4.6L coolant leak, rear of engine

[A1cntrler]

Since I replaced my radiator a year ago in the Trac (seeping tank ends) I have made it a habit to keep an eye on the coolant level weekly. It has lost some and I top it off but have never seen any seepage or dripping anywhere to indicate where the leak may be coming from. It has never been a major leak, as I add maybe a couple cups of coolant every couple months.



The other day as I was backing out of the driveway after letting it warm up for about 10 minutes I saw a spot on the driveway. I figured it was just the dew that I wiped off the windshield. When I returned home a couple hours later the spot was still there. Did the finger test and sniff, and it was the sweet smell of antifreeze. I put the Trac up on stands and didn't see anything on the underside to indicate where it had come from. Up top I did see a hose coming off the control valve in the heater lines with residue running down the metal part of the line from where the hose is clamped to it. I've ordered a new hose and a couple of clamps to replace it, but that spot although it has the white residue, has always been dry when I swipe my fingers under it.



Today I let it warm up like usual and looked under it before I backed out and saw it dripping off the rear engine crossmember on the driver side. I drove my son the 2 miles to school, returned home and put it in the air again and went under looking for the source. It was dry by then and no sign of a leak existed except for a couple drops still on the crossmember. I fired the trac up while it was on the jackstands and let it idle for a bit hoping to see where it was coming from. Nothing to be seen. I could see a dried trail coming down the bellhousing on the drivers side, but still couldn't see where it originated from.



It seems to only exist on a cold start. Now if it is still happening, but it is getting burned off on something prior to making it all the way down, I don't know. I don't smell any burning off, so I don't think it still is. Is it possible that once the engine heats up wherever the leak is coming from is sealed off from expansion? What is under the intake manifold there that might be leaking/seeping coolant out?



It is parked on a slight hill in my driveway overnight, so it is possible it could be coming from the front, but I checked the usual culprits (t-stat housing, hose clamps, water pump seep hole) and all are dry even while it is dripping before I have to leave.



Hopefully on Sunday I'll get it in the garage when it is cold, up on stands and running so that I can hopefully pinpoint the source. It s supposed to rain here tomorrow, so even if I got it up in the air everything will be wet anyways but Sunday looks ok weatherwise so far...

 

[A1cntrler]

I shoved my phone up in there and snapped a couple of pics just to see what might come out. The silly front differential is right smack in the way of a clear view, but anyways here are the two that came out.



The first one here shows where it ends up dripping from:







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This one shows where it drips onto the cross member from:



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And this was the blind shot I took with my hand up on top of the differential. Still doesn't tell me much:



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[Gavin Allan]

Put some Barr's leaks in it and be done with it. Auto assembly plants routinely put a small amount of stop leak in the cooling system when new to prevent small leaks like this.



I used to work in a plastic molding manufacturing. We heated aluminum molds by circulating auto antifreeze through them. Many of the molds would leak small amounts when cold, but they did not leak a bit while they were warm 24/7, However, during a plant shutdown and they cooled off, there were little puddles everywhere!



I'm just thinking practically here. For sure, if you can fix it, that would be the better way to go. However, it may be one of those things that is too difficult, expensive, or impossible to fix. I am not afraid of stop leak since I have been made aware that some manufacturers use it prophilactically in their new cars.

 

[A1cntrler]

I don't really want to put a bandaid on it. I still have 8k miles left on my Mechanical breakdown insurance, and would rather get it fixed right. That being said I don't want to take it in to pay my deductible if it is something as simple as a leaky hose/clamp I can't see back there. Was just wondering if someone else has had this happen yet and if so, what/where is the culprit?

 

[A1cntrler]

some manufacturers use it prophilactically in their new cars

That's a word that when I woke up this morning, thought I would like to use in a sentence today. lol



Yeah I used the old googles to see what the general word is on using them. Having worked in an auto parts store before, we sold the stuff, but the mechanics that came through buying stuff told me to shy away from products like that because they usually cause more problems than good over the long run. Not planning on getting rid of my Trac, so I would like to just keep it working as intended, however I also did see where manufacturers have been putting it in at manufacture to prevent (prophilactically :banana drips/leaks and I'm sure cut back on warranty visits for that drip in the garage.

 

[scott degroot]

Alot of times I see the coolant crossover manifold (what the thermostat sits in) start to leak at the gasket where it connects to the cylinder head. This lets coolant either get in the valley under the intake manifold or collect on the edge of the head where the intake manifold meets the cylinder head. The coolant then runs to the back of the engine and leaks down the backside like you are seeing.

 

[A1cntrler]

Alot of times I see the coolant crossover manifold (what the thermostat sits in) start to leak at the gasket where it connects to the cylinder head. This lets coolant either get in the valley under the intake manifold or collect on the edge of the head where the intake manifold meets the cylinder head. The coolant then runs to the back of the engine and leaks down the backside like you are seeing.

So it could still be coming from the front of the motor.. I couldn't see back there to look for the wet spot. I've ordered a mechanics mirror off Amazon so that maybe I can sneak a peek into places I couldn't see before. If it is the crossover manifold like you say, it is a o-ring type gasket or a paper one? Either way the intake manifold has to come off to access it, but doesn't look like too bad of a job for me to do on my own. Thanks L1.

 

[A1cntrler]

Is this the location of the leak you're talking about L1? I know it is the incorrect intake but it is of similar design. Not where the aluminum meets the plastic, but where the plastic pops into the head, right?







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[A1cntrler]

I assume the 4 gaskets along the top here are for the crossover pipe, am I correct? 2 for the head connection, and two for the plastic to aluminum connection?



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[scott degroot]

That's it. Shoul be a pretty easy leak to locate if that's where it's leaking from. If you can't see it leaking then get the cooling system pressure tested, however make sure that the truck has sat overnight so the engine is cold or chances are you won't find the leak being that it seals itself once the engine starts to warm up.

 

[A1cntrler]

That's the spot. Saw it this morning and could see the trail of wet along a little channel along the head there(almost as if the channel was designed there to divert the flow from going into the spark plugs). Now I'll just wait until my Service Manual I ordered arrives this week to see if I want to tackle the job myself. Really it doesn't look like it will be that difficult to remove the intake. Just a little time consuming...

 

[scott degroot]

Glad you found the leak. when you get it apart look at the area where the coolant manifold connects to the head and make sure that the cylinder head isn't starting to get eaten away where the seal rides. If it is don't worry, clean the area really good and pick all of the loose stuff that you can out of the pitted away area, mix up some JB weld, fill in the pitted area, level it with razor blade scraped across the surface of the head and then let it sit up overnight before reassembly. I've done a bunch of them this way and have never had an issue...sure beats replacing the entire cylinder head

 

[A1cntrler]

I ordered the FelPro gasket set for the intake pictured above. Should be here in a couple days. Might tackle it this weekend. It seems that for now since the cold snap has passed, the leak has stopped. I'm sure it is only temporary though, since these things don't heal themselves.. I guess temps in the low 30's at night instead of the 50's can make a difference.

 

[scott degroot]

I've done 3 of these on 5.4 Expeditions in the last 2 days, unfortunately they all needed new intakes due to the coolant destroying the manifold.

 

[A1cntrler]

I've done 3 of these on 5.4 Expeditions in the last 2 days, unfortunately they all needed new intakes due to the coolant destroying the manifold.

Are those the ones that have the Aluminum crossover, but with plastic sandwiched between that and the head?



Mine is a separate crossover (I tell you this, but you already know lol)



Unrealated, but just want to pick your brain real quick :1996 Explorer, heater control valve. My brother has to replace it every couple months because they keep leaking. Finally just told him to go get a Motorcraft one, but is there an upgraded one with better internals that won't spring a leak? My '01 Trac I had to replace it several times, and my '07 Trac has had it replaced once so far for leaking...

 

[scott degroot]

You are correct on the Expedition intakes where the intake gets eaten away. Ford realized they goofed and redesigned it to what you have now but the probelm is those ones eat the cylinder head away.



As far as the heater control valves go...they all suck. I've had some luck installing a flow restrictor in the supply hose to the heater control valve.

 

[A1cntrler]

Oh yeah..forgot to report back. All went well on the surgery here. It was more time consuming than difficult. Went ahead and did the Fuel Filter too while I had the fuel system depressurized (shocked to find I didn't need any tools to break the fuel filter free... I expected it to be the typical spring type locking fuel line).



After I got it all apart I discovered that it was actual leaking on the backside of the thermostat housing, but since I already had the intake off and the new gaskets i hand I went ahead a popped them on there. No leaks!



I ran a bead of RTV around the thermostat housing there and placed it straight down onto the housing (removed the rear bolt that you can slide the "notched" housing onto) ti keep the RTV from sliding off. Torqued it down, wiped the little that oozed out and it too has been dry. If I've ever got to do it again I'll get the set of injector O-rings too. Just because I don't like putting dirty looking stuff back in there, and they were dirty/grimy but cleaned up ok.



Thanks for the help/tips! :haveabeer: