Aftermarket heat exchanger question

[Rustic Charm]

I have a VP 2003T of which this year I replaced the heat exchanger with a Bowman EH 100 with a built in header tank.

I'm having problems with a damn persistent leak of coolant coming from the cap. Initially it was coming from the small copper tube which I think is an overflow tube. But I plumbed that into the body of the coolant and now I think the pressure builds up and then comes out the cap.

Given that the unit has its own header tank does anyone know why it has the copper tube which you can see where my hand is in the picture. Where should this be plumed to.

[sobraon]

The tube is for the overflow and should be plumbed to an overflow (expansion) tank. The same as you will find on a cars radiator. As the coolant heats it expands and a small amount will flow to the tank. As the engine cools a vacuum is created in the cooling system and the coolant is drawn back into the system via the middle valve of the radiator cap. .

[Rustic Charm]

Originally Posted by sobraon

The tube is for the overflow and should be plumbed to an overflow (expansion) tank. The same as you will find on a cars radiator. As the coolant heats it expands and a small amount will flow to the tank. As the engine cools a vacuum is created in the cooling system and the coolant is drawn back into the system via the middle valve of the radiator cap. .

sort of defeats the purpose of having a combined heat exchanger then. I would have been better off not having a combined header tank and just using the header tank that was originally on the Volvo.

Are they easy enough to find then?

[Rustic Charm]

This sort of thing?

[Zach]

Yup... Install one of those beside the engine and hook up the hose.

Cheers,

Zach

[sobraon]

The tank above is exactly what you need. I don't understand what you meant by "sort of defeats the purpose of having a combined heat exchanger then." The expansion tank is an integral part of the cooling system. If you look closely at the radiator cap you will see the vacuum valve that allows the return of coolant. A lot of people don't realise it exists. With the system working correctly the tank makes it easy to check on the water level usage of the system.

Make sure the tube supplied goes from the brass tube all the way to the bottom of the expansion tank. Otherwise the system will not be able to redraw the coolant. You will find that there is possibly another hose that is an over flow for the expansion tank in case of a over heating.

[deblen]

Hi
Coolant definitely needs a place to expand,but you make a good point.The Bowman looks like it was intended to be the expansion tank,as well as a HX.
This suggests you may be over filling the Bowman,thus leaving no expansion room?
If this is the intended design,then the spigot under your rad. cap is just for "boilover" release,& should never pass anything,unless severe over heat occurs.
In the old days,before expansion/capture tanks,car & truck radiators had a larger top tank incorporated in the rad.When filling the rad.,a space for expansion was left.Only if a boil over occurred,the coolant ran out the overflow spigot,in rad.cap neck,down a small rubber hose,& on the ground.This didn't fit with enviromental,so the plastic see thru over flow catch tank appeared.
Did you save your old VP tank?
Cheers/Len

[Stu Jackson]

Originally Posted by Rustic Charm

This sort of thing?

or a simple Rubbermaid quart bottle will do just as well.

[Rustic Charm]

Originally Posted by deblen

Hi
Coolant definitely needs a place to expand,but you make a good point.The Bowman looks like it was intended to be the expansion tank,as well as a HX.
This suggests you may be over filling the Bowman,thus leaving no expansion room?
If this is the intended design,then the spigot under your rad. cap is just for "boilover" release,& should never pass anything,unless severe over heat occurs.
In the old days,before expansion/capture tanks,car & truck radiators had a larger top tank incorporated in the rad.When filling the rad.,a space for expansion was left.Only if a boil over occurred,the coolant ran out the overflow spigot,in rad.cap neck,down a small rubber hose,& on the ground.This didn't fit with enviromental,so the plastic see thru over flow catch tank appeared.
Did you save your old VP tank?
Cheers/Len

Yes, I still have the Volvo one, but that had a 3/4 exit underneath it, so I don't want to use that.

The Volvo Penta 2003T had a pressure line off the thermostat housing which led to the bottom of the filler tank. But because I've replaced the heat exchanger with a Bowman that has the header tank built in, I ran the line where the thermostat is to the side of the Bowman tank.

[Rustic Charm]

Can anyone suggest if I can mount the new pressure tank below the Bowman? It's just the Radiator cap on the bowman is in the highest spot in the engine bay as it is. I can't mount anything above it, there's no room.

[deblen]

Originally Posted by Rustic Charm

Can anyone suggest if I can mount the new pressure tank below the Bowman? It's just the Radiator cap on the bowman is in the highest spot in the engine bay as it is. I can't mount anything above it, there's no room.

Hi
I don't know if,or how much lower you could mount a coolant recovery tank,& still have coolant siphon back up into HX when things cool down.I suspect it would be an over flow collection tank period,that would have to be manually emptied.
My question is why is the HX rad.cap blowing off in the first place,unless your coolant is "boiling" & building up steam pressure enough to blow the cap pressure spring.These caps are usually somewhere in the order of 7-15 psi blow off.
The other possible reason as I said before is that your Bowman is too full,& doesn't have any "cushion" space to allow the natural small expansion that all coolant requires as it warms up.
Could be all wet,but ..... Cheers/Len

[a64pilot]

First you want an expansion tank, they are a good thing in that they keep air out of your cooling system, and air (oxygen) causes corrosion, they are very cheap, or easy to make.
Ideally they should be mounted about level or above the cap, but up to a couple of feet shouldn't hurt. In theory I believe a pure vacuum will lift water over 400 inches, but your not going to have a pure vacuum either, but surely a foot or so shouldn't hurt.


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[MarkSF]

Originally Posted by deblen

Hi
Coolant definitely needs a place to expand,but you make a good point.The Bowman looks like it was intended to be the expansion tank,as well as a HX.
This suggests you may be over filling the Bowman,thus leaving no expansion room?
If this is the intended design,then the spigot under your rad. cap is just for "boilover" release,& should never pass anything,unless severe over heat occurs.
In the old days,before expansion/capture tanks,car & truck radiators had a larger top tank incorporated in the rad.When filling the rad.,a space for expansion was left.Only if a boil over occurred,the coolant ran out the overflow spigot,in rad.cap neck,down a small rubber hose,& on the ground.This didn't fit with enviromental,so the plastic see thru over flow catch tank appeared.
Did you save your old VP tank?
Cheers/Len

The use of modern organic acid coolants requires a system where the coolant doesn't meet hot air, as this causes crystalisation. This is why modern systems have a pressurised header tank, and an atmostpheric catch tank. The catch tank allows the system to run with little or no air in the header tank, as it catches the coolant on expansion, and returns it on cool-down.

[Rustic Charm]

Originally Posted by deblen

Hi
I don't know if,or how much lower you could mount a coolant recovery tank,& still have coolant siphon back up into HX when things cool down.I suspect it would be an over flow collection tank period,that would have to be manually emptied.
My question is why is the HX rad.cap blowing off in the first place,unless your coolant is "boiling" & building up steam pressure enough to blow the cap pressure spring.These caps are usually somewhere in the order of 7-15 psi blow off.
The other possible reason as I said before is that your Bowman is too full,& doesn't have any "cushion" space to allow the natural small expansion that all coolant requires as it warms up.
Could be all wet,but ..... Cheers/Len

The cap is not blowing off. And my coolant is definately not over heating, let alone boiling. I've also tried lowering the level of the coolant, but it moves enough coolant that over 4 or 5 hours the cooling tubes of the heat exchanger are exposed, so that can't be good.

I'm just waiting for photos to upgrade, I think I have fixed the problem with the expansion tank.

[Rustic Charm]

Hi everyone, thanks for all your suggestions. This is when CF is at its best in my opinion. I think I have resolved the problem. I installed an expansion tank as recommended which I purchsed from supercheap for $21. Luckily I was able to fit it in the only free space left. You can see it in the attached picture. The fluid is about 100mm below the tank so I hope that works. This only took half an hour and then I spent the rest of the day working on a PSS seal problem, so didn't test it until the last minute. But I ran it up to temp, under load and didn't see 'any' coolant where it wasn't meant to be and the new expansion tank felt warm to the touch, so it seems to be working. I really want to test it now over 5 or 6 hours of running. You can see the new expansion test to the left of the fuel filter.

What gets me is 'what's the point of the EH100' which has an inbuilt tank, if I still have to add an expansion tank? I would have been better off paying half the cost (it was $650) and just using the original header tank and an after market heat exchange without the combined tank for $200. Now I have both a coolant tank and an expansion tank.