The V8 Owners Forum -

Hi guys I hope you can shed some light on a problem I am having. I have a tvr 350 v8 engine which has been converted over to a holley setup. I fitted a Davies craig 80 ltr a minute water pump and evrything was fine and heat came out of the heater matrix. I ran it to Santa Pod and gave it some stick, on the way home the temp started to rise and the heater matrix went cold. Well long story short we got the truck home and connected the pump to a live supply with the engine OFF to see how the water flow was behaving, when we turned the pump on it made a noise like it was generating bubbles somehow and indeeed when we took the rad cap off it was full of frothy bubbles, I thought summat had happened to the pump so I bought the next size up Davies Craig water pump 115ltr a minute and the digital controller. Fitted the new pump etc to the truck and connected it direct to the battery to get the water flowing around the system and bleed the heater matrix. As soon as I turned it on the pump made the same noise as the old one and also started making frothy bubbles in the radiator !
Now if the engine was running it could be said that it was a possible head gasket failure and air was being forced into the water ways but with the engine off and just the water pump running why would it make bubbles in the system ????? there has been no tampering with the coolant in the system by any body such as adding a frothy substance
I have no idea now what it is and I have a good 80 ltr pump sitting in the cab that i didnt need to replace any help you can give would be very much appreciated

regards Simon

If the heads gaskets are intact. I would say its air / vapour entrainment or just cavitation from the pump being quite big.
I'm not sure what the stock Rover V8 water pump would flow.
But you could be seeing a small air lock that has been churned into cream by a powerful pump which is flowing water so fast the air does not have time to settle out anywhere.

now i will be the first to admit I know nowt about cooling systems. The current system has problems and with this forums help I want to eliminate those problems. The radiator sits quite low in comparison to the engine and very low in comparison to the heater matrix, there is just a radiator with a filler cap (no sticker saying what pressure it is) and an over flow pipe that vents to atmosphere, no expansion tank or header tank. Now if you guys can say "I need a header tank or expansion tank (i dont knopw what the difference is between these two) fitted high up on the engine bay bulkhead, above the matrix pipes2 then thats what i will do, as I say i dont know beggar all about the plumbing do's and dont's so just tell me what i need to buy and its job done

regards Simon

www.hightrux.co.uk

I forgot to add that the pump speed is managed by the digital controller so when it starts up its only pulsing and not continually running, the thermostat has been removed as stated in the davies craig instructions, the temp is set by the controller and speeds the pump up accordingly and also operates the electric fan

Hi Simon
I woud suggest that you remove the highest hose running to the matrix and then fire the pump up again.You only need to disconnect at the matrix end.
This would force any air in the system to the top and then vent it out of the loop.
You can then back feed the system with a hose pipe and then reconnect and see if that works.
I know nothing about the DC pump but it does'nt sound like you have anything major going on there.
Good luck.
Cheers
Paul

Using a resevior of some form and some pipe, can set up some way of checking if this is a feature of the pump design or the cooling system? this would simplify the task somewhat.
Mike

You may have a hole somewhere before the pump. I had a similar issue with my car and it turned out to be one of the hoses was holed and the pump was drawing air into the system as it was pre-pump.

Cheers for the help so far guys its very much appreciated

as with everything in life there is always someone who adds summat new to the confusion.............. I was asking at work what people thought and one bright spark said put a swirl pot on there to remove bubbles and fit an expansion tank

wish i had never asked them now

Right, back to basics, does anyone out there have a drawing or can point me towards a drawing on the net of the right way to install a water cooling system, IE header tank/swirlpot/expansion tank hoses that are needed etc etc ?

Instead of me just plumbing bits in wildly, I would like to go about it in a semi knowledgable fashion

Cheers for the help guys

I don't agree with all of that.
An expansion tank, YES by all means, but a swirl tank I disagree. If the air is a factor of incorrect/poor flow then jack the front of the vehicle up and run it so the air will migrate to the highest point and it will all find it's way to the header and the expansion tank.
Once that air is finished/dissipated then the swirl tank is redundant and added weight and another potential point of failure.

You need to first establish if there is a leak in the system. Do a block test with the liquid that changes colour in the presence of exhaust to establish if it is a cylinder leak or not and if you have spares, swap out all the hoses and use rubber grease and new clamps to eliminate possible leaks.
You may have a pinhole in the pump body, thermostat housing or anywhere else that is allowing air into the system, and a pressure test will not pick it up. Get hold of a "vacuum pump" that can pull a few psi negative (Snap-On has one that is a standard refrigeration mechanics tool) and with the engine hot pull a low pressure in the system and see if it holds to eliminate hoses and pinholes.

I don't beieve it is a result of pockets of air trapped in the engine, I think you have a leak somewhere, 6 months ago I would have agreed but 2 head gaskets later i found my leak and since then it has been fine.

Cheers for that mate I will look into it over the weekend

Hello Simon,

First off, I know nothing of the type of system you have there, but, I am familiar with the regular/normal configuration as fitted to my 4 SD1's since '93 and without exception expelling ALL airlocks from an RV8 cooling system has never been straightforward.

From new, over time, as systems got crudded or even slightly modified, the task got harder rather than easier.

In significantly modified layouts with changed plumbing or component height, serious acknowledgement of the airlock issue has to be accepted.

Added to the mix, you have a powerful electric pump that seems (to me, at least) to be capable of pumping fluid much faster than the original water pump.

Maybe even faster than the natural flow capability of the system as a whole. If true, then the pumping function would become a triumph of power over resistance, leading to a significant propensity for the blades to cavitate.

Now add unwanted air to the equation along with sticky anti-freeze plus traces of oily contamination of the coolant and it becomes a 100%, guaran-damn-teed, bubble factory. Right from the get-go, a West Ham Fan's Delight.

Worse, in an effort to resolve the issue you substituted an even more powerful pump, creating even more cavitation, therefore encouraging even more bubbles.

Logically (in hindsight, of course) one might have thought the preferred solution would be to reduce cavitation by reducing the pump flow/power to match the natural flow capacity of the overall system..

In addition, we also know that pump speed is digitally controlled by a Gizmo which adds complexity to what is a fundamentally time proven simple system.

Does the Gizmo know (or even care) that the faster the pump goes, the worse the bubble problem gets, the less effective the cooling process becomes, the worse the temperature rises, so the faster the Gizmo wants to the pump to go!

A perfectly designed example of thermal runaway the nuclear industry would proud of.

Sadly then, you have reinvented the Wheel to come up with something square or oval which explains the bubbly discomfort.

Mind you, lets be clear, its not the pump speed/flow/cavitation that is the primary cause of the problem.

That, I venture to suggest, is unwanted air in the system.

So to eliminate the primary cause one will have to go back to basics.

Without any knowledge of your particular Cooling System layout all I can suggest is that you read my following essay on the subject of expelling air locks from a regular RV8 system and adapt it as best you can to your particular system.

http://www.vintagemodelairplane.com/pag ... ant01.html

Regarding your wish to redesign the plumbing to solve the problem, perhaps you just need to study a typical layout seen under any SD1 bonnet or other conventional RV8 application and add components such as expansion/overflow facility and pressure release, as far as is possible.

Even with an improved plumbing layout and airlocks eliminated, you will still have to match the water pump power to the flow capability of the cooling system to eliminate cavitation.

I dont suppose wishing you Good Luck and a Happy New Year helps much, but at least you get to smile a little. [/u]

Cheers buddy that is most helpful

hightrux wrote:I forgot to add that the pump speed is managed by the digital controller so when it starts up its only pulsing and not continually running, the thermostat has been removed as stated in the davies craig instructions, the temp is set by the controller and speeds the pump up accordingly and also operates the electric fan

Hoping not to add further confusion to the matter, I have the following comments.

Testing the pumps by connecting directly to the supply will cause the pump to spin at max revs, something it probably never does under normal conditions when under the control of the regulator box. The pump will be designed to run under pressurised conditions and this reduces cavitation effects. So your test in an open non pressurised system may be clouding the issue.

Removal of the thermostat is never a good thing unless you introduce a restiction ring in it's place. Reason being that pump pressure in the block/heads will not be as high as it should be and local boiling (Kettleing) will occur and produce air bubbles. In your case it seems the heater matrix is higher than the rest of the system and that where the air will end up.

So if you are lucky, the mad dash at the Pod could have cause sufficient bubbles to fill the matrix with air and or caused another airlock.
If you are unlucky, the mad dash has damaged one of the head gaskets.

I don't think you have said that you have started from scratch again and bleed the heater/system with all parts reassembled. This seems the way to go to determime if the problems reoccurs during normal driving or just when you screw the nuts off it.

My thinking being, you got to the Pod without a problem.

Regards Denis

Cheers bud, every bit of advice is taken on board I should have time to have another look at the cooling system this weekend so hopefully I should have some news to report soon