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Advice on Cooling system V8


tommobot
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I'm after some advice on my cooling system for my hybrid.

I brought it with a defender front panel (and rad) and have been refiting the series III front panel along with a series II / III radiator.

I've read reports of people using this radiator with the V8 and it being ok.

My main question revolves around the header tank setup, as seen on the photo below I still have the original header tank, and the series III radiator has a header build in at the top I believe.

I've brought a non-pressure release cap, that I was going to put onto the rad and was aiming to keep the original header tank.

IMG_20160305_171825152_zpsxvr3usrh.jpg

Is this sensible, any other ways of doing it, any input welcome..

I'm aware that I could remove the header tank entirely, but I would imagine it would be difficult to judge the coolant level in the system without the header tank?

Anyways, input welcome.

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I think it'll run hot and most of time. Not saying you can't get it usable, but suspect it'll want an electric fan running almost all the time. If you do long distance green laning in low range expect it to boil up.

There will always be people who tell you theirs is ok, and maybe it is. But maybe they just don't realise how hot it's running, or their use is limited enough for it not to be a real concern.

Factory V8 90's have a MASSIVE rad on them. But they still run hot and when the rad gets old and clogged they'll overheat for certain use.

I have a large rad on my TR7 V8, probably twice the size of a series rad. I had the rad rebuilt and added an extra core too it. Now it's much better. But still likes a lot of airflow over it.

As for the header tank, I'd go with a V8 style header tank/expansion bottle and pressure gap personally. I suspect the old Series setup is going to be a compromise.

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I've fitted a fan infront of the rad, theres space behind still just about to squeeze another one in...

I thought it may run hotter, however I don't use it for heavy off-roading at all so it should be ok in that regard.

My aim was to run it for a few months and see how it goes, if its not working / too hot, I would get the existing rad re-cored.

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I ran a 3.9 with a Series rad & standard expansion tank (non-pressure type) with no issues. You'll need an electric fan, I used a Mondeo one. Never gave me any problems or overheating, including off-roading, green laning, and towing.

If you rad's in poor condition then it's advisable to fit a decent new one but that's just common sense.

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Why not just keep the standard SIII rad and plastic side expansion tank, since the bracketry will all fit without work and the system is well proven?

I would be up for doing that, as you say its a proven system..

However, I'm getting slightly confused with the plumbing of all this..

Below is standard setup I believe, the small pipe below the filler cap leads directly to the expansion tap?

expansion_bottle-41.jpg

On the previous setup my engine / rad had flow from the top of the intake manifold to an inlet on the top of the radiator, I can't see where this would now flow if I used the above setup.. :blink:

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It's an expansion bottle, nothing more, so allows the water from the rad to expand into the tank, then be syphoned back into the rad as the system cools down after use. The hose from the rad neck goes to the bottle port that extends down tot he base, the other bottle port on the flat of the bottle (nearest the cap) runs down the bracket and ends, dumping coolant that overfills the bottle overboard. I found in practice that when cool, the bottle was about half full, and would be completely full when hot (you fill the rad and engine system and the bottle to the top, and the system will self level after the first run up - you just need to keep an eye on the bottle level for the first few runs as trapped air is expelled through the bottle, syphoning water back in on cool down, self purging the system, which could cause the tank water level to drop too low when cool, needing a top up).

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That little connection on the manifold between the carbs is the manifold air bleed. You want it plumbed into somewhere it won't let air get sucked back in. I'm running a custom radiator on my S3 V8 and have that little hose running into a connection on the bottom of the Disco expansion tank I'm using. Tough call where to attach it on yours! I'm wondering if you'd get away with teeing it into the hose between the radiator and series expansion tank, but I'm not 100% sure that'll work.

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It would need to go into the sealed cooling system for my money.

I'd suggest perhaps one of the heater pipes via a small t-piece? :)

Or you could get an extra small port brazed into the series rad -probably cost all of £10 at a radiator place.

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The plenum pipe needs to go into the top tank of the radiator ,or you could get a t piece into the top rad hose , the pipe on the side of the rad cap neck needs to go to an expansion tank or bottle . The rad cap needs to be the correct sort for use with expansion tank , eg will have a little valve flap on the bottom that is designed to relief vacuum when the rad cools .

If you find that you are running a bit hot then a good help is fitting a decent sized oil cooler in front of the rad .

I built a 88 back in late 70's with RV8 and used a shortened series rad mounted up on the front cross member to retain the series front ,and the oil cooler and rad worked well .

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I like the idea of the blank cap on the rad and the pressure cap on the rangy expansion bottle as it keeps the top hose and rad full to the top all the time.

I ran my plenum line to the rangy expansion bottle. The old Ford Transit is the same.

The Craig Davis electric pump we put on my RV8 was so successful at the last event it suggests a lot of the problems are from the standard water pump which can't handle anything but a rad in good condition.

Not all copper rads were 100% solder dipped, so they drop performance as they get old and corrosion separates the fins from the tubes.

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Blank cap and brass RRC expansion tank was what I fitted to my 3.5 in a 88".

Oh and a bog standard series 3 radiator too ?

This must have been the coolest running V8 I've ever known. The 16" electric fan only ever ran occasionally in traffic on a hot day, or a little more frequently when off roading.

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Thanks for the replies guys! Lots of good information flying about :)

So, the 'easiest' solution, with what i've got at the moment I guess would be something like this:

cooling_zpsrqed9lpe.jpg

Blue - hose from carbs to top hose or heater hose

Yellow - Rad to header tank

Red - Blanking cap on radiator

This would mean i'd only need a T junction on the lower hose, alternatively as suggest I could add it into to 1 of the hoses going to the heater unit, with the addition of a 1 way valve... thinking about it, that actually sounds easier?

So, does this all sound feasable, sounds ok in my head, input welcome..

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There are some photos of the radiator I have on my 3.5 Series here

I don't have any issues with temperature unless I forget to turn the 'wading' switch off. :blush:

The overflow tank is the same as the one posted by tommobot

Where did you locate the flow from the carbs, the blue one on my photo... I assume thats the new one you've located at the top of the radiator?

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That goes into the bent pipe that comes out of the top of the radiator.

I can't take any credit for this, as it is all as built before I bought it.

The only things I have done to the cooling is to add a Kenlow sensor and relocate the overflow bottle to a bracket mounted on the NSF chassis rail (along with the coil).

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That all makes sense to me, the only question, in my mind at least is where to run the pipe from just below the carbs..

As shown on image below, that used to go into base of radiator... :unsure:

DSC04336.jpg

Hey! That's my engine! Or that's what it used to look like anyway. It's injected now and has been for some time...

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Thanks for the replies guys! Lots of good information flying about :)

So, the 'easiest' solution, with what i've got at the moment I guess would be something like this:

cooling_zpsrqed9lpe.jpg

Blue - hose from carbs to top hose or heater hose This pipe needs to go to t piece on top hose or to t piece on yellow pipe that attaches to spigot on rad cap socket

Yellow - Rad to header tank ok as long as header is above rad

Red - Blanking cap on radiator

This would mean i'd only need a T junction on the lower hose, alternatively as suggest I could add it into to 1 of the hoses going to the heater unit, with the addition of a 1 way valve.What for ?.. thinking about it, that actually sounds easier?

So, does this all sound feasable, sounds ok in my head, input welcome..

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  • 4 weeks later...

So bit of a bump...

I got all the plumbing set up as the images above, with the non pressure cap etc.. and basically overheated again... temperatures rose, stationary or moving.

So, plan number 2; I removed the header tank, and ran it as the Series 3 set up with the outlet between the carb tee'd into the top hose as on the images below, again temperature rose, stationary or moving..

I'm thinking now, get rad recored- fit a viscus fan, and hope that this sorts it... The only solution I can think to possibly try a 300ti rad, but again this involves ripping it all apart again/ :angry2:

Other thoughts are that from memory, when I had the defender front end, it had a full width rad with 2 possilby 12 / 14 inch fans, if these fans weren't working it would again, overheat... So I'm wondering possibly i'm not shifting enough air through the rad

Thoughts / input again welcome..

IMG_20160420_190228054_zpsacjfblnw.jpg

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