heater bypass rover engine

poo slinger · Post by **poo slinger** » Tue Mar 06, 2012 7:42 pm

i am having trouble cooling my car when not moving and i think i have too much water bypassing the rad

i do not have a heater, insted i have a bit of 15mm copper pipe (with silicone hose elbows each end) to link the back of the inlet manifold and the heater take off / return on the water pump.

on the 15mm copper pipe i have put an isolation valve on. these have in internal diameter of about 8 - 10mm

is this too much? the valve can be restricted further but i don't know how many litres per min it should flow to stop the rad being bypassed too much.

ramon alban · Post by **ramon alban** » Tue Mar 06, 2012 9:47 pm

Hello Poo,

One has to assume the thermostat is fully opening, of course and you do not have any air trapped in the system.

Bearing in mind the location of the water pump and it is dragging water from the radiator through large diameter pipes, I think your problem may not be the heater bypass pipe diameter. But sure, it could be further reduced in diameter as an experiment.

Alternatively, it may be poor flow thro the rad and block due to crud in the system and/or worn impeller blades on the pump.

To eliminate the possibility of crud you might consider flush/reverse flush of block and rad using a mains water hose at domestic pressure.

On the other hand your coolant flow and stat and pump may all be just fine, which now brings into question the size of rad, and the choice /efficiency of the cooling fan plus how much fan cowling is still in use, compared to the original Rover installation.

You may wish to read this

http://www.vintagemodelairplane.com/pag ... emp01.html

offering information regarding choice of stat and relative efficiency of the cooling components.

Then this regarding RV8 cooling system fault diagnosis and resolution

http://www.vintagemodelairplane.com/pag ... ing01.html

For trapped air, there are various solutions, this is mine

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

Most of the above will apply to whatever your installation is, or is adaptable.

mgbv8 · Post by **mgbv8** » Tue Mar 06, 2012 9:54 pm

poo slinger wrote:i am having trouble cooling my car when not moving and i think i have too much water bypassing the rad

i do not have a heater, insted i have a bit of 15mm copper pipe (with silicone hose elbows each end) to link the back of the inlet manifold and the heater take off / return on the water pump.

on the 15mm copper pipe i have put an isolation valve on. these have in internal diameter of about 8 - 10mm

is this too much? the valve can be restricted further but i don't know how many litres per min it should flow to stop the rad being bypassed too much.

As Ramon says.
I think you could close that valve 50% or however much it needs to make sure you have a trickle of water through it to make sure air is vented.

Tell us about the cooling system?

Electric fans and fan thermostat ?

What temp rating is the mechanical thermostat and what temp are the fans set to operate at?
And where is the sensor for the rad fans ??

poo slinger · Post by **poo slinger** » Wed Mar 07, 2012 12:38 am

rad fan is on a switch, i turn it on when in traffic. i think its 14"

radiator is brand new, its about 450 x 650 3 core.

water pump is brand new.

i think the themostat is 82 degree's altho not 100% sure on that.

it could be an air lock, i will try clearing that.

Ian Anderson · Post by **Ian Anderson** » Wed Mar 07, 2012 6:32 am

Unless you have an incredibly fast fan I do not think you will be moving enough air and thus enough heat away from the radiator

Twin 12 or single 16 inch fan would be a minimum in my opinion
Ian

kiwicar · Post by **kiwicar** » Wed Mar 07, 2012 11:15 am

At the risk of sounding like a stuck record what is the ducting like around the fan? you have a fan with a swept area that is about 1/3 the area of the radiator so if there is no ducting around the fan then any air that is pulled (or pushed) through can just pass straight back through the matrix. I would think you want atleast a 16" fan (450mm is about 18" so it should fit) and you want a shroud that prevents the air that has passed through the matrix from going back through the other way. Best of all would be standing the fan off the face of the radiator and using a closed duct into the fan, but I suspect there is not enough space.
Best regard
Mike

ramon alban · Post by **ramon alban** » Wed Mar 07, 2012 11:51 am

kiwicar wrote:At the risk of sounding like a stuck record what is the ducting like around the fan?

Keep banging away Mike!

Rover went to extraordinary lengths on the SD1 with their cowl and the foam draught insulation around all four sides of the rad/cowl junction seen here:

to ensue exactly what you described - that the sucked air came thro the whole radiator fin area.

The other issue that one can describe, is that if the fan is ALSO pushing air thro' the rad from the front because there is an angular component to the flow from the blades just like an airplane propeller, the air can scatter and bounce back in any direction and the flow thro the rad is gonna be pant.

Front mounted with no cowl is double jeopardy, methinks!

When sucking, there is no angular component to the air entering the radiator fins, so it all passes thro much more efficiently.

mgbv8 · Post by **mgbv8** » Wed Mar 07, 2012 8:03 pm

You beat me to it Ramon!!

I've just been looking at an over heating problem on a mates kit car. He bought it from a guy who gave up trying to solve the "ENGINE PROBLEM" ???

Single 12" fan mounted about 1" off the face of the rad (pusher fan) with no shroud at all.

I happen to have a small pug twin fan unit that should fit nice and snug on the front of the rad to reduce his woes

poo slinger · Post by **poo slinger** » Wed Mar 07, 2012 9:37 pm

i have checked i have a 16" fan, pushing thru the rad. there is no cowel around the fan and i have yet to seal around the edges of the radiator.

but the main question is how much water should be going around the non existant heater matrix?? should it be just a trickle??

Ian Anderson · Post by **Ian Anderson** » Wed Mar 07, 2012 10:04 pm

In a word

Yes

DaveEFI · Post by **DaveEFI** » Wed Mar 07, 2012 10:42 pm

I'd measure the temperature in and out of the rad with a infra red thermometer. I'm not convinced a 1/2" bypass could rob the flow through the rad by much. Unless the rad itself is blocked.

ramon alban · Post by **ramon alban** » Wed Mar 07, 2012 11:14 pm

poo slinger wrote: the main question is how much water should be going around the non existant heater matrix?? should it be just a trickle??

Hello Poo, sorry I missed that out earlier!

It can be anything from full bore to zero. Why So? On SD1 Aircon cars, for example, there is a water stop valve for when the cabin system is on full cold so the cooling system has to cope with nil flow thro the matrix.

You could therefore shut it off.

The heat that would otherwise be dissipated into the cabin now has to be unloaded by the radiator. The rad is very large by comparison to a heater matrix, so whether the matrix flow is full or none, the system just adjusts accordingly.

On an unmodified original system the capacity of the radiator and its viscous fan unit (when needed) is quite capable of overcooling the engine, that's why the engine relies upon the thermostat to close when the rad/fan combo is over-cooling.

Its also why the Viscous unit varies its cooling effect according to the actual temperature it senses centrally at the rear of the radiator.

Too hot, and the fan speeds up. Too cool, and the fan slows down.

Now, with your highly modified system the management of excess heat has to be completely different, and totally alien to the original setup.

It seems what we have to comprehend here is

1 smaller radiator

2 no heater matrix

3 a driver controlled electric fan

4 no cowl,

5 fan pushing air thro' the rad from the front.

All those issues have been discussed variously already, and in truth, your problem is really nothing to do with the bypass, it has to do with the apparent inefficiencies built into your cooling system.

So without changing the layout, what can you do - bearing in mind you have new components that are not blocked with crud?

Your starter for 10.

1 make the leccy fan thermostatically controlled to come in as soon as the temperature in the top hose gets to about 85 degrees C.

2 ensure there is no trapped air in the cooling system

3 fit a stat with its temperature set just below that of the leccy fan

4 make sure your temperature gauge is accurate because the RV8 is quite capable of operating in the range 85 to 95 degrees C so if your gauge is telling porkies it can induce panic.

5 look for and fit a fan with maximum possible fan blade efficiency

6 if possible fit cowling.

7 Fit an air bleed schrader valve somewhere high up on the system.

8 Make sure the pressure cap is working correctly to about 15 psi, so the coolant boiling point is raised to about 130 degrees C, thus preventing any internal steam being generated by the hot spots around the exhaust manifolds at or around 100 degrees C.

9 look for ways of venting the engine bay of very hot air - louvres or similar.

10 Re-read all the material suggested, most of the above being covered therein.

So lots of things to do!

poo slinger · Post by **poo slinger** » Wed Mar 07, 2012 11:19 pm

it all sounds good, i have been thinking about air in the pipework as there is 1 bit that is a bit high.

can you get a bleed valve that will go into a silicone hose???

i have thought about ducting air from the rad down underneath the car as don't want to put vents in the bonnet. i know you still need air flow round the engine but what do you think about ducting downwards???

spend · Post by **spend** » Thu Mar 08, 2012 8:54 am

Does the car cool if you raise the RPM?

ramon alban · Post by **ramon alban** » Thu Mar 08, 2012 11:13 am

poo slinger wrote: i have been thinking about air in the pipework as there is 1 bit that is a bit high.

can you get a bleed valve that will go into a silicone hose???

i have thought about ducting air from the rad down underneath the car as don't want to put vents in the bonnet.

i know you still need air flow round the engine but what do you think about ducting downwards???

Its very difficult to know without some pictures of your set-up, Poo?

Also I am speaking to your issue in generalities. I never had to deal with these problems on my cars but from extensive study of the RV8 SD1 cooling system I sorta know how it works and what upsets the efficiency of the original system.

So with your long list of system abnormalities, compared to the original design, my suggested solutions are to try and work on possible compromises because, clearly, you cannot revert.

For bleed valves I would search google or ebay for ideas,

https://www.google.co.uk/#hl=en&gs_nf=1 ... 1398ae58d2

http://compare.ebay.co.uk/like/11070870 ... s&var=sbar

or go to a local radiator repair vendor (yellow pages) and talk to them. Bet they have one right off the shelf. Remember its only 15 psi.

I'm not so sure about the business of air flow around the engine, bearing in mind that the air driven rearwards by the fan is bluggy hot already.

I could very well imagine that ducting the hot air downwards and away from the engine would be very helpful, same as ducting or deflecting in cool air from outside the Engine bay would also be helpful.

My son solved a similar heat extraction problem on his RV8 Lada Coupe road legal dragster, when mounting the radiator and silencers in the boot and ducting air inwards using filing cabinet drawers fabricated into scoops let into the boot floor and likewise outward vents on the boot lid.

I recall loadsa pipes and fans also being involved. Needs must, there is always a way!

Not too good for keeping the cool box in, tho'.

Remember, heat retention is the problem, so anything that gets it away to atmosphere or bring in cool air has to be beneficial.

But making it invisible or pretty - who knows?

I'm sure race engineers are using ducting as a weapon against heat. Just dunno how they do it tho'.

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