· Registered
151 Posts
Discussion Starter · #10 ·
Heads from downunder

I got a set of beefed up aftermarket auatralian heads for $540 from J and C Head Exchange @ ebay stores. Brand new with valves and springs installed! They have heads, rockers, gear drives, etc, at very reasonable prices.
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