Technical coolant Q's

seawalkersee

Registered User
Thought I knew it all about MN12s, then I bought a SC. This darn thing is pissin me off. I filled up the rad the other day cause it was low. I drove it for a few days and it started to push it out of the overflow. I pressured checked it in fear of the dreaded HGs gone bad but it holds ar 15 psi. Do any of you know why it pushes out the overflow? I have purged the air outta the system and think there might be more there. It was about 15 degrees when I pressure tested it. I will do it again when it is a tad warmer. to see if the temp difference will change the results.

Next. The other reason I thought it had a bad HG was because it is cold when I drive it the temp usually stays between 170-180ish at nite and 180-190ish during the day. A few days ago I had the defrost on (so the fan was running) and the bastage got up to like 220. I do have pullies but since sealing the system and making sure it does not leak I figured it would stay more consistant.

Chris
 
mine did the same thing you have to fill the overflow tank when the engine is at normal operating temperature. There is a line indicating how much coolant to add. It sucks it in when it's hot then spits it back into the overflow tank when it cools down.
 
My 93 was doing the same thing and could not find out the cause. Did many pressure checks @ 28 lbs!!! And never loss pressure. Mine would only do it under boost. Finally did a sniff test in the coolant and found exhaust gas. Ended up with a micro crack in each head on same intake valve seat. Had to do two pressure checks to find them. Would only push combustion gas into coolant under heavy boost. Do a sniff test on your coolant. I bought a kit at NAPA for $50 bucks has plenty to do several tests or a garage could do it for about $30. Hope it comes out clean for you. The car perfect this whole time, no overheat, smoke, nothing….
 
Actualy the coolant will go into the overflow bottle when the engine gets up to temp. The coolant goes back into the system from the overflow bottle when the engine cools down and not as earlier described. When the coolant heats up it expands and needs somewhere to go, hence the overflow bottle.
You're not out of the dreaded HG woods yet as I've seen many HG's that are just starting to go which do what you describe. But you could have some slight cracks as has been earlier mentioned as well.
Ford really droped the ball on the SC's cooling system and every SC owner eventualy pays the price for it. But there's been an answer for that problem for about a year now. :)
 
Jake said:
I guess that's why I haven't solved my problem yet.

Whats wrong? Give me details and maybe I can help or at least point you in a direction. I've got lots of research into the SC's cooling system.
 
I was filling the overflow tank when the engine was hot. Won't be doing that anymore. Can i pm you about your radiators?
 
Mike, I hope to get with you next year about may for a new rad. I know you heard that mid year this year but when the wife says "We need to talk", it puts things on hold for a while...

I do have the sniffer test in my box but have not used it yet. The car only makes 10 psi boost so I figured settin the p-test at 15 made me good ta go. I havent had the problem since the first of this post (havent run it hard either), so I hope it was just a fluke. This is not the first time this has happened but they are usually days where the temp has a great fluctuation 50 deg one day 15 the next. Last time it was opposite 65 deg one day and like 90 the next.

Has anyone made a rear head heater line for the sc yet? I have seen them for the 4.6 and was wondering how valid that would be to install to get the temp even.

Chris
 
Chris Walker said:
...

Has anyone made a rear head heater line for the sc yet? I have seen them for the 4.6 and was wondering how valid that would be to install to get the temp even.

Chris

Are you talking about a rear line connecting the left and right bank of heads? Do our heads flow in a way that would allow such a connection to be of value?
Mike?
 
Well as you know there is no coolant crossover pasage cast into the stck SC lower intake manifold so the only way to do that would be drilling and tapping the heads into the water jacket. You could then install AN hose adapters and run braided stainless hose tying the 2 heads together. I really feel that that is a big contributer to blowing the HG's so easily on this motor, its supercharged and it could really use the extra circulation on those back cylinders. Which cylinders sealing (HG) usually blow the most? ;)
I will be testing this theory out on my own engine once I can drive the car again. The hardware is built but some other things need to come together first before I can even put it to the test.

Let me explain why your pressure test may not be the final word on your HG's.
2 times in the past I've run into engines that do just as you describe and the first thing I do is the pressure test. The tests both times came out good just like yours did, but I later found the HG's to be gone anyway and this is why.
Sometimes the HG's fail in a way that the combustion pressure leaks into the water jacket. When that happens you get air bubbles coming up in your overflow bottle. The bubble stream might be small and really seem like much but as the leak gets bigger so does the stream of bubbles. Eventualy the bubble stream becomes so big it forces coolant out of your overflow bottle.
OK logic says that if you have a leak into the water jacket then you also have a leak of the water jacket back into the combustion chamber correct? Well 98% of time this is correct however sometimes the leak is acting like a oneway valve(or checkvalve) and when you pressure up the water jacket for the pressure test you actualy shut the checkvalve the leak has made which allows the cooling system to pass the pressure test.
Your mentioning that it has stopped acting up right now but that your being carefull and not getting the boost up much is very telling. Both of the engines I seen that acted like yours drove around perfectly normal and the temps were normal as well, however the overflow bottles kept running low.
Once the engines were out on the highway and speeds were up to 55-60 MPH the engine temp would start climbing real fast. I say 55-60 MPH because 1 engine started overheating fast at 55 and the other did the same thing at 60. I dont feel that speed played a part in any of this, I really think it had more to do with the cylinder pressures the engines were having(one was hitting higher pressure sooner).
HG's can blow in several different ways causing several different symptoms.
 
Here is a thread on the TCCoA that has a picture referencing the freeze plugs on the rear of the 4valve heads.

http://forums.tccoa.com/showthread.php?s=&threadid=33475

I guess the question I was wondering is how the water passages are setup for the flow to occur in our heads. Do both heads dead end at the back?

Wynn might also have info on this since he's hacked a head apart.

I notice more threads all referencing Brian at Apten. Hmm, I don't recall Brian saying anything about doing this on the SC heads.
 
Yes Mike that TYPE of system is what I'm talking about.
But I wonder why they went to the trouble of mounting all that on the backside of the heads like that. Theres clearly 2 boss's cast into the heads where the intake manifold faces up, see em?
Drill the boss's out drill and tap one more bolt hole per head and you can bolt up flanges with adapters right there where its easier to get to.
Thats what I've done on my engine, except its attached on the intake manifold where the 2 rear coolant crossovers are cast into the heads.
 
Thanks Mikes. As for the head crossover yes that is what I am speaking about. Does the one you make flow into anything or just connect the heads together. I personally think there is a problem with that one in the pic because it will (or seems to look like) it is creating a "dead space" there are to many pressures running into each other. One can not flow into the other one without the other not moving adequate amounts of aqua.

And with having just a crossover, will that flow enough water? I am gonna chem test for exhaust gasses. I already know the outcome it is just my luck. I may have to have you show me the correct way to make the crossover mike.

Chris
 
The bullhead on my T in the crossover feeds the heatercore. Sure water flows through there Chris, just take a look at the front of the motor. You have the same setup there. The crossover passage in the intake tying the 2 heads together with a thermostat in the bullhead of that T configureation. The output of water from that bullhead feeds the radiator, the heatercore is just a small radiator itself. Any flow of water you get there can only be helpfull in getting the hot water out of the engine and replacing it with cooler water. Without an alternate route for coolant to move around in the rear of the heads the coolant tends to eddy and linger too long thus that part of the engine runs hotter than the front. Simply tying the 2 heads together at the rear will not improve the water circulation, but ty them together and then give the coolant another route to take in order to get out of the engine and I believe you'll see some substantial cooling improvements.
 
Pic? What size hose did ya use? Ford really dropped the ball with these cars. They have soo much potential and yet I feel as if we have just scratched the surface of how good these cars can be.

Chris
 
Thanks for the info Mike. I'm thinking they did it the way they did to make an easy bolt on kit for people. Just yanking existing freeze plugs. I believe the items the bolted to the block are just pressed into those holes and not threaded into them.

Any idea on when you might see some results from this? I'm going to have my engine out shortly for machine work and it might be something to try. At the very least I could have the holes made and tapped and put plugs in them for now. What size do you recommend for the fitting?
 
Sooooo...what size are the an fittings you used Mike? Did you use an AN fitting in the intake and then another AN fitting on top of that one (90 deg), or did you just use the 90 deg stright into the intake?

Chris
 
I'm sorry, I had forgotten about this thread.
Chris my intake has a crossover passage built into it that ties the 2 rear coolant ports together. I then come out of the rear passage with an AN 10 to 3/4" NPT male adapter. I TIG welded AN 10 bungs to the heatercore nipples and ran the stainless hose to the adapter in the manifold.
 
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