Slight coolant leak

rgorke

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‘04 V8 with the entire coolant system replaced in the past 3-5 years with Motorcraft. While driving, the temp stays <205 and <200 on the freeway.

I had to pick my sister up at the airport a week or so ago and the temp went up to 225 sitting in traffic. Once moving again the temp dropped quickly.

I found some tell tale signs of a leak behind the crossover pipe and down towards the 9N499 pipe (see pictures).

I am pretty certain the plastic parts are good but based on the pictures, could the O rings and/or gaskets go bad?

That or possibly the water pump leaking? It was replaced 5 years ago but not Motorcraft.

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Yep, I had a very difficult to resolve leak in that area on my 04, with new plastic. I thought it was the big o-ring, but managed to determine that it was not after replacing it a few times. (I finally wrapped some plastic around different parts to verify where the leak was. One of the o-rings between the cross over and one of the heads was not completely sealing to the head, I polished the mating surface and put some tackseal on the o-ring and ended the problem. I would not have thought that a leak there would spray up on to the top of the engine. I could not get it to leak while stationary with a max engine RPM of 2500. Apparently, it had to be closer to 6000 to cause it.
 
Yep, I had a very difficult to resolve leak in that area on my 04, with new plastic. I thought it was the big o-ring, but managed to determine that it was not after replacing it a few times. (I finally wrapped some plastic around different parts to verify where the leak was. One of the o-rings between the cross over and one of the heads was not completely sealing to the head, I polished the mating surface and put some tackseal on the o-ring and ended the problem. I would not have thought that a leak there would spray up on to the top of the engine. I could not get it to leak while stationary with a max engine RPM of 2500. Apparently, it had to be closer to 6000 to cause it.
Thanks…that helps a lot. I have replaced the 9N499 O ring where it connects to the block a couple of times. So there is a history there.

Was it the passenger side? Seems like a leak there could drip onto the belt and get flung up underneath.

I just went out and took another close look and could see coolant stain on the front cover between the water pump and the balancer.
 
IIRC... the o ring on the driver's side of the crossover leaked at one point on my V8. Makes me think that the crossover needs to be tightened down in an "X" pattern. Just a hypothesis.

Sounds like maybe your water pump seal is going bad too.

And yes... it seems the weakest point of the cooling system is the 9n499 gooseneck and O ring.

I have replaced that O-ring more than once... between cooling system rebuilds.

I've half thought about epoxying the gooseneck and crossover together with JB Weld, and see what happens.

The only reason I think the engineers made those parts 2 pieces, is because of thermal expansion in 2 directions.
 
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IIRC... the o ring on the driver's side of the crossover leaked at one point on my V8. Makes me think that the crossover needs to be tightened down in an "X" pattern. Just a hypothesis.

Sounds like maybe your water pump seal is going bad too.

And yes... it seems the weakest point of the cooling system is the 9n499 gooseneck and O ring.

I have replaced that O-ring more than once... between cooling system rebuilds.

I've half thought about epoxying the gooseneck and crossover together with JB Weld, and see what happens.

The only reason I think the engineers made those parts 2 pieces, is because of thermal expansion in 2 directions.
Exactly...I have replaced the 9N499/block O ring twice! My initial thinking is to replace all of the O-rings/ seals in the cross over and 9N499 and put in one of the Jag water pumps with the metal impellers.

In terms of O-rings, there are 5:
(taken from GenII LS8 Cooling System Overhaul)

* "HR1" / "707299-S300" (*top* O-ring for the 9N499 to 8548A)
* "8255B" / "4Z-8255-CA" (*bottom* O-ring for the 9N499 to engine block)
* "8255A" / "JV-8255-CB" (The 2 O-rings from 8548A to front face of engine block)
* "8590" / "9Z-8590-AB" (Large O-ring from 8548A to 8592)

Of course, Rockauto does not have all the OEM part numbers for the O-rings, specifically the ones in the "kits". What I am having difficulty finding is the "HR1" O-Ring. It is different than the other seals that are flat, it is a true O-Ring. Ford Parts giant purports to have the HR1 but in a four pack...

Anyone have an extra HR1 or at least the specs...diameter (53mm?) and thickness?
 
I believe that it is M5x52. This is based on research I did 11 years ago, so I can't vouch for it anymore. The other important thing is the material. I guessed at Nitrile, but I can't stand by that either. I never did a long term trial.
 
I have replaced the gooseneck O-ring a few times. Seems the best way to make it not leak for a while, is to lube the O-ring with some coolant and "work it in" from the back... then torque the bolts. All without messing with the crossover pipe.

If you notice, the O-ring starts out as round... but when it starts leaking the O-ring is almost flat.

Gotta be why the O-ring comes in a 4 pack.
 
All back together and only took two rounds of bleeding with the nose down…

Pretty sure the culprit was the 9N499 to crossover O ring. What came to mind was a play on a Queen song…Flat Bottom Girl.

I did clean and polish the crossover to block connections.

Temp is staying under 200 on the road. Of course it’s on 59 degrees…but I’ll take it.

Next project is taking off and cleaning the belt. I spilled coolant all over it and it squeals like a stick pig.

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Yep, I had a very difficult to resolve leak in that area on my 04, with new plastic. I thought it was the big o-ring, but managed to determine that it was not after replacing it a few times. (I finally wrapped some plastic around different parts to verify where the leak was. One of the o-rings between the cross over and one of the heads was not completely sealing to the head, I polished the mating surface and put some tackseal on the o-ring and ended the problem. I would not have thought that a leak there would spray up on to the top of the engine. I could not get it to leak while stationary with a max engine RPM of 2500. Apparently, it had to be closer to 6000 to cause it.
Good info. We will try that trick when we chased the coolant leak issue in the 04 project.
 
Thanks for the link to the improved WP with the metal impeller!
Nice addition to the 3.9L Lincoln LS engine for sure!
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Well, I’m back at this…driving around town and even a long trip - 100 miles each way - everything is great. Yesterday, I have do a one day round trip up to Sacramento. Driving home from LAX on the 405 is a nightmare…sitting in bumper to bumper traffic. All of a sudden the ETC fail safe light goes on and I head over to the shoulder.

I plugged in my OBD2 reader and see the coolant temp is 225 and two pending codes P2106 and P2135. These are related to the throttle Actuator and Throttle/Pedal position voltage correlation.

I turn off the car and sit there for several minutes trying to determine what to do. I started the car back up and the ETC code went away and I cranked the defrost to get the temp down. No other issues the remaining 40 miles home.

I will investigate the throttle/pedal issue but the white stain is back on the underside of the 9N499 neck. A water pump and gasket are on their way since there isn’t anything else under there that I haven’t replaced in the past year.

One hypothesis is that the coolant may have sprayed onto the throttle electrical connection and caused the ETC issue. Unless the P2135 code is sole related to the gas pedal.
 
ETC failsafe has nothing to do with engine temperature at all, and 225 is a reasonable temperature in traffic and is not overheating. You can usually lower the temperature by turning the AC on (makes the fan run faster).
My 04 would randomly throw the ETC failsafe with those codes when it got older. I tried reseating connectors and such with no changes. Finally, I swapped the throttle bodies between my 06 and my 04. I expected that the 06 would have problems then, and I would know to order another throttle body. Instead, neither car had ETC failsafe, so I just left it that way.
 
ETC failsafe has nothing to do with engine temperature at all, and 225 is a reasonable temperature in traffic and is not overheating.

Currently with a bad coolant leak im running about 212 highest 215 and the fan is roaring away. With no leaks i was always around 196-200.

Its also always this O-Ring that leaks due to a loose fit. The Jaguar uses a yellow plastic clip to hold these two parts together. Not sure why the LS never came with this..
 
Look man. There is a rubber hose that runs from throttle body under manifold that leaks. It may or may not be available but you can make something up and if you are good you can do it without removing manifold. Try a slightly bigger viton o-ring at the 53mm thermostat housing. Also, if the connector locks are broken on any throttle body plug fix it or you will always have ETC issues. The EGR valve goes bad too.
 

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