Do I need a rear waterbridge.

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fastdruid

Member
Messages
40
Location
UK
In my build I have to modify the front waterbridge but I've just seen this car http://www.ebay.com/itm/221496812641 and he's blocked off the rear waterbridge..... which got me thinking.

Do I need a rear waterbridge?

I'm already losing the heater and manifold heating but my only concern would be air/steam pockets, especially as my engine is a few degrees nose down.

Has anyone else removed/blanked off theirs and had issues (or not)?
 

Zuffen

Super Moderator
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Sydney, Australia
I would say yes you need a waterbridge but not necessarily the stock one.

You need to link the rear of both heads but this has been done with flexible braided hose and some creative welding.

If you think about it the water at the back of the heads has nowhere to go if there isn't a waterbridge of some description.
 

fastdruid

Member
Messages
40
Location
UK
But that's just it, the flow goes from the radiator, past the thermostat (we'll pretend the engine is hot ignore it being closed) into the water pump, into the bottom of the block, up the block, into the *front* water bridge and then to the radiator. The rear waterblock sees no flow apart from to the heater and throttle body. It's there to balance the two banks and for the heater.

So if you lose the heater and throttle body connections to the rear water bridge then there should be no flow between the two sides and the only concern then is a steam/air pocket towards the rear of the heads.

I think especially with my slight nose down engine position I can't really risk leaving it out unless I included some kind of 'bleed' but I'm still curious as if anyone else has removed it/blanked it.
 

Spinnetti

Member
Messages
338
Location
KY
I was thinking of ditching it too. for now, I just run a hose from one side to the other, but would rather get rid of it completely. When your heater is off, there is no flow between them anyway? If so, then blocking them off is no different than having your heater off.
 

Zuffen

Super Moderator
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I think you need to go have a good look at your rear waterbridge.

The heater hoses run OFF the waterbridge, they are not the waterbridge.

I've never seen a rear waterbridge successfully removed/eradicated from a UZ. I have seen them modified (as mine was) but the capacity of it remained undiminished.

If Toyota could run the heater off the rear of 1 head and not run a waterbridge don't you think they would have?
 

Spinnetti

Member
Messages
338
Location
KY
I think you need to go have a good look at your rear waterbridge.

The heater hoses run OFF the waterbridge, they are not the waterbridge.

I've never seen a rear waterbridge successfully removed/eradicated from a UZ. I have seen them modified (as mine was) but the capacity of it remained undiminished.

If Toyota could run the heater off the rear of 1 head and not run a waterbridge don't you think they would have?

Although your logic is faulty (I've modified a ton of stuff to not suffer the compromises an OEM has to consider) I looked closer at the plumbing and indeed the heater circuit is independent. On my 4cyl cars, its no problem to block off the path to the heater, but as you say, might be prudent to keep. Not mandatory IMO, but better to keep. Either way, I kept mine.
 

Alan Whitaker

Member
Messages
331
Location
Leeds
Hi.
You must keep the bridge or you will get uneven heating of the head, you can ditch the heater and block off the outlets but the bridge is a must.
Why would you want to remove it?, I don't see anything is is in the way off?

Alan
 

fastdruid

Member
Messages
40
Location
UK
I think you need to go have a good look at your rear waterbridge

I have.

UCF11_cooling_system.jpg


If Toyota could run the heater off the rear of 1 head and not run a waterbridge don't you think they would have?

As I said previously "The rear waterblock sees no flow apart from to the heater and throttle body. It's there to balance the two banks and for the heater. " It's clearly shown in the diagram as being flow arrows both ways into the rear water bridge as different to one-way into the front water bridge.

I will add to that that by having the heater and throttle body feeds running though it makes it auto-bleed. Especially as there are one from each side plus the heater off the highest point. That alone would be a good reason for Toyota running one.

The main one though would be that to run the heater off one side and not off the other would result in unbalanced heating between the banks.

You must keep the bridge or you will get uneven heating of the head, you can ditch the heater and block off the outlets but the bridge is a must.

I don't see why you'd get uneven heating as long as it was bled fully as it would just make each bank a separate inline-4.

There would be problems of course if there was a partial blockage in one side but you'd have problems then anyway.

Why would you want to remove it?, I don't see anything is is in the way off

Maybe not in your car! :) More seriously I don't need to remove it but I do need to block the heater, egr cooler and throttle heater outlets and it would be neater to block off the entire bridge than have blocked off connections.
 

Zuffen

Super Moderator
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5,477
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When my car was supercharged I had the heater outlets and T/b outlet welded up.

Looked pretty neat and didn't risk any untoward problems.

But I'd still like to see you try as I could be wrong and then I would learn something new.
 

fastdruid

Member
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40
Location
UK
I think my engine is too nose down for it to work. Too much risk of an air/steam pocket and by the time I adapt something to allow it to vent I may as well just run the water bridge anyway.

I think if you were to block the bridge and have it nose up it would be fine.

It has made me think though that as it's the highest point in the system maybe I should keep one of the connections as a bleed...
 

Zuffen

Super Moderator
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5,477
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Sydney, Australia
Now I have learnt something!

I've never seen an engine installed nose down.

Engines are installed tail down to direct the driveshaft toward the diff. Plus the diff is mounted nose up to direct it toward the gearbox.

If it's nose down the front universal joint will be working at an ugly angle.

Even my rear engine vehicle (where the engine is mounted with the gearbox in front of it but driving the rear wheels) has the engine mounted rear down.

Any reason why you installed it nose down.
 

fastdruid

Member
Messages
40
Location
UK
That they are. If they're RWD with a drive shaft. Mine isn't.

It's a mid-engine RWD using an Audi 01E transaxle in a GT40 replica. The only trouble with the 01E is that the output shafts are very low so to prevent having to cut the bulkhead (the cams pulleys hit otherwise) the engine is nose down about 2 degrees.

2012-02-17%252001.00.11.jpg


It's not far off level but just enough to clear.
2012-06-05%252017.55.50.jpg


A G50 would have been an arguably better transaxle as it can run inverted with the output shafts above the input centre line to lower the engine but the price is > 10x that of the 01E!
 

fastdruid

Member
Messages
40
Location
UK
Oh and this is also why I need to alter the front water bridge in the first place, it hits on the bulkhead...
 

gloverman

Well-Known Member
Messages
3,072
Location
Hamilton. New Zealand
So you are suggesting leaving a passage of hot water that doesn't see any heat exchange of any sort to circulate around the rear of the engine by linking the heater pipes?
 
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