Hi guys,
I noticed a coolant leak the other day. I deduced that it was coming from the water pump. So I figured it was time to replace the water pump, thermostat, and all gaskets.


After a half of a day fiddling around, cleaning around the engine, changing oil, installing the dipstick tube adapter fix, I was feeling good. my truck got it's much needed TLC.


It was now time to pour the oil and coolant back in. I still have the same coolant leak as before. It's hard to see without removing the ac compressor but it looks to be coming off of the block (possibly head) behind the thermostat housing and maybe an inch below.


What is in that are that could be causing the leak? Is there a plug in the head with a bad o-ring? I find it hard to believe that it would be a head gasket or a cracked head/block.


Thanks for the help guys.

 

Had you already ruled out the thermostat housing itself as the leak source, before replacing the water pump? Did you try backing up the thermostat housing flange with a reinforcement ring like this? - https://www.strictlydiesel.com/p-267...sing-ring.aspx

It might be leaking from one of the temp sensors.

 

The temp sensor in the WP was dry, as well as the pipe plug below the thermostat.
And the thermostat housing was dry all around the flange also.

 

bump, anyone have any ideas?

 

I have always had to thin skim the o ring and the bottom of the thermostat housing to keep them from leaking, probably not your problem being you housing is dry, but here's a bump to the top.

 

Is there any chance the coolant hose is cracked? Maybe under the hose clamp? Other than head, I'm drawing up a blank as to what has coolant circulating through it with the engine running. Are you positive it's coolant leaking?

If it were fuel, the orifice bolt (?) on the front of the left head might be leaking.

 

The hose and clamp are good. I am 100% that it is coolant. It drips without the engine running at a decent rate and it slows then the engine is running.


I am going to pressure test it tomorrow to try to verify the leak location. It looks like I need to remove the AC compressor to get a better look.


My truck is kept at my parent's house 40 miles from my house so it is hard to get over there to work on it during the week.


Thanks again for the help boys.

 

Sounds like the same problem I was having. I am trying to let a few people know about the aftermarket gasket leaks. I posted this to help a couple people. I am thinking Riffraff is selling the proper Motorcraft thermostat too.

I have found a lot of people are having problems with the thermostat housing is leaking on the 7.3s. The problem is the aftermarket people, zone, adv, oreilys, napa all sell an O ring to seal the thermostat. It will seal for a while, weeks months ??? You need to go to Ford and get a OEM thermostat. It comes with a seal on it. It covers both sides of the thermostat. It is the only one that seals correctly.

BTW the therm set me back almost $40 but it did not leak. Much better seal than the little o ring.

 

The billet thermostat cover will fit, you just have to change the radiator hose. Here are some links to the proper Motorcraft thermostats as well.

Motorcraft Thermostat 94-95 - Riffraff Diesel Performance

Motorcraft Thermostat 96-03 - Riffraff Diesel Performance

Riffraff Diesel 7.3L Billet Thermostat Housing

 

I hope I am wrong but after I chased and chased my leak, it was leaking on each side of the front oil cooler flange. It appeared that someone overtightened the oil cooler bolts and cracked the bolt hole. You can hang the AC compressor from the hood and remove the air pump without removing any pulleys. Then suck the power steering fluid out, disconnect the lines (plugging the bottom one with a hose and bolt), and the power steering pump will come off with the bracket. You can then get a better look at the backside of the flange with a mirror. If you are really careful you can remove the serpentine belt and start it but I could see mine dripping without it running. I hope that is not the issue but my motor is on the ground for the exact same thing.

 

The timing cover is probably leaking. They get rotted out. That's what happened to mine.