Rover V8 Cooling Advice Needed

[craig1410]

Hi,

I'm running a Rover V8 3.5 from a 1977 SD1 in my "Seven" style kit car. This car was built by myself over the last 6 years based on the "Build Your Own Sports Car for (cough) £250" book by Ron Champion.

Anyway, I'm having some cooling system issues which are spoiling my enjoyment of my now road-legal car and I would appreciate some advice.

Symptom:
Car is slowly but steadily overheating regardless of whether I am running slowly in free air (approx 50MPH) or idling while stationary. I am using the SD1 temp gauge and it is going from cold to just beyond the mark between 90 and 130C (which I think is actually 100C not 110C as you might expect) within 110-15 minutes when driving or around 2o minutes when idling stationary.

Here are some pictures of my installation from various angles:

http://gallery.me.com/craig.chamberlain#100029

Action already taken (not in sequence):
1. Flushed and refilled the cooling system
2. Re-curved the distributor as per recommendations in various RV8 tuning books. I changed the weights and removed the vacuum advance.
3. Richer needles for the SU carbs (BBW needles)
4. Fitted smaller diameter billet alloy water pump pulley. This is a P6 short nose pump and is now being driven slightly faster than crank speed.
5. Replaced the SD1 header tank with an expansion tank from a Ford (Fiesta I think it was). The new tank is of the continuous bleed variety rather than the expansion only variety of the SD1 tank.
6. Replaced the thermostat with a 74C one and drilled three 3mm holes 120 degrees apart. One of the holes is at the top when fitted.
7. Fitted a hose connector into the highest part of the top hose witha bleed pipe which leads back to the expansion tank.
8. Fitted a lower temperature thermostatic fan switch. I think it is 87 to 92C now IIRC. It was something like 92/98 before.
9. Baffled around the radiator to prevent any cooling air bypassing the core.
10. Removed my front number plate which was causing a very slight impediment to airflow. I don't think it made any difference to be honest.
11. Cut out bonnet vents in the side of the bonnet to help vent hot air from engine bay.


So, as you can see, I've tried quite a lot of things and am still struggling to cool the engine. My next move will need to be either to try running it without a thermostat (or with a thermostat with centre removed) and if this doesn't work then either my water pump is not 100% efficient (got it on ebay) or my radiator is not up to the job.

However, I have some concerns that my bleed hose plumbing might not be perfect and would appreciate any comments. I am concerned that my bleed hoses might be diverting water away from the radiator and at idle speed this might be enough to prevent it staying cool. Should I try fitting a restrictor or is there a better way to set up my bleed pipes? Should some of them be blocked off once the engine is filled and bled (eg. the radiator bleed hose)?

I'm also worried about my top hose as it is less than ideal and runs downhill to the radiator. It is also higher than the water level in my expansion tank which can't be ideal but I need to leave some sir in the tank for expansion. Should I maybe reinstate my SD1 header tank as well as the expansion tank and connect the header tank to the radiator bleed hose. Then I can top the expansion tank right up and use the header tank to handle expansion due to heating.

I need a second opinion on this lot before I go out and buy a new radiator. The one I have should do the job as others have used it on more powerful cars. I know it's not that simple but I have a feeling that something else is working against me here,not just a marginal radiator.

Many thanks,
Craig.

[harvey]

I think you need to run a pipe from the bleed pipe in the centre of the manifold (between the carbs) to the highest point in the cooling system (which looks to be the plastic header tank on the bulkhead) rather than to the 3 or 4 seperate places that it seems to be going now. Make sure the metal pipe where it enters the manifold isn't blocked aswell.

[craig1410]

I think you need to run a pipe from the bleed pipe in the centre of the manifold (between the carbs) to the highest point in the cooling system (which looks to be the plastic header tank on the bulkhead) rather than to the 3 or 4 seperate places that it seems to be going now. Make sure the metal pipe where it enters the manifold isn't blocked aswell.

Hi, thanks for your comments.

I can confirm that this little vent pipe is not blocked as I have cleared it out on more than one occasion with a drill bit.

Yeah the bleed hose arrangement might be part (or all) of my problem. On the SD1 installation, do you know if it is this pipe which leads to the header tank or is the header tank connected to the radiator? I always thought it was connected to the radiator but then that makes me wonder where the little vent pipe was connected to...

I made some measurements tonight of the relative heights of various bleed pipes etc with reference to the seam across my expansion tank which is pretty much normal water level. I found the following (negative means below, positive means above header tank seam):

Radiator core (top edge): -98mm
Top of top hose where it connects to radiator: -110mm
Top face of rocker cover: -20mm
Radiator bleed pipe (top): -106mm
Inlet manifold small bleed pipe: +25mm
Top of inlet manifold: +38mm
Top rad hose highest point: +25mm

It is clear from this that my water level needs to rise above the seam in the header tank because I can't mount my header tank any higher without needing a bonnet bulge. The cap already touches the bonnet. If I raise the water level then it is likely to blow out water when hot due to insufficient air space above the water level.

With my old SD1 header tank I didn't have this problem because the header tank coolant level has no direct relationship with the engine coolant level, it just maintains an expansion space and allows air to escape as expansion takes place.

Should I try going back to the header tank fed from the inlet manifold small vent pipe and just bring the other bleed points together into a manual bleed screw? That's what I used to have before I made a number of other improvements to the engine and cooling system but I used to get water blown out of the header tank when hot.

Regards,
Craig.

[CastleMGBV8]

Craig,

I would agree with other comments that your current sydtem is too complicated and you only need one small feed from the radiator to the expansion tank and the bleed from the top of the manifold can also be teed in to go to the expansion tank as well.

The rover V8 is notoriously difficult to bleed all the air out of, and your top hose layout is not helping as it higher than the engine and the rad header tank.

I feel you really need to get that top hose down, the problem is you have the wrong thermostat cover outlet which points upwards and was meant for a vehicle with a much higher rad position.

You can get a thermostat housing outlet that has the pipe horizontal which would help enormously.

To prove the point you can blast the air out of the system by firstly getting the front of the car as high as possible, and with the expansion tank removed and placed well above engine height and with the cap off run the engine until the stat opens and then give some revs.

It will spurt some HOT water out so make sure nobodys going to get splashed repeat revving up a few times then turn off, top up expansion tank to half full, replace cap, and refit expansion tank as high as possible.

This will probably cure the problem but it may return if you do not address the the top hose height problem.

One other comment you mentioned that you have a smaller water pump pulley, it is not recommended to riun the pump at MORE than 1 to 1 as it will push the coolant through the rad too quickly and not be cooled.

Good luck,

Kevin.

[craig1410]

Hi Kevin,

Yes that was something which was bothering me too (top hose height). I think I may be able to do something about it now that I have re-curved my dizzy as I can remove the vacuum advance which will help provide space through which to bring my top hose. If I can get hold of a better thermostat outlet as you suggest then I can probably drop the top hose by 2 inches which will have a number of benefits for me including doing away with an ugly bonnet bulge...

My radiator top bleed pipe is only slightly higher than the radiator top hose so I'm thinking if I can get my top hose to flow directly from radiator to thermostat housing then I any air would flow into the thermostat housing and I can dispense with the radiator bleed hose as well. That should mean that all air would flow up into the inlet manifold pent roof and exit via the bleed hose to my header/expansion tank.

So action plan is to get a straight thermostat outlet (anyone know where I can source one?) and then construct a better top hose. Then rearrange my awful bleed hose setup to get down to one bleed point in the inlet manifold.

Thanks for your comments,
Craig.

[CastleMGBV8]

Craig,

Sorry meant to mention where you can get one, they are not made as OE but Dave Vale at V8 conversions Farnborough Kent has them cast specially with or without the bypass circuit depending on you set up.

Tel 01689 858716 he's only in on tues, thurs, fri, and saturday and their £25.00

Kevin.

Pic of layout in my MGBV8

[craig1410]

Craig,

Sorry meant to mention where you can get one, they are not made as OE but Dave Vale at V8 conversions Farnborough Kent has them cast specially with or without the bypass circuit depending on you set up.

Tel 01689 858716 he's only in on tues, thurs, fri, and saturday and their £25.00

Kevin.

Excellent, I'll give him a call on Tuesday then.
Thanks,
Craig.

[ChrisJC]

What have you done with the heater circuit?

Chris.

[craig1410]

What have you done with the heater circuit?

Chris.

Hi Chris,
I have blanked off the back of the inlet manifold and am using the other pipe which goes under the inlet manifold to connect my expansion tank outlet.

Cheers,
craig.

[ChrisJC]

Is there any kind of thermostat bypass, i.e. before the stat opens, can the water circulate?

Chris.

[craig1410]

Is there any kind of thermostat bypass, i.e. before the stat opens, can the water circulate?

Chris.

yes it has the standard SD1 bypass arrangement with a short hose between water pump housing and inlet manifold.

Craig.

[ChrisJC]

I've not quite got my head around exactly what you have, however I think you need to be clear about whether you have an expansion tank or a header tank.
The differences are as I understand it:
-Header tank is effectively in parallel with the radiator. It has to be high up, as it determines the water level in the system, and air has to be able to naturally find its way up into the header tank. The header tank is pressurised.
-Expansion tank has a single connection to the cooling system. It is not pressurised. You have a device at the highest point of the cooling system which allows overpressure to escape along a small pipe into the bottom of the expansion tank. With temperature cycling, air will be 'expanded' out into the expansion tank, where it will bubble away, and coolant will be drawn in when the engine cools. The expansion tank can go wherever you want it, it doesn't have to be high up.

Which system have you got?

Chris.

[craig1410]

I've not quite got my head around exactly what you have, however I think you need to be clear about whether you have an expansion tank or a header tank.
The differences are as I understand it:
-Header tank is effectively in parallel with the radiator. It has to be high up, as it determines the water level in the system, and air has to be able to naturally find its way up into the header tank. The header tank is pressurised.
-Expansion tank has a single connection to the cooling system. It is not pressurised. You have a device at the highest point of the cooling system which allows overpressure to escape along a small pipe into the bottom of the expansion tank. With temperature cycling, air will be 'expanded' out into the expansion tank, where it will bubble away, and coolant will be drawn in when the engine cools. The expansion tank can go wherever you want it, it doesn't have to be high up.

Which system have you got?

Chris.

Hi Chris,

Sorry to cause confusion, let me explain the SD1 standard setup (donor car) versus what I had in my kit car initially and what I have right now:

SD1 Setup: SD1 radiator with integral filling cap, top hose, bottom hose and two bleed hoses right beside each other. One goes to the little vent pipe in the middle of the inlet manifold and then other pipe goes to the header tank. This tank is a plastic tank of around 1.5 litres capacity with a single 8mm connection at the bottom of the tank and a 15psi bayonet type pressure cap with another 8mm connection at the top for coolant which has got past the pressure cap.

My initial setup: Polo radiator with single bleed pipe leading to t-piece where it joined the bleed pipe fitted to my top hose at the highest point. The third leg of the t-piece just had a screw fitted so that I could expel air and then seal up the screw. I used the SD1 pressurised header tank as per the SD1 setup but I connected it to the little vent pipe on the inlet manifold as this is the highest point on my setup due to the radiator being much lower than in the SD1 setup. With this configuration I was getting water blown out of the header tank overflow pipe onto the ground.

Current setup: Polo radiator with single bleed pipe leading to a pair of t-pieces arranged like a letter "H" (ie. four connections). The other three connections go to the radiator top hose bleed point, the inlet manifold vent pipe and the new header tank. This new header tank is also pressurised with a 15psi plastic screw cap but this tank has a large (approx 19mm) connection at the bottom and a small (10mm) connection at the top. I have connected the large pipe to the 19mm pipe which runs under my inlet manifold which in turn connects via a short hose to the water pump intake. When idling I cannot see much coolant running into the header tank via the 10mm top connection but when I rev the engine I can clearly see it. I don't seem to lose coolant with this configuration but I'm still having cooling issues when stationary or at medium speeds (50MPH). I do think I need a better cooling fan to keep it cool when stationary but at 50MPH the fan would have no effect so I obviously have some other issue.


I hope that helps to clarify my setup but please kick me if you need any further details or clarification.

Cheers,
Craig.

[ChrisJC]

Hmm, well, I think it must be the size of the radiator.

Is there any way to measure the temperature of the bottom hose whilst driving along? That would prove it.

Or temporarily strap on a huge radiator.

I just think a Polo rad will be woefully inadequate.

Chris.

[ian.stewart]

im of the same thoughts, polo rad does sound as if it would be too small, I have a sirrocco[sp] rad on the wall of my garage, and thats where it has been for the last 10 years, as I have no intention of using it on my v8 because I think its too small.
How is the air directed to the rad, air is like water, meaning it will take the route of least resistance, when ever I build a car, I ensure the air is directed to the rad, and the rad is sealed so no air within reason can get past, and must flow thru the rad, a free standing rad will allways work less efficently than a fully ducted rad, there be a free route for air to escape from under the bonnet,