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Coolant leaks - cheap fix info!

54K views 180 replies 89 participants last post by  jon.k 
#1 ·
For all you folks with SVTs that leak coolant near at the thermostat housing area (if you don't have it now, you will!), here's what was wrong with mine - and how you can fix yours for $1 in 10 minutes.

There are two ports in the plastic thermostat housing that use a small O-ring to seal the port. One is the temperature sensor coming out of the top, and the other comes out of the bottom at a 45 degree angle - mine was just an aluminum plug. Mine was leaking at this plug whenever it got really cold. Some folks have leaks at the temperature sensor, same problem. Once hot, it didn't leak.

The problem is that Ford saved about $0.50 by using a Buna-N (Nitrile) O-ring to seal these ports
. Buna-N is only good for a MAXIMUM 230°F service. The engine runs constantly at just about that temperature, and hotter when you shut down after a long run on a hot day. So after a few years, these O-rings get hard and don't seal.

So, rather than pay $60 for a thermostat housing, and/or $10 for a plug (or a fortune for the dealer to fix it, if he ever does), here is what you need to know:

You need a #203 O-ring, made out of VITON. Viton is good for 450° service. Lots of places to get them. McMaster-Carr is just one (have to buy 25, costs $6).
 
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#105 ·
Hixson said:
that place is a ripoff, :thumbdown 7.50 to ship 16 o-rings? and you have to order 5.00 min? The total if you bought all three numbers is less than 4.00!
Yea, needless to say, I have a ton extra of the -109's. I've done several pneumatic projects and its hard to buy o-rings in qty 1 or 2 or sometimes even 10, the only way I know of is to get "samples" and even then you need a working relationship with the supplier. You have to understand that it cost less then $0.001 to make 1 o-ring until you get into exotic materials like Kalraz. It would be like going to the store to buy 1 paper clip.
 
#106 ·
Hi there, i just stumbled on to this page and i must say i am having a simular problem it looks to be leaking from the thermostat cover and is leaking on my tranny i have a 02 zetec wagon is the gasket that goes around the thermostat made from the same compound?
BTW it only leaks when it is cold outside can i post pics here for u guys to look at?
 
#108 ·
Update:

I have a track dog SVTF that I am overhauling, and of course it had the coolant leaks. This time, I put a dab of silicone grease on the Viton orings. WOW! It made it a ton easier to get the plugs in with the new orings.

The silicone GREASE (not spray) I got from NAPA.
 
#109 ·
I replaced my lower o-ring a couple of years ago, now the upper one is leaking. I tried to get it out today, but I couldn't.

I pulled the clip out as far as it will go, because it bottoms out on the side of the engine. Do you just have to pull up real hard? I noticed the sensor is threaded, but as freely as the whole assembly is turning, it seems like you should just pull up.
Is this correct?

Anyway, I thought it used the same o-ring as the bottom, but after reading, I need to order some 109s, that's why I didn't force the issue on removing the plug.

Thanks.
 
#110 ·
Just wanted to ask one more time. It looks like the clip that holds in my upper thermostat plug - the one with the sensor - is installed backwards.

It's leaking and I need to replace the o-ring. The clip will not come all of the way out because it hits the side of the engine. If it was facing the other way, it would not be a problem to remove. I'm pretty sure when I fixed the lower thermostat plug that the clip has to come all of the way out before you can remove the plug.

Can I just spread the clip out and remove it and ruin it in the process. Are the side slots where the clip goes open, so I could spread it. I have a pack of new clips I bought from Ford when I was changing the lower plug.

Steve, are the clips the same for upper and lower plugs? Thanks for any help. I want to fix this, this week.
 
#113 ·
So I have a Focus SVT and I believe I am having the same coolant leak from the faulty o-ring. I went out today and unfortunately picked up the wrong piece. I got the top plug, the coolant temperature sensor, and not the plug on the bottom of the t-stat housing. Could someone tell me what I would go ask for if I were to go to Ford or Autozone? Or if Autozone carries it, could you post a link for the part? Thanks in advance
 
#116 ·
I have a bag of all 3 sizes from McMaster-Carr but I've been without a Focus for a while now. I'm looking for someone to pick up the torch, agree to take my stash of o-rings and redistribute them to any member that requests one for only the cost of the envelope and shipping.

Vader80 let me know if you ordered some or not as I'm ready to ship some to you.
 
#118 ·
#119 · (Edited)
Hi guys, I found the Viton O-Ring at Advance Auto Parts. I've had to buy 2 assortment kits of these o-rings, 'cause only one each comes in these kits. But I got it done! I've removed the whole t-stat housing. It made much eisier to work with. Hope this leaking problem is over for awhile. Thanks for all the info. You guys are great!
 
#121 · (Edited)
#122 ·
#125 ·
:evilgrin:
This thread will never die
:garage:

Welcome SLVRLTNG
 
#126 ·


This isn't the cheap fix; but if you consider the number of cracked housings and time & effort you spend changing your leaking housings each time, this is the solution for you!

And there is a few other benefits to be had as well.

Now available on the website - HTPerformance Billet Thermostat Housing
 
#128 ·
As I posted earlier I can't wait till my housing cracks
I just put in a stock one a few months before you guys put this out.
It's downright pornographic!
Maybe when we all have this :rock:housing this thread will die!
 
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