4.0 ohv coolant contamination/loss

[cp2295]

Hi everyone I have a 99 ranger 4.0 ohv 5 speed that I've noticed using coolant the past few months. This past week I've noticed that its oil contaminated and smells strongly like motor oil, still is green but definitely has motor oil in it. There's no coolant in the oil-no milky residue and doesn't smell like coolant. Where is the source of the leak? Is it most likely a cracked head and how can I tell?

The motor also rattles above 2.5k Rpms while in gear under light load so I'm wondering if it's time for a rebuild (think I got low oil psi). Has done it ever since i swapped the motor in 20k miles ago, just noticed this coolant issue now tho.


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[RonD]

With an automatic I would say trans cooler but that is out.

You can test for cracked head or head gasket leak with a Latex Glove, or a balloon or a condom

Called a Glove test
Remove rad cap
drain a little coolant out, so it is down 1/2 to 1 inch
remove overflow hose and block that port in rad
place glove over rad opening and seal it with rubber band or ?? wire tie, or use balloon or condom

Disconnect coils, or pull Fuel Pump relay, you want a no start

Crank engine and watch the glove, if it bounces then you have a leak from a cylinder to the cooling system, i.e. cracked head or bad head gasket

If glove just lays there then you don't.

If it does bounce then remove 1 spark plug from a cylinder and crank again.
repeat until glove stops bouncing, last spark plug removed was from the leaking cylinder, put plug back in and crank engine again to confirm.
Not that this last step helps you, but it can be good info to have when disassembling and inspecting

 

[cp2295]

Okay is there anyway to tell for sure where it's cracked, or will the plug/glove test just get me close? Then I'd have pull apart the motor and inspect


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[RonD]

Read post all the way thru.

You can tell which cylinder is leaking, but no you can't tell if it is a crack or gasket issue until it is apart.

 

[cp2295]

Okay yeah I read it all the way just wanted to be sure I wasn't missing anything, just realized today I got water In the oil so no more driving the rig. Luckily I got another rig to drive for now, and luckily it didn't overheat and get a knock in that time-knock on wood hopefully it's just a head gasket or if it's a cracked head I won't be too concerned there's a billion expos in the junkyards near me. $40 a head with valves-not bad huh?


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[cp2295]

Well Ron your test was a success-the #6 cylinder is my offender glove stopped bouncing when I took that plug out and started bouncing again with it in. I should of known it was giving me signs that cylinder was getting screwed, it kept fouling the #6 plug every 5000 miles


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[cp2295]

Got the head pulled can't find any real obvious cracks and the gasket isn't blown... Maybe the heads warped idk, gonna take it to the machinist have them check it out magnaflux it and all that


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[cp2295]

The #6 piston looks cleaner (steam cleans carbon off real good I hear...) so that makes me feel more sure of my findings also I saw a little antifreeze in the cylinder could be residual that drained off the head


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[RonD]

Yes, piston top cleaner means leak.

Look close at the metal ring on #6 head gasket, if there is no breach there then look between valve seats on #6, just a slight line will mean a crack.
Yes machine shop can pressure test heads.

get the head gasket kit, it will come with new valve guide seals, then drop them off at machine shop they will usually install them for free, well included in final price so not much added.
If you have a valve spring compressor then never mind

 

[cp2295]

I do but man I sure as hell hate putting valves together! Tho I've done it on 3 sets of heads it still is a pita and time consuming!

It's not much cleaner but much lighter colored than the other 2 Pistons. And whereas the other pistons are totally covered with carbon the #6 has spots of bare metal

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[cp2295]

I wouldn't think the gasket would be screwed, it has only 20k and it's a fel pro but I could be wrong.


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[cp2295]

Just curious the only way I could have contaminated coolant and oil, and also have coolant in the #6 cylinder is an issue with the head gasket or a crack in the head?

It's unlikely the block is cracked right? The only way I could see the possibility of it being a block issue is a crack In the cylinder wall.. But then I'd have way bigger issues/symptoms I feel.


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[RonD]

For coolant in the oil and "bouncing glove", it would have to be gasket, cracked head is just coolant in cylinder and "bouncing glove".
Cracked block usually just has coolant in the oil, and no "bouncing glove"

 

[cp2295]

Or warped head too for the bouncing glove?


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[RonD]

Warped head would be a gasket leak, you would see where gasket was leaking by less pressure from head pressing down on gasket do to warping.

Bouncing glove is when some of the cylinder pressure on that cylinder's compression stroke, 150+psi, is forced into cooling system passage, that adds pressure to cooling system and glove inflates.
This bouncing requires the metal ring on that cylinder's head gasket to be breached.
Cylinders are surrounded by cooling passage holes from block to head, so once metal ring is breached the cylinder compression forces softer gasket material away from head surface or block surface and usually encounters a cooling passage, that is when problem starts.
The cylinder compression forces pressure into the cooling system but on that cylinder's intake stroke it also pulls coolant into the cylinder, why the glove bounces and just doesn't keep inflating, on a running engine(900+psi in firing cylinder) glove will stay inflated.
Running engine has -18psi on intake stroke at idle(intake vacuum), so more coolant is sucked in, and if rad cap is on, then there will be +14psi to push even more coolant in.

As the head gasket deteriorates even more from this pressure it will often encounter oil drain in head and coolant will get in the oil, depends on where original metal ring breach occurs, there are also 3 oil passages in the 4.0l head that could also be breached.
Coolant in the oil is not that common on head gasket breaches any more, it certainly happens but the newer gasket material and designs mean you can have a bad head gasket without coolant in the oil.

Cracked head is the same as above except there are no oil passages in the cooling system, so coolant in the oil is unlikely, I suppose with a bad rad cap the pressure in the cooling system could exceed 50psi and intake gasket could breach and send coolant into the gallery and then oil pan, but I would expect a rad or heater hose to pop before that.

Cracked block lower in cylinder wouldn't have the pressure to bounce the glove, but could still suck coolant in on intake stroke, and could allow coolant to leak into oil pan when engine was off depending where piston in that cylinder stopped.
Cracked block high up in cylinder could bounce the glove but shouldn't leak coolant into oil pan because piston rings would stop it for the most part.


Head gasket breaches are not obvious but you can usually find the spot by running fingers around metal ring and feel for any difference.