problem with cooling system.

[1991fordexploder]

I am loosing coolant somehow. i dont see any leaks nothing on the ground.
and today i was leaving work and was driving while the engine was cold, ( i know bad idea, im a mechanic i should know better.) and the temp needle jumped to the end of normal and then went back down. so i pulled over to check the coolant and its was low, while filling the radiator i saw alot of foam or frothy coolant. what does this mean when you have frothy coolant. thanks for your help.

 

[dogfriend]

what does this mean when you have frothy coolant. thanks for your help.

Unfortunately, it usually means that oil is getting into the coolant. You should also check for the presence of coolant in the oil (milky color to the oil) which is even worse because oil with coolant doesn't lubricate as well as regular oil.

The reason that oil is getting into the coolant is probably either a) blown head gasket and/or b) a cracked head or block.

 

[swetrid]

Probably cracked cylinder head or blown head gasket. Very common on 4.0l OHV engines.

 

[1991fordexploder]

That's what I was afraid of. So its not possible that the water pump could've just churned the coolant and made it frothy because it was low?

 

[dogfriend]

Performing a compression test can tell you if you have a blown head gasket or cracked head.

 

[1991fordexploder]

It was low on coolant again this morning. And again nothing but bubbles. There's no coolant in the oil. Don't these engines have problems with freeze plugs?

 

[dogfriend]

If it is a freeze plug (or other leak) you should see the residue from where the coolant is leaking out and/or drips on the ground. If you are losing coolant but no residue from dried up coolant on the leaking parts and/or drips on the ground, it means that the coolant is disappearing out the tailpipe, i.e. head gasket or cracked block.

 

[kevinsranger]

It was low on coolant again this morning. And again nothing but bubbles. There's no coolant in the oil. Don't these engines have problems with freeze plugs?

If it is a freeze plug (or other leak) you should see the residue from where the coolant is leaking out and/or drips on the ground. If you are losing coolant but no residue from dried up coolant on the leaking parts and/or drips on the ground, it means that the coolant is disappearing out the tailpipe, i.e. head gasket or cracked block.

my 94 has bad freeze plugs, they are rotted out from age, there is no coolant leaks where i park the truck, it drips out and burns off against the engine block. if i go under the truck then i can see some wet antifreeze that never burned, but like i said there is no evidence of coolant on the ground where i park, so keep an eye on them

if you have a body lift (i do) you can see the freeze plugs between the gap while the engine is running and watch the plugs "sweat" coolant

 

[ahodges]

I don't know about any problems with the freeze plugs but that year has both head gasket problems and a problem with getting small cracks in the heads.. I would have to guess you at least have a head gasket problem..

 

[1991fordexploder]

Y'all know what this means, time for a 5.0 swap!

 

[ahodges]

Y'all know what this means, time for a 5.0 swap!

 

[1991fordexploder]

ok so i put some uv dye in the antifreeze and cannot find a leak. as far as i can tell the freeze plugs are dry and there is no coolant in the oil or oil in the coolant. so how do i find out if it is being burnt without removing the heads? this is my daily driver.

 

[dogfriend]

so how do i find out if it is being burnt without removing the heads?

Compression test or cylinder leakdown test.

 

[wood1]

My '91 had the same problem. Rather than pulling the top end I first wanted to try some more simple cures. I found that my lower intake manifold bolts needed to be retorqued. That and a bottle of Barr's Stop Leak every 6-12 months has kept my beast going. I still use a little coolant but not even close to what it was. Yeah yeah, there are lots of you guys that don't like Barr's, all I can say is that it seems to work in this situation for me. I'm guessing mind you, but I think that once I do rebuild I will find a bad head gasket or cracked head in addition to the bad lower intake manifold gaskets. A nice bonus from tightening the lower intake was that oil consumption went from about a liter (IIRC) every 2 weeks, down to what one would normally expect for a 300,000+ km engine.