Mysterious coolant leak.....

[Wyoguy222]

Alright guys, I have been losing about 1 gallon of coolant a month, very slow leak. I am now losing about a gallon a week.....I have looked everywhere, changed a few hoses. One thing I noticed is that coolant seems to be pooling ON TOP of the engine. Here is a couple pics.....where the heck could it be coming from?? Any ideas?

 

[Mr. Alligator]

Mysterious thermostat housing?

 

[FF_RSQExplorer]

Common plastic tstat housing or cylinder head gasket or head.

 

[koda2000]

Common plastic tstat housing or cylinder head gasket or head.

FYI, The OP's pic appears to be a 4.0L OHV engine, so no plastic t-stat housing.

 

[swshawaii]

^ Ditto koda. Pretty easy to ID the OHV looking at the "strange" 90* intake tube. OP, save yourself time and aggravation and "borrow" a
coolant system pressure test kit loaned from most auto parts stores with a 100% refundable deposit upon return. Call around for availabilty.

Or use coolant dye and a black light in the dark.

 

[lobo411]

The water outlet is steel on the OHV, and it tends to corrode/pit. Try replacing the upper radiator hose. You may also have to replace the clamp with a worm-drive clamp. Mine won't seal unless I tighten it to the point of distorting the clamp (using a ratchet).

If I don't tighten mine that tight, then coolant will leak past the clamp and pool on top of the lower intake manifold...except it won't always do it. Usually, it only leaks at a specific time, such as 5 mins after engine shutdown. So it could be leaking for a long time without you noticing, because you're looking at the wrong time.

 

[Wyoguy222]

Thank you for all the responses! I will definitely borrow a pressure tester, and see if I can find the leak. I just replaced the upper hose but maybe the clamp isnt sufficient. Gonna tear into this, this coming week

 

[Wyoguy222]

Oh and yes OHV. ITS A 1995 Ford Explorer Expedition.

 

[Turdle]

You do need a new water neck ( thermostat housing) for sure. It may have a pinhole leak at high temp and revs. There are 2 sizes used, so you need to get the correct one. Even if this is not the source of the present leak, I can say for sure it will be the source of the next one.


DORMAN 9021012 is 40 mm diameter neck

DORMAN 9021007 is for 35mm diameter neck.

I think 95 up ( 95tm) use the smaller one but I might be wrong. The part number is stamped around the mating surface ring, and will start with either 90 tm or 95 tm from what I recall.

I got the above numbers from the rockauto dot com website, under 1995 ford explorer cooling system thermostat housing.

Also make sure you got the right size hose.

Another thing to check, , the heater hoses could be leaking under pressure. sometimes it helps to have someone rev the engine with a full cooling system. If there is a pinhole leak the engine revs will make it spray out more, which might make it easier to spot.

 

[wcjeep]

Those manufacturer clamps can be a pain. However, they are designed to exert even force at all points on the hose. Is your clamp in the proper position? I can't tell from the pic if it's touching the inner bump of the steel neck.

 

[koda2000]

Those manufacturer clamps can be a pain. However, they are designed to exert even force at all points on the hose. Is your clamp in the proper position? I can't tell from the pic if it's touching the inner bump of the steel neck.

Tip: If you're reusing a hose it's important to reinstall the clamp, regardless of type, in exactly the same position as it was in when removed to prevent causing a leak.

 

[Wyoguy222]

It is the housing. So how do I know if I need the 35mm or 40mm thermostat housing? Where do I measure?

 

[Bootless]

just do what i did when i put mine back together i used rtv on the inside of the hose and have had no more leaks

 

[Nate Tidwell]

Cheap or failing water pumps tend to leak out the weep hole. Took me a while to find the leak on my 5.0, found it accidentally while turning the crank to get tdc to replace my cam synchronizer.