1996 Sport - 4.0 OHV Coolant Leak

[mediaman67]

Hi All

Got a 96 sport with the 4.0OHV - I have a coolant leak somewhere and I can't seem to find the source

I notice it at idle, and it comes streaming out behind the T-Stat Housing, under the sensor that is there, but it's not around the 3 bolt gasket that is there... like behind that part...

The truck does not overheat, and I get no white smoke, etc, so I don't think it's a head gasket...

does the coolant go places under pressure outside of the engine? - I know the bottom hose is good - had to pull that to drain the system and I did a flush while I was at this - seems like it might have made it worse after doing a flush... it needed it though!

when you look under the car when running, there are several places where it's just a constant stream, so it's a good sized leak wherever this is...

Again, engine has no miss, doesn't overheat, and no white smoke...

Thoughts?
Thanks

 

[96eb96]

Possible Lower intake manifold gasket. Quite common.

 

[mediaman67]

Wow - ok, that would make sense - didn't think they leaked that bad though... I do see it wet just above the exhaust manifold on the drivers side (above the spark plugs there... steams when running from there, and worse when you shut her off - other side does too.

It makes sense because it looks like it's leaking almost in 3 places, guess when these fail, they FAIL.

anyone ever done this job on a OHV 4.0L - is it not worth it on the labor? I pull the TB, and the top of the intake (plastic)? Then the intake itself? I wonder what the book time is on this?

Thanks all (esp 96eb96)

 

[96eb96]

I had a freeze plug leak too. You may have multiple leaks.

I put in a good sealer (K-seal) and it is fine for months. Others used it too. I know it is an additive but if you cooling system is clean it will also protect you from cracked heads as well, I think I had that issue. The intake gaskets are a bit of work but doable. Another option is taking off the upper, and re torquing the lower bolts to spec. My lower was not leaking, but the bolts needed about 1/2 turn (with a torque wrench).

I mean, these trucks are rusty, and can even get rejected at a State Inspection. I can't justify too much work for it anymore.

 

[mediaman67]

I thought it was a freeze plug at first actually....

So, you used K-Seal and you liked that product? Funny it wasn't leaking that bad until I did a system flush with the prestone soap, and it did a good job, but now it's leaking a lot worse... maybe the crud in there stopped it up some?

Yes, Im realistic - I know it's not going to last me 4-5 more winters here, but I was hoping to get one more out of her - makes you cry when you see how rusty it is under there... the rockers are almost all bondo now...

Thanks

 

[96eb96]

I thought it was a freeze plug at first actually....

So, you used K-Seal and you liked that product? Funny it wasn't leaking that bad until I did a system flush with the prestone soap, and it did a good job, but now it's leaking a lot worse... maybe the crud in there stopped it up some?

Yes, Im realistic - I know it's not going to last me 4-5 more winters here, but I was hoping to get one more out of her - makes you cry when you see how rusty it is under there... the rockers are almost all bondo now...

Thanks

Very possible that the flush did that, coolant also contains silicates (sand) that can plug tiny leaks.

Yeah, I know what you mean, it is hopeless at this point. All it takes is a hole in the frame to fail inspection and it is gone. And I replaced things like shackles, brake lines, steering lines, etc. Doubt even with all the care it is worth $1000, but even if you get a few years out of it vs something new you are ahead. A new Explorer note is $600/mo + more insurance, etc. All the body on frame explorers around here (2010 down) are rusted hulks, I've looked at many.

The K-seal worked fine for me, I have no overheating. I am not going to invest at least $600 in heads and my time to fix it in that shape.

I installed it into the coolant sensor hole just to be sure it don't hurt the radiator. Goes right into the block and dilutes with coolant. Honestly, I wouldn't drive without it now looking at those freeze plugs. Some cars even specify sealers during coolant service. If it was a no rust Arizona truck, that is another story.

 

[FijiBill]

Below is a pic that shows the lower intake manifold gasket (green) that surrounds the 4 narrow coolant crossover ports (near the big bolts) in the lower intake. The 6 larger ports surrounded by the gasket are the air intakes for the cylinders.

The coolant crossover ports can leak coolant to the outside and/or the inside of the engine. Outside is not a big deal, but inside is a problem and you should check your oil level isn't rising from contaminated coolant which will destroy your bearings.

Removing the upper intake takes the most amount of time. After that you only have to disconnect the fuel line/injector harnesses, tap off the valve covers, pry up the aluminum lower intake, clean, and reassemble.

 

[mediaman67]

yes, the big worry is internal leakage... I hear that. I will check the oil tomorrow and see what's happening there.

I wish I had a definitive answer to this, but if this seats right behind the T-Stat housing, that is the problem - I can watch it stream out in that area... I am assuming that the T-Stat housing is part of the intake manifold? - like if you removed the intake, the T-Stat is right there in the front, correct?

how possible that the gasket is leaking in more than one place? would these fail all at once like that, or just a single spot like a head gasket would normally?

Im betting a freeze plug too, because even with the engine off, if I try to fill the radiator, it will eventually run out, and onto the driveway, and I know it's not a bad lower hose (doesn't leak there, but somewhere back farther.

Thanks to all once again

 

[lobo411]

These lower intake manifold gaskets almost always leak externally rather than internally. You'd know it if you were leaking coolant internally...your oil would be milky.

My bet would be it's the LIM gasket since they tend to fail around 150k. I'd probably replace it, but you might want to inspect:

1. Upper radiator hose at the water outlet for a pinhole leak, bad clamp, or corroded water outlet
2. Thermostat housing for a proper RTV seal or corrosion
3. Heater hose at the water pump (check for the same things as #1)
4. A leak at the temperature gage sending unit or engine coolant temp sensor

I'd get the gasket and plan on replacing it, and I'd inspect/replace the above as needed since you're likely to have to do that anyway.