MGB V8 EFI Cooling Problem

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madmal007
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MGB V8 EFI Cooling Problem

Post by madmal007 »

Hi all,

Just finished converting my MGB v8 Roadster from flapper EFI to MegaSquirt and had the car Dyno tested at 228bhp. That's the good news....
However, I'm finding that the cooling system is struggling to cope and the temperature gauge is just under the red at tick over. Both fans just about hold it there and on the move, the gauge drops a fraction but nowhere near the center of the gauge. The MS sensor is also showing borderline temps.

I've fitted a new water pump and 82 degree stat, the rad pipes are not hard and there is no sign of oil in the water or water in the oil. Compression is all good.

The build invoices show a MGB v8 rad purchased years ago and rather cheap at £90 so I'm suspecting the rad is past its best. I have flushed it and the car several times and no sign of rust.

The car does not boil over and the expansion tank fills as it get hot then vents back to the system as it cools.

Grateful for any observations and any recommendation's for a high performance rad. Rimmer's and SC Parts all want £500 plus for an Alloy rad.

Thanks



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ChrisJC
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Re: MGB V8 EFI Cooling Problem

Post by ChrisJC »

Are the fans moving the air in the correct direction?

Chris.
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stevieturbo
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Re: MGB V8 EFI Cooling Problem

Post by stevieturbo »

Something does not add up

Is it actually overheating ? What temperature is it getting to ?

Is water flowing through the rad ? ie, top/bottom hoses actually warm ?

You say the hoses do not get hard, that should be nigh on impossible on an overheating engine with a sealed cooling system. Pressure is normal...excess pressure is not, but both would see "hard" hoses.
Get a pressure gauge attached to the system to see what's happening.

Are you sure the overall layout of the system is correct ? Draw a schematic.

And of course....has it ever worked correctly in its current configuration ?
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Ian Anderson
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Re: MGB V8 EFI Cooling Problem

Post by Ian Anderson »

One problem that occurs is that the flow of coolant heads around the cabin heater route and bypasses the main radiator.

Water will take the line of least resistance so clamp off one of those pipes with a mole grip and see if the temp drops as then the water should be forced through the radiator.

Ian
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Re: MGB V8 EFI Cooling Problem

Post by DaveEFI »

If it was once OK, chances are your rad is partially blocked. Flushing won't remove the crud, you'll need chemical assistance. Not too keen on adding a cleaner to the coolant on an ally engine, so I'd do the rad on its own. May be easier to remove it.

I had success with the blocked heater matrix on my SD1 using citric acid bought from Ebay. I didn't remove it, but plumbed in squeezy bottles to the in and out and filled it with the acid. The squeezy bottles allowed it to be 'pumped' back and fore. With the rad out you could block the outlets after filling with the acid, and just invert it a few times. A hot air gun or fan heater on the rad should speed up the process.
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madmal007
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Re: MGB V8 EFI Cooling Problem

Post by madmal007 »

Thanks for the responses, much appreciated.

The fans are are both sucking from the grill, through the rad and into the engine bay. One fan is controlled by the MegaSquirt, the other is manual switch on the dash.

Hopefully the sketch and pic might help explain the current set up.

It's not overheating but running on the limit, both rad hoses are hot. Hoses are hard when running but soften on cool down so not liner issue?

Tried turning off the heater but no improvement. Would clamping the hose be any different?

Bottom line is, I don't know if it ever worked properly. The cars done about 800 miles since the re-shell/conversion but may have only covered short trips as the old flapper EFI was massively over fueling.

Not sure why it has two rad caps??

Mal
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Re: MGB V8 EFI Cooling Problem

Post by DaveEFI »

Interesting, you have the federal EFI. I've just done a Megasquirt conversion for a US SD1 with that injection. Built the MS into the Lucas case, as the owner reckons the 'MOT' in CA is very strict about obvious mods. It was tuned by a remote tuner in the UK, and I'm told after a number of teething problems is now running better than it ever did with the flapper injection.

Incidently, a flapper running very rich is most likely a problem with the CTS or wiring to it.
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Re: MGB V8 EFI Cooling Problem

Post by madmal007 »

It's actually a Vitesse plenum that's had a section cut out and rewelded. The inlet trumpets were also shortened to suit. I gave it a clean up and respray while it was off the car.

If you look closely, you can see the TPS bracket that I made from the drawing you supplied me a while ago. Thanks again for that.

Just need to get this dam cooling system sorted....

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Re: MGB V8 EFI Cooling Problem

Post by richardpope50 »

Elsewhere on the forum is my epic struggle to sort out my cooling problem that was finally solved a couple of years ago. First I had a blocked rad despite umpteen flushes - gunge in the vertical pipework. Second, I converted the rad to two way. So simple to do and makes it so much more efficient. basically weld in a header tank baffle half way to stop the flow from one side to another. Then move the usual bottom outlet to a top outlet.

This forces the water down one side and up the other whereas normally it travels across the top to the other side and straight down to the outlet. The fans here will only cool the area on the right as the water on the left simply stays where it is. It makes a huge difference to the cooling capabiliy of a rad.

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Re: MGB V8 EFI Cooling Problem

Post by ChrisJC »

There is nothing obviously wrong with that setup.

You could borrow an Infra-red camera and look at the rad to ensure it's hot all over.

Otherwise maybe it is just not a good enough heat exchanger and you need a custom read made as thick as possible.

In my Landie, I have a rad which is about 600 x 550mm, and it's perfectly adequate for a tuned 4.6l enging pushing along a Land Rover. Temps are rock steady.

I had it made by Pro-alloy motorsport; it's very good.

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Re: MGB V8 EFI Cooling Problem

Post by richardpope50 »

I got mine made by https://custommaderads.co.uk/?gclid=EAI ... gLVXfD_BwE
Really competitive and very well made. darren is his name - Nottingham.
Richard.
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madmal007
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Re: MGB V8 EFI Cooling Problem

Post by madmal007 »

Thanks all for the feedback.

I also feel the radiator is the weak link and have decided on Serck Motorsport as I can get one on next day delivery. It seems that not many suppliers have MGB V8 rads in stock although I guess they are hardly high demand items.

Fingers crossed for a test drive on Sunday in 29 degree heat (allegedly)!

Mal

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Re: MGB V8 EFI Cooling Problem

Post by DEVONMAN »

Looking at your layout, I suggest that you put a plain full seal cap at the top hose and not a pressure type. This will allow coolant and any air to flow up to the header tank from the onset of temperature rise.
Just to add, I've heard that MGBs run cooler in the summer when the heater is off because hot uncooled coolant is not then flowing back into the block and bypassing the rad.
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Re: MGB V8 EFI Cooling Problem

Post by SuperV8 »

madmal007 wrote:
Wed Jun 09, 2021 12:06 pm
Thanks for the responses, much appreciated.

The fans are are both sucking from the grill, through the rad and into the engine bay. One fan is controlled by the MegaSquirt, the other is manual switch on the dash.

Hopefully the sketch and pic might help explain the current set up.

It's not overheating but running on the limit, both rad hoses are hot. Hoses are hard when running but soften on cool down so not liner issue?

Tried turning off the heater but no improvement. Would clamping the hose be any different?

Bottom line is, I don't know if it ever worked properly. The cars done about 800 miles since the re-shell/conversion but may have only covered short trips as the old flapper EFI was massively over fueling.

Not sure why it has two rad caps??

Mal
Looks strange to me;

You have the small pipe on the right of the inlet manifold going to the coolant pump inlet.
This is normally fed to the high point on your cooling system to bleed any air out of the cooling system, this is acting like your thermostat bypass circuit, but any air in the system will just get circulated back into the pump inlet.

Also what type of rad cap do you have in the top hose?
From the way you have drawn it looks like you have designed an overflow type system, which needs a certain type of cap in the top hose (with a double seal). Once the coolant reaches the cap rated pressure the fluid expands into the BOTTOM of the catch tank. When it cools it sucks in this coolant back into the system.
Your tank looks like it has the inlet port at the top? does this have a dip tube internally to the bottom of the tank?

Can you share more photos of the tank arrangement? and pressure caps?

Tom.
Dax Rush 4.6 supercharged V8 MSII

madmal007
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Re: MGB V8 EFI Cooling Problem

Post by madmal007 »

The small pipe from the pump is the supply to the pre heater on the plenum chamber, the return from the pre heater used to go to the small inlet connector on the manifold. I have bypassed the pre heater so connected the pipe from the pump straight to the manifold.

The radiator caps are all standard.

The expansion tank has a bottom connector that goes to the top hose but its not so easy to see from the pics. The top connector on the expansion tank is the overflow.

I've fitted a new alloy rad, which was larger than the rad I removed, so I'm now not even sure that the existing rad was the correct one. Either way, it has improved the cooling. I've also relocated the front number plate as it was completely blocking the air flow to the bottom section of the rad and the oil cooler. I've also rewired the fans so the MegaSquirt controls both fans rather than just one.

Hope to get out today for a test run.......

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