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Discussion Starter · #1 ·
I've recently fitted a Radium coolant expansion tank, with cap. I have a problem with it holding coolant - fluid seems to be dumping from the drain hose to the point where the expansion tank empties itself eventually causing a marked increase in coolant temps when vehicle is stationary. I then have to refill.


I can accelerate the dumping by performing some data-logging, or chasing a Hellcat Widebody on the freeway during my afternoon commute yesterday (120mph+).


During high speed runs, what happens is coolant completely flushes out of the tank via drain hose and completely soaks my passenger-side wheel well, wheel, tire, suspension, brakes, and the entire side of my car, and the Hellcat behind me (heh).


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I've contacted Radium and they've been very responsive. We're going back and forth and they mention it's normal for coolant to dump from the drain hose until system level is stabilized, but I don't think it's normal for the expansion tank to completely dump itself like this on a regular basis. The cap they sell has a spring and it's rated to open at a certain amount of pressure.

I plan on having the system tested (including the cap), but until then I figured I'd ask if anyone here has had the same experience? I'm hoping it's something simple and not internal to the engine.
 

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Discussion Starter · #2 ·
Another question that might be relevant here.. is there any possibility my cooling system would over-pressurise?
 

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Looks like this is the newer designed one since the fitting is newer as well.

where is the sight hose to see the level?
 

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The expansion tank should not overflow, you could run the car without the expansion tank cap and it should not overflow. If you notice a strong correlation between coolant overflow and high loads, like you make a quick pull and water starts flowing right away, I'd be concerned about cylinder head sealing...
 

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Discussion Starter · #6 ·
The expansion tank should not overflow, you could run the car without the expansion tank cap and it should not overflow. If you notice a strong correlation between coolant overflow and high loads, like you make a quick pull and water starts flowing right away, I'd be concerned about cylinder head sealing...
Since yesterday when it emptied and I made this post I have not refilled it (as I usually do). I drove to work and back today, no real boost events.. temps seemed fine. And no leaks that I could observe.

There happened to be a 1/4 full in the expansion tank when I arrived home, which was a surprise to me. I thought all the coolant had dumped out yesterday because the sight tube displayed an empty tank.

I wonder if the dumping was just the cooling system equalizing? (Admittedly I am clueless about cooling systems). I'll keep an eye on it and update here. Crossing my fingers.

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In the meantime, can you please tell me more about cylinder sealing and how it affects pressure in the cooling system, and how it may cause coolant pressure to increase to exceedingly high levels, resulting in coolant dumps like this?
 

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Since yesterday when it emptied and I made this post I have not refilled it (as I usually do). I drove to work and back today, no real boost events.. temps seemed fine. And no leaks that I could observe.

There happened to be a 1/4 full in the expansion tank when I arrived home, which was a surprise to me. I thought all the coolant had dumped out yesterday because the sight tube displayed an empty tank.

I wonder if the dumping was just the cooling system equalizing? (Admittedly I am clueless about cooling systems). I'll keep an eye on it and update here. Crossing my fingers.

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In the meantime, can you please tell me more about cylinder sealing and how it affects pressure in the cooling system, and how it may cause coolant pressure to increase to exceedingly high levels, resulting in coolant dumps like this?
One common symptom of head sealing failure (which could be a failing head gasket or a head clamping issue) is that part of the combustion pressure escapes to the coolant system, creating abnormal pressure which precisely causes the expansion tank to expel water. This typically happens a high load (high boost).

Than being said an expansion tank is not supposed to be full, precisely to give room for coolant expansion. If the coolant level don’t exceed the expected max when cold, no cooolant ever overflows, unless the engine severely overheats or the cooling system is over-pressurized due to a combustion pressure leak (or both.)
 

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Discussion Starter · #8 ·
Makes sense, thanks for the explanation! I'll definitely keep an eye on it.

I think it's a possibility because the series of events leading up to me installing this Radium tank were:

1. Track day at Thunderhill (stock expansion tank) - first session of the morning I dump all coolant out of the bottom of the tank (at this time I suspected the tank to be cracked/broken)
2. Took the car to dealership the following Monday - they confirm faulty expansion tank and replaced under warranty. They did not replace the lower hose.
3. Track day at Sonoma (new, stock expansion tank) - coolant dumps again during first session. I remove the tank and inspect, I cannot see any damage. Coolant is leaking at the hose connection to the bottom of the tank. Why would the hose connection leak? Why would Ford confirm a faulty tank in the first place? I am thinking at this point the lower hose is faulty.
4. I install Radium expansion tank - coolant still dumps during high speed runs. :/

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So, I think this is a good amount of information and I will def have Ford or some mechanic I trust to look at it, unless you can recommend some test that I can perform myself.

I appreciate the info, @axelr!
 

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One common symptom of head sealing failure (which could be a failing head gasket or a head clamping issue) is that part of the combustion pressure escapes to the coolant system, creating abnormal pressure which precisely causes the expansion tank to expel water. This typically happens a high load (high boost).

Than being said an expansion tank is not supposed to be full, precisely to give room for coolant expansion. If the coolant level don’t exceed the expected max when cold, no cooolant ever overflows, unless the engine severely overheats or the cooling system is over-pressurized due to a combustion pressure leak (or both.)
I have no heard any cases of HG failing showing those symptoms on the RS. It is always the reverse, where coolant seeps into the cylinders after the car is shut down. This washes the oil lining away and causes the scoring the cylinder.
 

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I was of the understanding, the RS has a coolant channel the Mustang lacks, so the gasket lacked an opening. The antifreeze would super heat at that spot, between the center cylinders, causing the gasket to fail, allowing coolant to migrate to one of the inboard cylinders causing the white sweet smelling exhaust.
 

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I have no heard any cases of HG failing showing those symptoms on the RS. It is always the reverse, where coolant seeps into the cylinders after the car is shut down. This washes the oil lining away and causes the scoring the cylinder.
OK so the car vomiting water through the expansion tank under high load is something normal, because some other cars has some other failure mode in some other circumstances?

Apparently the tank was changed twice, at least once at a dealership, and the water is still being expelled when the engine sees sustained high loads. Either it’s as simple as a damaged pipe, or it’s combustion pressure.

I’d pressure-test the cooling system and do a compression test at this point.
 

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Discussion Starter · #12 ·
The dealer did do a cooling system pressure test and said it was fine when they replaced the tank initially. I'm wondering do they actually test the system at a pressure that is expected of an engine operating at it's highest load?

I do have a compression tester handy, though. Perhaps I will give that a try. Any idea of what figures I should be keeping an eye out for?
 

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Discussion Starter · #13 ·
Just a quick bump for anyone who has this same kit... What is your normal coolant level? Can you usually see it in the sight tube?

@GmpaJimj I know you might have this kit?

Now that I've dumped coolant I figured I'd just leave it and continue driving. Most of the time the tank is empty and I see nothing in the sight tube. Mid-day with engine hot I might see the tank half full according to the sight tube.

Was I just overfilling the tank and it was dumping to equalize itself? Is an empty tank considered "normal" with this modification?
 

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has your cooling system been burped?
 

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Just a quick bump for anyone who has this same kit... What is your normal coolant level? Can you usually see it in the sight tube?

@GmpaJimj I know you might have this kit?

Now that I've dumped coolant I figured I'd just leave it and continue driving. Most of the time the tank is empty and I see nothing in the sight tube. Mid-day with engine hot I might see the tank half full according to the sight tube.

Was I just overfilling the tank and it was dumping to equalize itself? Is an empty tank considered "normal" with this modification?
Mine stays at 1/2 in the sight tube. That’s where I filled it to after install. Hasn’t moved.
I‘ll admit, I’m not, on it, like some though. So, that’s country sport touring vs city or track.
edit: I’ve never checked it while it was hot during a drive. I always do a pre-drive inspection..cold. I’ll have to check next drive.
 

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Discussion Starter · #16 ·
Mine stays at 1/2 in the sight tube. That’s where I filled it to after install. Hasn’t moved.
I‘ll admit, I’m not, on it, like some though. So, that’s country sport touring vs city or track.
edit: I’ve never checked it while it was hot during a drive. I always do a pre-drive inspection..cold. I’ll have to check next drive.
Good to know, thank you.
has your cooling system been burped?
Not that I am aware. The dealer performed the first expansion tank swap, says they pressure tested and it passed. The following weekend the new tank leaked at the same lower hose junction where the hose attaches to the bottom of the surge tsn. So I swapped to Radium... didn't do anything special with burping.
 

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What bleeding process did you use when you fitted the tank?

Ciao
 

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Discussion Starter · #18 ·
What bleeding process did you use when you fitted the tank?

Ciao
I drained the old tank and removed it and hoses, attached new tank, filled. I started the engine with the cap off, and ran it up to temp, keeping an eye out for fluid level dropping as thermostat opened. I do remember coolant temperature stabilizing at 178F (thermostat opening), fluid level never dropped, now that I replay events in my head.

If there is another better process here I definitely missed it (Radium instructions don't detail one other than what I described).
 

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I drained the old tank and removed it and hoses, attached new tank, filled. I started the engine with the cap off, and ran it up to temp, keeping an eye out for fluid level dropping as thermostat opened. I do remember coolant temperature stabilizing at 178F (thermostat opening), fluid level never dropped, now that I replay events in my head.

If there is another better process here I definitely missed it (Radium instructions don't detail one other than what I described).
It’s been awhile, but that sounds familiar.
 

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I drained the old tank and removed it and hoses, attached new tank, filled. I started the engine with the cap off, and ran it up to temp, keeping an eye out for fluid level dropping as thermostat opened. I do remember coolant temperature stabilizing at 178F (thermostat opening), fluid level never dropped, now that I replay events in my head.

If there is another better process here I definitely missed it (Radium instructions don't detail one other than what I described).
Not as simple as that I'm afraid. You should vacuum fill it and then the manual has a running process that involves running the engine at quite elevated rpm for a period of time. I'd need to look it up again. A vacuum fill and shop manual bleed is the first thing you should do before exploring more serious scenarios. It may not be the answer but It's only sensible.

Ciao
 
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