Coolant leak, front passenger side under alternator
 

Hey guys,

Did a lot of searching and most hits refer to leaky T-stat housings, but I don't think thats what the problem is here. (This is my son's truck and I'm just getting familiar with it so I can help him diagnose and repair the issue.)

Before we start tearing things down for an inspection, what might I look for that could be leaking at the front of the motor just under the alternator? I've checked the radiator and heater hoses and don't see any obvious leaks. The leak is definitely "before" the thermostat, since it leaks as soon as the engine is started and not only when hot/pressurized.

The coolant is pooling in the area indicated by this arrow inside of a large Torx head screw:

https://content.screencast.com/users..._15-22-05.jpeg

The leak is a constant drip while the engine runs (but does not appear to be dripping when off).

Do the heads on this 4.0 leak to the outside if there is a blown head gasket? (never seen that before...)

My plan is to pull the alternator to get a better view and thoroughly check all the heater hose connections and the metal pipes for the heater. Anything else common in this area that might be leaking?

Re: Coolant leak, front passenger side under alternator
 

Mine leaked in the same spot, it was the lower intake plenum manifold gasket and the coolant jacket is right there. If I can, I'll scan my build thread pages and link you to where I did the work. Can be completed in a couple hours providing you have all parts in hand.

It will stop leaking when the engine is off because the water pump is no longer forcing coolant through the upper passages.

Re: Coolant leak, front passenger side under alternator
 

Thanks! Anything that we should replace (preventive maintenance) during the tear-down to get to it? Truck has 210k but it’s been well maintained. However it still has s lot of the factory squeeze type hose clamps!


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Re: Coolant leak, front passenger side under alternator
 

OK so I just pulled the entire t-stat housing and I can't see any obvious cause of leaks on the housing. Unfortunately the residual coolant in the upper radiator hose dumped all over my work area, so I can't trace the source of the coolant, since now there is coolant everywhere...:(

Before pulling everything apart, we'd identified most of the puddling at location indicated by #1. But now I'm hesitant to replace the t-stat housing and button everything up without positively identifying the source of the leak... (and if I do, I think I'll go with the $80 aluminum version on eBay)

When you say "lower intake plenum manifold gasket" are you referring to the area where #2 is located in my photo? I didn't realize that there was a water jacket in the lower intake plenum, but I do see a collection of coolant lines that seem to connect to the heater and also run back behind the motor...

Also, btw, what is the hose called that connects the pipe at #3 to the top of the T-stat housing? Its a 90º bend, about 4" long

Thanks!

https://content.screencast.com/users..._14-17-28.jpeg

Re: Coolant leak, front passenger side under alternator
 

Argumentative at most, I like the squeeze clamps as I have the right tool for those.



http://s150.photobucket.com/user/Und...ml?sort=6&o=89

http://s150.photobucket.com/user/Und...ml?sort=6&o=97

If you see the front center upright stud center of pic. just below it is the water jacket that seems to become that popular leak.

You'll need:

• lower plenum gasket, FelPro is ok [just don't use their head gaskets IMO]
• intake manifold gasket - sometimes sold in pairs but you can often buy them single. There's two identical above the fuel rail and below it to the plenum. If you only remove the lower portion that connects to the lower plenum you can save the use of one gasket, also FelPro is ok.
• and preventative wise - it'll be a great time to swap the valve cover gaskets and tighten them and the I/M bolts to spec.

http://s150.photobucket.com/user/Und...ml?sort=6&o=92

http://s150.photobucket.com/user/Und...ml?sort=6&o=93



As for the T-stat 4" pipe.. I'd have to see a better pic. On my 93' OHV I don't recall that looking like that so much. but your intake setup is slightly different from mine but Valve covers to oil pan down should all be the same.

Re: Coolant leak, front passenger side under alternator
 

This spot here?

https://content.screencast.com/users..._14-17-28.jpeg


If so, there's definitely no evidence of leaking from the seam indicated inside the red circle, which I suppose is good news since I really didn't want to have to pull the intake manifold and VC gaskets. After 200k miles, a lot of the wiring looms are brittle and I just had having to move stuff around too much! :-)

Re: Coolant leak, front passenger side under alternator
 

Hey just wanted to follow back up on this thread. We replaced the thermostat housing, since that seems to be a very common problem. It looked like it had been done not too long ago (he's had the truck about a year so it would have been longer than that).

I called the local ford dealer and they wanted about $180 for all the parts. After reading about all the problems with Dorman aftermarket parts, we decided to go for the aluminum replacement unit from Austek but got it from ebay seller "bfoot58" ("Armadillo Auto parts") for $81 shipped.

Its a really nice unit and includes both sensors, silicone water pump bypass hose, thermostat, and all the necessary mounting screws. A complete drop-in unit. Tough to beat that deal.

In order to install it, I pulled both sensors and the upper t-stat housing, then slid it in under the intake and screwed it down , then plugged the sensors into their harnesses and installed them into the holes, then finally installed the upper t-stat housing. Very simple and it fit great.

The good news is that it doesn't leak any more, so that must have been the source of the problem, even though I could not see ANYTHING wrong with the unit we removed.

One other thing I noticed is that someone previously replaced one of the sensor harnesses so that both sensors are the "gray" body units (originally one is gray and one is brown and the connectors are different). For some bizarre reason the PO (or his mechanic) clipped off the old connector to the brown type sensor and replaced it with another gray type sensor and connector. I guess they must both be the same?

Any way, thanks for the help on this one. 203,000 miles and back on the road running strong, hopefully for another 100,000 miles. :D