2000 4.0 sohc coolant leak HELP

[grayskull]

I have a sohc motor that is losing coolant,but doesnt show on the ground.we changed the trans a while back.when the trans was out we noticed some coolant on the back of the motor on the drivers side. i put my hand over the top of the motor and put my fingers in what felt like a freeze plug.it was full of coolant.is this a freeze plug on the intake or just part of the intake.well now it is evidently leaking more now i put a whole galon in it and 2 weeks later had to put almost a whole gallon in it again.it is leaking down on the exhaust i think and burning off as we drive it. i can go into a curve to the right and instantly smell it burning..

 

[2000StreetRod]

No coolant in intake

There is no coolant connection to either the upper or lower intake manifolds.

I suggest that you check the thermostat housing near the front of the engine. It is made of plastic and can crack and leak. Then the coolant could be running to the rear along the top of the block. There are two sensors that screw into the thermostat housing. One of them could be leaking. Also check the hose that goes to the heater control valve.

The photo below shows the thermostat housing mounted on the engine with the upper and lower intake manifolds removed.

The photo below is of the thermostat housing after removal from the engine. The arrows indicate the sensors.

 

[rgonz26]

I have a sohc motor that is losing coolant,but doesnt show on the ground.we changed the trans a while back.when the trans was out we noticed some coolant on the back of the motor on the drivers side. i put my hand over the top of the motor and put my fingers in what felt like a freeze plug.it was full of coolant.is this a freeze plug on the intake or just part of the intake.well now it is evidently leaking more now i put a whole galon in it and 2 weeks later had to put almost a whole gallon in it again.it is leaking down on the exhaust i think and burning off as we drive it. i can go into a curve to the right and instantly smell it burning..

I also have coolant dripping from the bottom of the engine block (towards the rear) and onto the exhaust. I have checked the radiator, upper and lower hoses, and thermostat but do not see any signs of a leakage. I've read posts about the heater core and/or heater core valve leaking coolant but am not sure if a leak there would run down to towards the bottom of the block or how to check it for that matter. I am not sure where else to look for the problem.

BTW - I am new to this forum and would appreciate any help I can get. This site has helped me keep my vehicle maintained and saved me some $$$ along the way.

 

[ragajungle]

I have heard that some of the older 4.0L OHVs leak around the lower intake gasket, but I know you have a SOHC.


I just had to do the lower intake gasket on my 89 Bronco II - I was getting a weird leak too. Just a thought but it could be the lower intake gasket.

-Mike

 

[janolsson]

I have a sohc motor that is losing coolant,but doesnt show on the ground.we changed the trans a while back.when the trans was out we noticed some coolant on the back of the motor on the drivers side. i put my hand over the top of the motor and put my fingers in what felt like a freeze plug.it was full of coolant.is this a freeze plug on the intake or just part of the intake.well now it is evidently leaking more now i put a whole galon in it and 2 weeks later had to put almost a whole gallon in it again.it is leaking down on the exhaust i think and burning off as we drive it. i can go into a curve to the right and instantly smell it burning..

Below is a photo of the rear of the SOHC strppied down.
You can see that the left head has a flange that is identical to the one used for the thermostat housing on the right head. It's opening is sealed with a freeze plug.

Now you can also see the valley runs from front to back and so, as 2000StreetRod said it could be filling from the front and pouring out of the back. It could also be a rusted out freeze plug on the rear or it could be a hole somewhere in the head near the flange (i believe mcslug had this on one).
My advice would be pull off the intakes and have a good poke around. If you have access to a pressure kit this would help to pinpoint a leak if there is no obvious leak.
HTH

 

[grayskull]

so that was a freeze plug i put my finger in.i hope that is what it is and not the thermostat housing.Freeze plugs are alot cheaper.

thanks janolsson for the pics and to all for the help.

 

[rgonz26]

I have heard that some of the older 4.0L OHVs leak around the lower intake gasket, but I know you have a SOHC.


I just had to do the lower intake gasket on my 89 Bronco II - I was getting a weird leak too. Just a thought but it could be the lower intake gasket.

-Mike

Is it possible for coolant to leak from a bad intake manifold gasket on an SOHC? I thought it was just air and fuel circulating in there. How can I tell if it is the intake gasket and not the head gaskets (which I am praying it is not)?

 

[janolsson]

Is it possible for coolant to leak from a bad intake manifold gasket on an SOHC? I thought it was just air and fuel circulating in there. How can I tell if it is the intake gasket and not the head gaskets (which I am praying it is not)?

The photo above shows the SOHC without the intakes and you can clearly see there is no connection to the cooling system. A coolant loss to the outside of the engine more commonly would point to a hose, heater valve, thermostat housing or crack/hole in the head. Head gasket may cause this but much less likely.

 

[rgonz26]

The photo above shows the SOHC without the intakes and you can clearly see there is no connection to the cooling system. A coolant loss to the outside of the engine more commonly would point to a hose, heater valve, thermostat housing or crack/hole in the head. Head gasket may cause this but much less likely.

Thanks Janolsson. I guess I'll have to remove the intake anyway to get a better look and see if I can spot the leak.

 

[grayskull]

i kinda found the leak .down below the intake looks like another freeze plug just past the thermostat housing.looking at the motor from front to back.i watched it fill up with coolant. so its not the freeze plug in the back.it still could be the thermostat housing though.i guess i will have the take all that stuff off.aurgggg...

 

[Rockstarenergy]

i HAD a leak below my intake its a small hose u need to take your alternator off to get to it and its still a tight squeeze took me a while but i got it and i have no coolant leak anymore mine seems alot like yours check it out

 

[grayskull]

i HAD a leak below my intake its a small hose u need to take your alternator off to get to it and its still a tight squeeze took me a while but i got it and i have no coolant leak anymore mine seems alot like yours check it out

what motor do you have in yours?i have the sohc motor.its more likely to be the housing.because it didnt start leaking until it got up to temp.which tells me that the plastic housing swelled when it got hot at started leaking out of the crack.sure sounds logical.

 

[Rocketman1958]

GraySkull, I had the same loss of Coolant and used Redline "Water Wetter" Racing Coolant which has a florescent dye in it to help racers find the source and root cause of the cooling system leak, What I found was that the coolant was pooling on top of the engine in the bank between the valley or V of the heads near the thermostat housing and then would come back down the rear of the engine over time. Closer inspection with a black light revealed the thermostat housing was leaking after reaching operating temperature and seeping fluid out at the seams of the plastic housing. The 2001 XLS SOHC V6 2wd was purchased for my son and had 151K miles on it. My research as a former Ford Tech is that this failure of the thermostat housing is not uncommon, mine looks like the one StreetRod posted. My housing had one sensor screwed in and one held in by a retainer clip ( which was an update as some housings had both sensors screwed in), the sensor that was screwed in threads that were so corroded they were also leaking coolant under pressure. Signs of significant acidic corrosion on the brass interface for the brass bodied sensors into the housing, are evidence that the housing had been leaking for some time but the mold line of the upper and lower half of the plastic housing in the side was splitting and that was where most of the coolant was coming from and the plastic had swelled and distorted over all the miles. Not a great engineering decision of Ford to use plastic in a place of high heat cycling and a critical pressure point for the thermostat. My local Napa Auto parts store matched my old housing and I got new sensors, thermostat, thermostat gasket and used some 3M water pump gasket material to seal the sensors in. The housing is buried in there and if you take your time it not a bad DIY. I've been working on Fords for a very long time and there are things a like about them and some I don't. I will post some photos, once I read the protocol.