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Unknown Coolant leak.

Aussie Explorer

Well-Known Member
June 3, 2005
Reaction score
City, State
Western Australia
Year, Model & Trim Level
98 XLT
I have lost 2 litres of Coolant in around 2000K, but can’t find the source of it, The majority of the dried coolant seems to be concentrated around the left exhaust manifold between the front 2 ports with hardly anything on the very back port. It has also made it’s way onto the side of the block and over the heater hoses coming out of the water pump too.

There is also a bit down near the crank pulley.

All the hoses are new and don’t have any real trace of coolant leakage from them and there is no oil in the water or water in the oil.

So I am looking at Water pump Gasket as the culprit t< But why the concentration of coolant would then be around the Left exhaust manifold I can’t explain.

The only other thing I can think of is maybe the left bank head Gasket but the spray pattern of the dried coolant around the engine doesn’t look rite for that.

I have hosed it all off and am going to look at the engine after each drive to try and pin point the source.

If any of you guys have any ideas or input of what it might be post it up all help will be appreciated.

It’s a 97XLT V6 SOHC with 152,000K’s on it.

I am prying it’s not a head gasket as I am getting ready to sell it in a month or 2 and having to change a head gasket on a SOHC engine rite before I sell it would make me real unhappy. LOL

Thanks for any help.

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Last edited:

Try using a cooling system pressure tester to pressurize the system. You will see where the leak is coming from when you pump it up.

BrooklynBay said:
Try using a cooling system pressure tester

Care to elaborate? I have an annoying small leak somewhere that I have never found. :confused:

What is it? Where do I get one? and How much would it cost?

I have also heard of using dye in the system. Again...no idea where to get such a thing.

EDIT: :D You posted while I was typing. Now at least I know what to look for.

Aussie Explorer said:
It’s a 97XLT V6 SOHC with 152,000K’s on it.

Same motor, similar leak. Most of my coolant is coming down the front of the motor, around the water pump and down the oil pan. I've been trying to find the source, but can't see much without taking anything apart.

So, today I got a new water pump and started taking everything apart. By the time I got to the water pump, I wasn't convinced it was the water pump anymore. It appeared to be coming from the black thermostat housing assembly, on the bottom right front (driver seat reference).

Once I realized I couldn't get the thermostat housing out without taking out the intake manifold, I gave up and just replaced the water pump. I am so disappointed in myself for not finding the real cause, but I didn't have the time, tools or patience to take all that crap off of the top of the motor to get to the god damn thermostat housing. I'm starting to hate ford LOL.

Anyway, I think I'm going to take it to a mechanic to let him curse at the car for me. Let me know if you find the source of your leak, I may want to take a deep breath and try again.

Check the 2 links in post # 4 for more information. I purchased my tool from WWW.Eppys.Com. AutoZone might have a loaner for you to borrow.

I replaced the thermostat in my '01 in around 10 minutes. It has the 4.0 SOHC. Is your different?

I think I found something, looking down into the Valley I can see a fair amount of what looks to be coolant, am going to have a closer look with a flash light but it look’s as if the intake manifold will be coming of this weekend for a closer look at the back of Theostat housing.

If it’s the F**king O ring in the Theostat housing agene I will be Pissed the F**king thing has been replaced 3 times buy Ford back when it was a lease car, well I will find out in a few days when I pull it all down.

My coolant pools in the front on the passenger side also. I haven't figured out were its coming from yet. I check two AutoZones for pressure testers, but both of them didn't have the correct adapter to connect to the radiator. Strangly it had an adapter to check the cap, but not a reducer to the smaller radiator openning.

AutoZones around me don't have dye either. Off to Napa....

Aussie Explorer said:
.... O ring in the Theostat housing agene I will be Pissed the F**king thing has been replaced 3 times buy Ford back when it was a lease car, well I will find out in a few days when I pull it all down.

Is the O ring that goes around the thermostat the only gasket for that housing? When I bought my gasket kits it also came with a fiber gasket, but I didn't put it on, because it wasn't there when I removed the thermostat.

Don't use sealant with a rubber O ring. It will cause leaks.

Brian_B said:
I replaced the thermostat in my '01 in around 10 minutes. It has the 4.0 SOHC. Is your different?

I was talking about the whole black plastic housing that houses the thermostat. It has all the sensors connected to it. I believe the leak is coming from where this housing meets the top of the motor - lower intake manifold?

You are correct, the thermostat itself is a quick job.

This leak is not making it self easy to diagnose, it looks as if it could be the Water pump gasket perhaps, I am going to have to wait till the weekend so I can pull some stuff of the engine for a better look.

I had the same problem with my 98. There is a small hose behind the thermostat that goes to the heater core. It plugs in to the plastic thermostat housing. If this hose leaks you will not see it unless you start taking parts off the front of the engine. It is right under the throttle body. I had to take the throttle body off to see mine. My hose was not leaking though , the plastic neck for the heater hose to hook to was cracked.

Same with my 98XP.. I'm lossing coolant only in the reservoir..but radiator seems OK no leak under..But I don't want to take risk of not filling the reservoir again and again

Check the radiator cap.