Help: How do I hookup my Coolant Overflow Tank?
 

I just finished the S5 TII into S4 N/A swap and now I have no filler cap and no place to hookup the coolant overflow resevoir.

I found out the hard way that the S4 waterpump neck does NOT fit. (Can you say hand me a drill and tap & die set).

I have a small coolant leak somewhere and I am very sick of having to pull out the water-level sensor and fill in that tiny hole.

Is there anything I can do to add the filler cap and hookup for the overflow tank aside from getting a new Rad?

Worst case scenario - http://moroso.com/catalog/categorydi...?catcode=29014

Does anyone know if it is harmful not to have the overflow hooked up? When the coolant is pressurized, where would it go as it expands?

can u take a pic? my coolant overflow line comes off the top of the radiator.

Apparently some of the S4's had the coolant overflow line coming off of the rad, but mine had it on the thermostat housing/neck so there is none on the rad.

http://mazdatrix.com/Pictures/b-water/RadCap7.jpg

dont know if this fits on the s5 piece though. your rad should have a nipple on it

Looks like it would fit perfectly on the top of an S4 filler neck which I can't use. I could cut out a spot on the top of the rad and super-glue it, but somehow I don't think that would be the best idea :).

Also, I am still using the S4 N/A rad. The overflow tank previously hooked up to the nipple on the neck not on the rad. However, if there was a second nipple on the rad, that would be life-saving. If so, where would it be?

Yes, you MUST have provision for expansion/overlow!
 

As you have discovered, you have mismatched parts from two different cars-and you are missing the fill cap and overflow nipple.

You have two choices: either

1)put in an after market rad that has the filler neck and overflow nipple, or

2) use that clever Moroso rig that someone linked to in an earlier post.

Personally, I would upgrade the radiator, since the N/A rad is unlikely to be able to handle the heat from the TII. PM SpooledupRacing, He has a nice affordable all metal rad that should fix your problem, upgrade your cooling capacity with an OEM fit. You won't have to sell a kidney to afford it...

Your small coolant leak is most likely caused by the fact that there is no place for the coolant to expand as the system heats, therefore forcing it's way out of the system somewhere.

But I am guessing that you already guessed that when you posted, since you noticed that the neck and the nipple was missing.:)

The stock NA and Turbo radiators share a common cooling matrix- the only difference is the fittings/caps.
Upgrading the rad is a good idea but the Turbo version is not in and of itself an improvement.

Ok, so what I did was made the S4 filler neck fit. It does cover the thermostat, but it is close. It might have helped a little that I had to drill out and tap a new hole as I broke off one bolt already so I tried to move the hole a tiny bit upward. I also had to find different bolts as the S5 ones are too short for the S4 neck. You do have more of the neck sticking out of the bottom and less coverage on top. However, after letting it Idle up to normal temperature, it was fine. I then took it out and made a couple of runs up to 6k RPM and checked it with no leaks. Now, after about 30km's, it still seems good. No add coolant buzzer, no leaks.

As for the radiator, it seems to be doing fine as the temp gauge never makes it past 1/4, but that is also worrying me a little bit as I was thinking it should be closer to 1/3. It might just be that it has been in the 60's (teens in celsius).

I that right? My 88 TII oem rad seems to have an extra row-thicker core compared to my S5 vert, Quite honestly however, I haven't seen the oem S5 in a couple of years since it blew out and I replaced it so I am working off of my memory.

Thanks for the correction, assuming you are correct.:)