Coolant circuit 3.5 Efi

I have a Q about coolant circuit on a 90 with a 3.5 V8 Efi non-serpentine + RRC ZF autobox conversion.

Since the conversion the rad needs regular toping up as it goes down a couple of inches over time and the expansion tank seems to fill up more than it should.

There is no over pressurisation, no fumes or bubbles in the coolant, oil clean no emulsion, exhaust not steamy, no running problems and no obvious leaks.

The expansion tank (original from the 2.5P) has a small feed from the top of the rad, an overflow tube and a large bore pipe from the bottom which I think originally joined the rad outlet hose to the water pump, but is blanked off.

With the large bottom outlet closed, on cooling the water should return via the small pipe to the rad top...but it couldn't as the outlet was above the water line?! So I fed some clear fish tank tubing through to the bottom of the expansion tank, the other end into the outlet tube which was reconnected to the nipple. The inner tube fitted nice and snug. Filled the rad and plenum tower, checked the expansion tank and ran it to thermostat opening, monitored this by touch and an eye on the VDO temp gauge (~88*C). Checked levels and went for a drive. On return, let it cool a bit, carefully released the expansion tank lid with just a 'pssst', no eruption of scalding coolant, burping or gurgling. Started to remove the rad filler but water seeped out almost immediately, ditto the plenum filler tube. Checked again once cool and coolant fills the rad properly and expansion tank is at the right level and not overfull. Runs at ~85-90.

My Q is whether this set up is correct and adequate or should I get the bottom hose with the tail to the expansion tank (??? NTC7297 and NTC5632). I think it was done this way as the bottom hose has an XEng thermoswitch for the electric fan plumbed in although there's room for a T.

Any thoughts most appreciated.

P.S. I have an 11-blade viscous fan and V8 shroud which after modification I intend to replace the Kenlow electric. It's only a single 12" and I don't think it's enough. Plus I hate the switching on and off so the ali engine cycles hot and cool. I prefer the consistency of a viscous (not looking to open a debate on this one!)

Are there any V8 gurus available today?!

Further to the above I think I need either one of these bottom hoses with the expansion tank tube (NTC7297 or NTC5632).

Water from the rad leaves via the small hose on top of the rad, enters the expansion tank and returns to the water pump via the bottom outlet hose.
On my current set up the water returns to the rad by suction via the small expansion tank feed on top; the connection (orange) to the water pump via the rad outlet is missing.

It seems to work OK but is it the correct method? I don't want to damage my V8 by poor coolant circulation.
Cheers.

Sounds like a bit of a missmash of parts.
The early RRC 3.5Efi - mine, 1986 - is much the same as your diagram but:
Only one small hose goes from the rad (your 'expansion tank feed') to the inlet pipe of the expansion tank. Internally this tank has a pipe that goes to its bottom so it's both the feed AND suction return.
There is no other small hose - 'to heater' from the top of the rad.
The bottom hose - 'outlet to water pump' - does not have any branches.
The heater hoses are one taken from the inlet manifold and the other from the stub at the rear of the engine front cover. You have the tower filler (ERR319 ?) & the RRC hoses are shown here: http://new.lrcat.com/#!/1230/73417/75066/6025 Item 7, 8 & 9.

Following pics are of mine. Has what are referred to as 'internal' inlet manifold water pipes. Yours sounds like the 'external' type
Pic below is bottom hose to water pump
Below are the two hoses from the rear of the engine front cover which do the inlet manifold & heater
Below the patterned hose is the top hose from stat housing to rad
Below hose from rad to expansion tank (disregard the one on the right, rads with just the one for mine were NLA so it's just blanked off with a bolt in the end) The overflow stub is just visible below the cap at 5 o'clock, must put a hose on it!

HTH

ETA. I really MUST get around to fitting a +ve feed bus bar!

I'm not a V8 guru, but I DO have a factory V8. Using your dia above... where your orange connection should be I have a medium sized pipe that goes down and forms part of a T with the hose that runs from the bottom of the rad to the water pump - which look v similar to the photos you've fished out above, yes. In the middle pic you can just about make out the T in the middle, way below the pulley

@Ratae @romanrob
Thanks for your input.

Ratae said:

Internally this tank has a pipe that goes to its bottom so it's both the feed AND suction return.

Click to expand...

That was missing hence the coolant loss in the rad and the build upon the expansion tank. Now I've fitted a tube to the bottom of the expansion tank the rad stays full and the expansion tank halfway, so it is both feed and suction return.

So, do I also need the thicker expansion tank downpipe to the bottom rad hose leading back to the water pump or is it ok as it is? Could use NTC7297 or NTC5632 as in my first post or put a T in the bottom hose and connect it to the expansion tank outlet. Or just leave it alone; as I say no running or cooling issues observed.

Cheers

You could probably remove your tube & use one of the hoses you mention to attach to the bottom of your expansion tank - later RRC did & I presume they did it for a reason - and see what happens.

Ratae said:

You could probably remove your tube & use one of the hoses you mention to attach to the bottom of your expansion tank - later RRC did & I presume they did it for a reason - and see what happens.

Click to expand...

I'll see how she runs now as is and might try that later and compare.
The engine is from a 1992 Discovery 1, 3.5 non-serpentine, hot-wire AFM but pretty much the same as the RRC.
I guess the big exit pipe ensures the coolant is directed back to the pump faster than syphoning back from the header tank into the rad?
As long as the temp and coolant levels are normal it is ok.
Thanks.

Found this thread on V8 forum https://www.v8forum.co.uk/forum/viewtopic.php?f=9&t=15285
Header tank into bottom hose

• Quote
  Post by Twinturbotr7 » Mon Mar 11, 2019 10:27 pm
  
  Hi when I read other posts on here most people say the best thing is to put the bigger connection at bottom of the header tank and tee it into the bottom hose why is this the best idea ? Surely any hot coolant that will be in the header tanks will go straight back into the engine, if it went back into the rad even halfway down it would help cool it down before being sucked into the engine ?

The general consensus was that the header tank allows for coolant expansion and to collect air as the high point of the cooling system - there should be no significant coolant flow through it. But it could get blocked or as in my case the internal syphon tube in the expansion tank missing, leading to loss of coolant in the rad.

Still doesn't explain the header tank to bottom hose set up.

Edited to add: is the big hose from the bottom of the expansion tank for adding coolant without opening the rad? I fill the rad and block thought the top screw plug in the rad, through the rad and out of the bottom hose. Adding to the expansion tank itself on mine won't top up the rad or the block?

They can sometimes be a bit of a pig to bleed - which is why I think the topping up tower on the later ones came into being.

Don't forget the stat must be mounted with the jiggle pin at 12 o'clock or air will just get trapped behind it & if hot water can't get to it it won't open.
FWIW I always remove the jiggle pin so it's just an open hole & I've not had an issue.
I don't have the tower type filler & the expansion tank only has the one pipe so adding to the expansion tank only tops that up, not the rad.
Your current set-up is pretty much the same.
I fill through the screw plug until the rad is almost full then start & allow to idle, topping up as necessary until the rad is completely filled. (Cap is off the expansion tank throughout) Refit plug. Fill expansion tank to the 'WATER LEVEL' plate which mine has inside it. Fit cap. Run up to normal temp then allow to cool & top up if required.
I find with mine that squeezing the bottom hose with the expansion tank cap off but the rad screw plug fully done up can help burp the system by pushing air out via the expansion tank. Releasing the hose draws coolant back from the expansion tank.
Below is the factory instruction for mine, shows the level plate in the tank:

If you go for the branched bottom hose fitted to the expansion tank bottom pipe (currently blocked on yours) then you would need to remove the plastic extension tube you've fitted in the tank.
Water will be able to flow into the bottom hose via the tank & I don't know what differences there may be in the filling procedure & my RRC wsm doesn't cover that.
There were a number of different tanks & hoses used over the life of the RRC & mine was the early metal tank 3.5Efi one. I can only assume the subsequent set ups were to address issues.

Thank you.

Yes, I have the plenum tower for filling and now with the expansion tank syphon tube all seems to be working ok and the rad stays full, so little need to add the branched bottom return hose. 82deg stat with jiggle pin at 12o/c. Bleeds easily now as it's no longer sucking in air from the expansion tank. The temp is much steadier as there is the full complement of coolant in the rad.

My mistake in that the second 8mm hose from the top of the rad goes to the throttle body, not the heater.
The steel pipe which curves rearwards to the bulkhead with the filler tube goes to the heater and then flows via another steel pipe back, down the front of the engine to the thick rubber pipe from the radiator to the water pump intake.

I feel happier now

Ratae said:

They can sometimes be a bit of a pig to bleed - which is why I think the topping up tower on the later ones came into being.
There were a number of different tanks & hoses used over the life of the RRC & mine was the early metal tank 3.5Efi one. I can only assume the subsequent set ups were to address issues.

Click to expand...

My '87 (code DA) has the exact same set-up as yours & I need to replace the rad. after the holiday
Would the twin outlets on these generic radiators exist to cater for the older carburettor fed V8 ?

norseman said:

My '87 (code DA) has the exact same set-up as yours & I need to replace the rad. after the holiday
Would the twin outlets on these generic radiators exist to cater for the older carburettor fed V8 ?

Click to expand...

If you look at the bottom pic of my post which shows the expansion tank you can see there are two small hoses which run from the top of the radiator. The ones with a bit of brown tape round them.
I've put the top one onto the expansion tank inlet & the one from the bottom has a bolt in it (not a set screw) and a hose clamp. The bottom one has the end with the bolt in pointing towards the red keyed isolator.
Was just the simplest way of blocking it off when I did it.
When I fitted that rad as a replacement years ago that was the closest that was available. I don't know where that hose would usually go. Had it re-cored a couple of years ago & the end tanks are reused.
This is one of the reasons why I suggested getting yours re-cored in your other post.

norseman said:

My '87 (code DA) has the exact same set-up as yours & I need to replace the rad. after the holiday
Would the twin outlets on these generic radiators exist to cater for the older carburettor fed V8 ?

Click to expand...

No, for the 3.5RR efi it needs one, (or both) blanking off, must look in my RR parts book to for a drawing as its a long time ago of owning a RR

This twin outlet rad is for the later 3.9 similar to that fitted to my disco, and the supplier does mention the blanking if used on early models.
Attached a photo which shows both the disco rad outlet/pipes (side by side on a genuine rad), one goes to the the throttle side of the plenum the other enters the expansion tank from below, next to another similar pipe thats a T off the bottom hose.
The later cooling system is close circuit hence the expansion tank has a a screw cap fitted with to valves, the system has no overflow pipe, unlike the 3.5 that has an overflow from its metal expansion tank filled which your RR should have, or did when it left the factory. As mine had

discool said:

No, for the 3.5RR efi it needs one, (or both) blanking off, must look in my RR parts book to for a drawing as its a long time ago of owning a RR

This twin outlet rad is for the later 3.9 similar to that fitted to my disco, and the supplier does mention the blanking if used on early models.
Attached a photo which shows both the disco rad outlet/pipes (side by side on a genuine rad), one goes to the the throttle side of the plenum the other enters the expansion tank from below, next to another similar pipe thats a T off the bottom hose.
The later cooling system is close circuit hence the expansion tank has a a screw cap fitted with to valves, the system has no overflow pipe, unlike the 3.5 that has an overflow from its metal expansion tank filled which your RR should have, or did when it left the factory. As mine had

Click to expand...

Many thanks for that info. seems I'd got it the wrong way around
Viewing your attach. I now recall the plastic exp. tank from my ownership of a '93 Vogue. After two years it slipped a liner & I've stuck to 3.5's ever since.
nb. Congrats. on such a clean engine bay !

Parts catalogue pages showing the radiator & expansion tank + hoses fitted to the EFI 3.5 & 3.9 up to 1991, thats as far as my parts catalogue goes up to.

Pic #5 is the 3.9 expansion tank same for the later D1.

norseman said:

Many thanks for that info. seems I'd got it the wrong way around
Viewing your attach. I now recall the plastic exp. tank from my ownership of a '93 Vogue. After two years it slipped a liner & I've stuck to 3.5's ever since.
nb. Congrats. on such a clean engine bay !

Click to expand...

Picture taken around 12 years ago but much the same now, but with a newer sealed battery fitted.

discool said:

Parts catalogue pages showing the radiator & expansion tank + hoses fitted to the EFI 3.5 & 3.9 up to 1991, thats as far as my parts catalogue goes up to.
Pic #5 is the 3.9 expansion tank same for the later D1.

Click to expand...

My system is that shown in TS6552, but I do not have any extension (or T off) from the bottom hose.
At the end of the day whatever I currently have works, with no problems in the hottest of weather, so I'll tell the garage to replicate once I've got the new rad. next month.
All your replies are appreciated, thanks guys. Happy New Year to all on here