Convert bowman heat exchanger for header tank?

contessaman

contessaman

Well-Known Member
Joined
29 Oct 2009
Messages
823
Visit site
Hi, can anyone please give me some advice, I’ve got a bowman heat exchanger on my engine. The type that has a radiator cap that looks like it belongs on a 1970s car on it. It’s all fine and cools the engine well. But there’s one problem. My calorifier has to sit slightly above the level of the engine. It’s not difficult to bleed the system and again it works well And heats the water .
my problem is, due to the head of pressure in the system, coolant will leak from the cap in the heat exchanger. The cap has a spring in it for pressure relief and particularly after running the engine then switching it off hot it seems to overcome the spring valves in the cap and leak out.
is there not some way I can buy some kind of cap that seals where the radiator cap goes and then Introduce a plastic header/ expansion tank like in a car and have that mounted above the level of the calorifier? There’s loads of height over my engine so it’s no problem to mount such a thing if one exists.
grateful for any advice or links to available off the shelf parts to achieve what I want to . Ta
 
contessaman said:
Hi, can anyone please give me some advice, I’ve got a bowman heat exchanger on my engine. The type that has a radiator cap that looks like it belongs on a 1970s car on it. It’s all fine and cools the engine well. But there’s one problem. My calorifier has to sit slightly above the level of the engine. It’s not difficult to bleed the system and again it works well And heats the water .
my problem is, due to the head of pressure in the system, coolant will leak from the cap in the heat exchanger. The cap has a spring in it for pressure relief and particularly after running the engine then switching it off hot it seems to overcome the spring valves in the cap and leak out.
is there not some way I can buy some kind of cap that seals where the radiator cap goes and then Introduce a plastic header/ expansion tank like in a car and have that mounted above the level of the calorifier? There’s loads of height over my engine so it’s no problem to mount such a thing if one exists.
grateful for any advice or links to available off the shelf parts to achieve what I want to . Ta
Click to expand...
Hi, what you are asking for sounds like the installation as from new on my Volvo 2020D with a Quick calorifier. The "radiator cap" on the heat exchanger does have a tube up to a plastic expansion tank mounted at high level in a cocktit locker above the calorifier. Might be worth checking on Volvo spares lists.
 
johnphilip said:
Hi, what you are asking for sounds like the installation as from new on my Volvo 2020D with a Quick calorifier. The "radiator cap" on the heat exchanger does have a tube up to a plastic expansion tank mounted at high level in a cocktit locker above the calorifier. Might be worth checking on Volvo spares lists.
Click to expand...
Following my earlier reply I have found a photo online showing the same configuration as I have. In the attached the fitting between the two Jubilee clips is the Tee fitted in the radiator cap. The bigger hose is part of the circulation to the calorifier, the smaller is to the expansion tank. I guess you only need the single feed to the tank but it shows there is a part that suits your suggestion. This installation is on an Elan 333. Edit I have now found a clearer pic, apparently this time on a Bavaria
 

Attachments

Last edited:
Hi thanks for that, that’s an interesting way of doing it. Mines not a Volvo so the cap won’t fit but that’s not to say I couldn’t copy it. Equally, it’s led me to another idea, the bowman exchanger has a small tube overflow as part of the neck the cap screws in to. Presently it has no tube out of it and that’s where the coolant that’s blowing past the cap comes out from. Maybe I just need to fit a tube to this and take it up higher than the calorifier? Either as a stand alone tube or perhaps with a small tank that I use to top the coolant up with ? It it would mean there’s no air space in the system which doesn’t allow for any expansion so might not be right ...
 
contessaman said:
Hi thanks for that, that’s an interesting way of doing it. Mines not a Volvo so the cap won’t fit but that’s not to say I couldn’t copy it. Equally, it’s led me to another idea, the bowman exchanger has a small tube overflow as part of the neck the cap screws in to. Presently it has no tube out of it and that’s where the coolant that’s blowing past the cap comes out from. Maybe I just need to fit a tube to this and take it up higher than the calorifier? Either as a stand alone tube or perhaps with a small tank that I use to top the coolant up with ? It it would mean there’s no air space in the system which doesn’t allow for any expansion so might not be right ...
Click to expand...
contessaman said:
Hi thanks for that, that’s an interesting way of doing it. Mines not a Volvo so the cap won’t fit but that’s not to say I couldn’t copy it. Equally, it’s led me to another idea, the bowman exchanger has a small tube overflow as part of the neck the cap screws in to. Presently it has no tube out of it and that’s where the coolant that’s blowing past the cap comes out from. Maybe I just need to fit a tube to this and take it up higher than the calorifier? Either as a stand alone tube or perhaps with a small tank that I use to top the coolant up with ? It it would mean there’s no air space in the system which doesn’t allow for any expansion so might not be right ...
Click to expand...
Is the small tube you refer to not on the outside of the seal, hence water blows out of it when the seal is lifted by excess pressure but I don't see how it would let coolant back from the header to the heat exchanger?
Sorry if I am off the mark. Why not cotact Bowman? It's years ago now but I do recall them being very helpful when we had an issue on a previous boat.
 
Rappey said:
The solution is to replace the heat exchanger pressure cap with a stainless one with no spring ,allowing the water to exit via the small overflow at the neck ,through a small rubber hose to your expansion tank, which has the space for expansion and a pressure relief cap.
Aeroline Stainless Steel Radiator Rad Blanking Cap For Cars With Expansion Tank | eBay
Click to expand...
I have a similar problem to Contessaman’s and this cap would seem to provide an ideal solution. The Bowman blanked off with one of these caps and a pipe taken from the Bowman’s small overflow tube up to a header tank which has a pressure relief cap (Volvo type?) would be a practicable solution. At the moment I collect any overflow in a bottle to prevent it contaminating the bilge but of course it doesn’t get sucked back into the system.
Does anyone know if car type radiator caps are produced to a standard size/configuration?
Mike
 
Those type of radiator caps is a one size fits all as far as I'm aware. The differences would be the spring/pressure release rating.
I also have a bowman heat exchanger and was fed up of the caps corroding and leaking so went with the stainless and expansion tank option.
 
The expansion tank sits higher than the engine. It even has the same spring radiator type cap as the bowmn .. It has a small pipe exiting under the cap just like the bowman so that is now my overflow pipe. A small ruber pipe now goes from the bowman overflow pipe and connects to the bottom of the expansion vessel so fluid is free to expand into the tank and gravity feeds the bowman
 
Thanks rappey , so youre saying if I fit that cap you sent a link to in eBay to my bowman, then put a pipe on the bowman overflow and take it up high to an expansion tank... this will do the trick? Is that right ? I’m blessed with loads of room in my engine bay I can certainly mount a header tank so that it’s the highest thing in my system and be above the calorifier
 
It certainly works for me. My calorifier is also higher than the engine and I have a car heater matrix in the same loop for lovely hot blown air.
I was a little concerned that either the engines fresh water pump wouldn't have enough oomph to push water round all the extra pipework or it may have a big cooling effect on the engine but it all works very well.
 
When doing this mod remember that the water that escapes to the header tank wants to return to the engine when it cools down. You need a radiator cap that as well as the spring loaded relief valve has a non return valve built in which allows this to happen. They are standard in many cars.
 
Reviving an old thread I know but…
I have a header tank but it takes one of those small Japanese style radiator caps and I can’t find one that’s rated 10psi (0.7Bar) . The best I can do is 13psi(0.9Bar). Any thoughts on where to get one at 10psi or am I ok to put a 13psi rated cap on my expansion tank. It’s for a Bowman heat exchanger on my Perkins 4.236.
Thanks
 
You must log in or register to reply here.

Share this page

Top