Blown Head Gasket? Air In The System?

[BuckSatan]

A few days ago I took the temperature sending unit off and went to buy a new one. Since I let it sit, I allowed air get into the system. Not realizing, I started the car and coolant poured out out the overflow. I then ran the car with the cap off and the front end jacked up... the expected bubbles came out.

Since then my temperature gauge will go just a little bit above the halfway mark then drop to a little before the halfway mark the first time. Subsequent times it goes to the halfway mark then drops down a little bit (not even a full mark). It will continuously do this as the thermostat opens - I assume. Also related I am sure, the radiator cap is not getting hot.

Lastly, I've now had to refill the overflow tank twice after driving it for a bit - probably 8 ounces both times. I do not have to fill it every time I drive the car. How can I tell if this is due to the system burping while being driven or I have blown a head gasket due to the air I let into the system?

 

[BuckSatan]

Even though the radiator cap doesn't get hot/warm.. I was able to confirm it is holding pressure. Messy, but worth some peace of mind.

I pulled a few spark plugs, and they looked new.. So, that seems to be a good sign..

 

[mikestang63]

Ok. the temp sending unit is is higher than the radiator, so it shouldn't be letting air into the system. I don't see how letting a car sit lets air into the system. Actually, you can remove the temp sending unit and fill up the system from the hole in the manifold until the coolant is just below the sending unit and you will know no air is in the system.

Regardless, if you have air in the system, keep filling up the overflow for a few days and eventually the air will work out normally. If you want to address it sooner, spend $30 and get a Lisle funnel and fill the system using that, It will clear out all the air in the system without having to jack the car up. Make sure the heat is on all the way to warm and the blower motor on high.

 

[BuckSatan]

Hmm.. Then I can't figure out how air got in. The only other thing I did was replace the ACT sensor. It's what I meant to replace, when I puled the temp sending unit - oops. Could the ACT sensor cause any of this?

 

[mikestang63]

Both the ACT or Temp sending unit are higher than the radiator neck. Just do per my earlier post and you'll be fine.

Why were you replacing the temp sending unit in the first place and did you put some teflon tape or past on the new sending unit upon install.

 

[BuckSatan]

Both the ACT or Temp sending unit are higher than the radiator neck. Just do per my earlier post and you'll be fine.

Why were you replacing the temp sending unit in the first place and did you put some teflon tape or past on the new sending unit upon install.

Yeah, I'll do that tomorrow.

I pulled out the temp sending unit by mistake.. I put it back in once I realized my mistake and reused the original teflon tape...

I was meaning to replace the ACT sensor - it was the original unit and my mechanic thought it might have something to do with some issues I have been having. I did put new teflon tape on that.

 

[mikestang63]

Yeah, I'll do that tomorrow.

I pulled out the temp sending unit by mistake.. I put it back in once I realized my mistake and reused the original teflon tape...

I was meaning to replace the ACT sensor - it was the original unit and my mechanic thought it might have something to do with some issues I have been having. I did put new teflon tape on that.

"reused the original teflon tape"?

That's not smart. It's like $.69 for a roll. Is it worth the risk of leaking or having it break off and ruining your sending unit by reusing 25 year old tape.

What issues are you running that your mechanic said to replace the ACT sensor? Did anyone run the codes or are you throwing parts at it?

 

[BuckSatan]

"reused the original teflon tape"?

That's not smart. It's like $.69 for a roll. Is it worth the risk of leaking or having it break off and ruining your sending unit by reusing 25 year old tape.

What issues are you running that your mechanic said to replace the ACT sensor? Did anyone run the codes or are you throwing parts at it?

You have a good point and I will replace when I take it off tomorrow - but it's not particularly old tape. The only codes I have are 44 and 94, which was thermactor and air pump. I am getting some gas in my oil. He thought it was probably the fuel pressure regulator but said it would be a good idea to replace the ACT too.

I could do the ACT without removing the upper intake, so I did that. I can't get the FPR without removing the upper - and I don't trust myself to remove it so I'll have to bring it in for that.

Next bet would be a stuck injector.. which again, I don't trust myself to handle.

 

[mikestang63]

You have a good point and I will replace when I take it off tomorrow - but it's not particularly old tape. The only codes I have are 44 and 94, which was thermactor and air pump. I am getting some gas in my oil. He thought it was probably the fuel pressure regulator but said it would be a good idea to replace the ACT too.

I could do the ACT without removing the upper intake, so I did that. I can't get the FPR without removing the upper - and I don't trust myself to remove it so I'll have to bring it in for that.

Next bet would be a stuck injector.. which again, I don't trust myself to handle.

pull the vacuum line off the FPR and smell it- if it smells like gas then the diaphragm inside is most likely broken, You can also hook up a hose and a vacuum gauge or just suck on the hose and put your thumb over the hose and see if it holds vacuum- you should feel it pulling on your thumb. You can remove it with the upper on but you have to use an allen wrench to get the bolts as they go in from the bottom.

Not trying to be rude, but if you plan on owning a fox body, you really should get used to working on them as they are 25+ years old and are not very difficult to work on, Get a chiltons or spend $15 and subscribe to alldata- online repair manuals.

There are many guys here that are very helpful and will gladly lend a hand to help you diagnose what's wrong. Code 44 and 94 could be the smog pump, blocked crossover tube at the back of the heads, cracked vacuum lines. If you removed your cat pipe, then no need for the smog pump and disregard the codes.

Easy way to check injectors- take a long wooden handle or screwdriver and place the tip on the injector and the other to your ear. You should hear it clicking on and off. Dump a can of Techron in a full tank of gas and that may free up a sticky injector. Another way is pull out an injector one at a time, crank the car with the coil wire grounded and hold the imjector over a cup. If it's stuck open, it will dump out fuel. The rail is held in by two bolts on each side of the lower. If it's stuck open, then that would explain the dumping of the fuel into the oil. Most likely the injectors are old. Check your plugs to see if any are wet. Check your exhaust to see black smoke.

If your ACT sensor was bad you'd get codes 24, 54 or 64

Five.Oh : 1987-1993 Foxbody Mustang EEC-IV Error Codes

I'd get a different mechanic.

 

[BuckSatan]

pull the vacuum line off the FPR and smell it- if it smells like gas then the diaphragm inside is most likely broken, You can also hook up a hose and a vacuum gauge or just suck on the hose and put your thumb over the hose and see if it holds vacuum- you should feel it pulling on your thumb. You can remove it with the upper on but you have to use an allen wrench to get the bolts as they go in from the bottom.

I did that previously, and didn't smell any fuel and the vac line was holding pressure. I also hooked up a fuel pressure gauge, and it seemed ok.. Maybe a little higher (41/42, as I recall) with the FPR disconnected but was right in line with it connected... So, FPR is probably not the issue...

Easy way to check injectors- take a long wooden handle or screwdriver and place the tip on the injector and the other to your ear. You should hear it clicking on and off.

Yes, I've done that too, and they all click.

Dump a can of Techron in a full tank of gas and that may free up a sticky injector. Another way is pull out an injector one at a time, crank the car with the coil wire grounded and hold the imjector over a cup. If it's stuck open, it will dump out fuel. The rail is held in by two bolts on each side of the lower. If it's stuck open, then that would explain the dumping of the fuel into the oil. Most likely the injectors are old. Check your plugs to see if any are wet. Check your exhaust to see black smoke.

That seems like the next step. I am semi-handy with the fox mustang, just some things scare me off... Such as taking the upper off on an engine I care about.... I did it before on the stock engine. That was easy as I didn't care about damaging it (It was already damaged) and I didn't have to put it back together. .I may have to do it again, though.

 

[BuckSatan]

Well, Since I was going to take the temp sender out to apply new teflon tape, I figured i'd try a new sender... This one is showing the temp higher than the middle, up towards the "o" in normal. Every so often it will drop to the top of the "r" but it's fairly consistent. This makes more sense to me than dropping from the middle. I'll have to bring it in and have it checked - I fear it's the head gasket even more now.

 

[BuckSatan]

Well, I don't want to bring it in... so, I rented a block tester from autozone, and I apparently don't have a bad head gasket... At least not one leaking exhaust gasses into the cooling system.

New temp sensor shows that when idling, the temp is nearly normal (in the middle). When driving, the gauge climbs to the "o" in normal. That and the fact that the radiator doesn't seem to get uniformly hot (driver's side seems to stay cooler than the passenger side), makes me think a blockage in the coolant system somewhere? Would that cause a loss of coolant when driving? Odd coincidence that it started with the removal of the temp sender, though...

Next step- maybe a flush and refill?

 

[mikestang63]

check for

• air in the system
• stuck thermostat
• collapsed hose
• blocked radiator

 

[BuckSatan]

check for

• air in the system
• stuck thermostat
• collapsed hose
• blocked radiator

Thanks.

Air in the system makes a lot of sense. I did fill through the hole (overfilled actually) of the temp sending unit, as you previously suggested. Could this still be an issue? This is one stubborn air bubble if so.

I was thinking of removing the thermostat and driving without to test. I would probably just drain, remove the thermostat and refill the coolant. The radiator is fairly new, but always a possibility...

 

[mikestang63]

The hot coolant comes in from the thermostat and then into the upper hose on the passenger side and then throgh the radiator and then out the driver side hose to the water pump. That is why the drive side is cooler.

• If the lower hose is collapsing then it is restricting the flow back to the water pump
• if the thermostat is sticking in a closed or semi closed position that will restrict the flow
• if the thermostat is stuck open, the coolant does not have suffficient time to flow through the radiator and dissipate heat
• Did
  
• if you have air in the system then it will create a hot spot
• if your overflow is missing, the tank is cracked, the hose kinked or blocked then that will cause the temp to be higher.

• If there is a leak in the system then that will lower the boiling point
  
• If the cap doesn't hold pressure that will lower the boiling point

Go buy a Lisle funnel as I said in my first post. and fill the system.
Pressure test the system and cap
Hook up a real gauge as the stock ones are terribly inacurrate

 

[BuckSatan]

Thanks again. Just purchased the filler kit and should have in a week or so.

Air bubble makes the most sense... Seems to be such a coincidence that it all started with simply removing the temperature sensor and coolant blowing out of the overfill for it to be thermostat or something else.

 

[BuckSatan]

I drained and flushed the radiator put in a new 180 thermostat and refilled with water. The temp needle is right in the middle (very slightly higher or lower), the rad cap is getting warm and the radiator seems to be warming up consistently... Not sure if draining the radiator got rid of an air bubble or the thermostat was having issues but either way, it seems to be fixed. My new Lisle refill kit should be here Monday and i'll refill with a 50/50 mix. Thanks for your help Mike.

Now to just figure out the gas in the oil.. Still have some fear of taking that upper off, though. If I do happen to get brave, i'll post a new thread, as I am sure i'll need some assistance.