How to hook up a VW expansion tank

[brodster]

I bought a used radiator for my engine swap. Radiator came out of a ~98 Jetta. It is just like Creepy's in this thread: http://community.ratsun.net/topic/15318-radiator-for-a-ka24de/

 

It has no filler on the radiator, just the external pressurized expansion tank:

 

My research on here shows that a lot of people have used something similar to the summit racing in-line filler and a remote overflow/expansion (non-pressurized) tank.

http://www.summitracing.com/parts/SME-2202/

 

Then again since the system was designed to have the pressurized expansion tank, perhaps that is better to use. Not sure.

 

Either way, does anybody know how to hook up the VW expansion tank? I looked at the VW coolant diagrams, etc. but I am having trouble nailing down definite answers for my particular application. It seems like the lower hose of the expansion tank goes to the low-pressure side of the coolant system. Is this correct? Or can it go anywhere? How about the smaller upper hose? Does that just act like the overflow on an standard filler neck? Expansion tank should be mounted higher than the coolant system to bleed air?

 

Or should I toss that setup and just use the suggested inline filler from summit or equiv?

 

Thanks

 

 

 

 

 

[bananahamuck]

I am not sure how these are used on a Datsun..but on a VW the bigger hose is Tee-d into the heater coil hose ..I could snap a video if you need later..I believe the cap on top lets the coolant expand up into tank then is gravity fed back into system when cold, it is very important that cap is the right one for system..

..Also i have found that on the watercoolers ( i have )..the thermostats are 195 and the fan switch in the radiator is set at 203 degrees so they run pretty hot all the time..

 

But yours looks to be a newer model than the ones in my yard..it must be a 94 or newer ?

[ggzilla]

The reason to run pressurized is to raise the boiling point of the coolant. Otherwise if it gets to 212 degrees your coolant disappears.

[DRIVEN]

I'm pretty sure the top hose is overflow and the lower is teed in, like bananahamuck said. The electrical plug is a level senor. Yes, it will need to be mounted highest in the cooling system and that will probably the hardest part. I used the same radiator on my car with the inline filler (at the highest point) and a Mt Dew overflow bottle. Works great. The thing to keep in mind is that the hose from the filler to the overflow needs to go into the BOTTOM of the overflow tank/bottle. As the system heats it will burp into the bottle ans as it cools it will siphon back into the cooling system. As long as there is coolant in the bottle you won't have to worry about sucking in air and it will purge out whatever is in the system.

[brodster]

The reason to run pressurized is to raise the boiling point of the coolant. Otherwise if it gets to 212 degrees your coolant disappears.

 

I understand that much. The VW system has the expansion tank as an extension of the radiator due to the crossflow design and no header/fill area. So it is designed to be pressurized like the radiator. From what I have read, this can help with coolant surges, etc.

 

The external expansion/overflow tank is run under atmospheric pressure.

 

Maybe they both do the same thing, just a bit different.

 

I'm pretty sure the top hose is overflow and the lower is teed in, like bananahamuck said. The electrical plug is a level senor. Yes, it will need to be mounted highest in the cooling system and that will probably the hardest part. I used the same radiator on my car with the inline filler (at the highest point) and a Mt Dew overflow bottle. Works great. The thing to keep in mind is that the hose from the filler to the overflow needs to go into the BOTTOM of the overflow tank/bottle. As the system heats it will burp into the bottle ans as it cools it will siphon back into the cooling system. As long as there is coolant in the bottle you won't have to worry about sucking in air and it will purge out whatever is in the system.

 

So you just got rid of the pressurized expansion tank and just went inline with the overflow bottle? Sounds good and a lot cleaner.

 

I just wanted to make sure people weren't having any problems with this setup.

 

Thanks

[DRIVEN]

Yup, just like that. No problems so far. The fill point can be anywhere (radiator, engine, hoses, heater hose, etc) as long as it's at the highest point in the system. In my photo you can see that there is coolant trapped in the overflow hose. That's because with a properly working cap the hose won't lose pressure or suction.

[bananahamuck]

Found on Datsuns Northwest Canby pictures2009

....Different but the same

 

 

 

 

 

 

picture courtesy ....Carter Boad

[TENDRIL]

so it is ok to have quite the length of overflow hose, as long as your pressure cap is in working order? since i will have to run a hose from the cap here in front of the radiator and to the filler neck on the other side of the engine bay ...

 

[bananahamuck]

The OG hose is like 2-3 feet long

[TENDRIL]

by the way that over flow is out of a Mitsubishi early 2000's iirc, another bishi diamante ?  had a better profile one more cyl. like but the cap was MIA 

[datzenmike]

The over flow hose should be submerged in any open container that is large enough to hold the overflow burps from the rad. Slight heat spikes can boil/burp out a cup or more of coolant. When the rad cools, the air volume shrinks and sucks the coolant back into the rad. The cooling system most not have any leaks or this suction won't happen. The rad cap is a special design for coolant recovery and a regular cap will let coolant out, but not allow it to siphon back in. I have had a coolant recovery cap on my rad and a pop bottle for two years. Every time I check the rad it is right up to the top.

 

Keep the recovery container as close to the rad as possible and the hose as short as possible. If a long run of hose, keep the diameter small and the recovery container as high as possible. This will minimize the suction needed to draw the coolant back into the rad.

 

If your coolant recovery system is working properly, when you open the drain in the bottom of the rad it will suction all the coolant out of the recovery container first.  So don't forget to refill it enough to at least cover the over flow tube.