Bypass Aux radiator 6 years on

[gmac78]

Alright lads,

When i first bought my S2 6 years ago one of the first jobs i did was to remove the Aux radiator and simply join up the two hoses. Now then, i have never thought anymore about it until i read last night that this should not be done as it will kill the engine prematurely I think the car was on a 132k when i bought it, now on 146k. Not much miles in 6 years, but to fair it has spent most the time off the road with other toys occupying my time.

With the engine rebuild now following RS2 spec upgrade, and a lot more time and effort gone in to it i will certainly be blocking flow through the two hoses, either fitting bungs to both hoses or just linking them together with a stopper of some sorts.

If i had read this at the time i would not have simply bypassed them, however i've never had any issues with it running hot etc so in my experience it seems to run fine bypassed.

Has anyone bypassed and actually damaged the engine living within the UK climate? Or even in hotter climates for that matter?

Cheers

[Rikki Kitto]

I think it is now accepted that these cars run fine without it, an all ally larger main rad from the likes of Vidar Skothiem might be a good upgrade when the original main rad gives up

[Error404]

It won't bypass the rad completely, but it will not force all of the flow through it, so it will be operating very inefficiently. Not problem maybe for a modestly driven road car in a cool climate. Once you start to put more load on the engine it will generate a lot more heat and you'll quickly run into problems. Just bung the ends rather than joining then. Or for a tidier job run the 10v rad & bottom hose without the aux rad provision.

[rynaqui]

I run the aux rad in Malta, pretty much everything is new - all sensors, radiators, oil cooler, hoses, thermostat and water pump. Never have a problem even in 30 degree + weather in traffic, never goes past 90 and 1-2 points. I would say that the system was operating much less efficiently when the radiators were the previous old ones. Everything nice and fresh made a world of difference for me.

[Jamin]

22mm Yorkshire stop ends fit perfectly into the hose.

[montyrs2]

I think it is now accepted that these cars run fine without it, an all ally larger main rad from the likes of Vidar Skothiem might be a good upgrade when the original main rad gives up

Ordered one from him and fitted. Cracking big rad, dwarfs the OE spec item. Very quick delivery and good quality part.

[macspring]

When I took out my S2 Avant auxiliary radiator I noticed the fan cut in more often in traffic. No adverse issues though.

If you're leaving it out, do use two respective stoppers as mentioned rather than just join the redundant pipes.

[gmac78]

Thanks for quick reply guys, good to hear that there seems to be no ill effect from running the aux radiator bypassed. However, since i understand that part of the system more now, i agree that it is not ideal to run it like this with the engine under even more strain from the RS2 spec.

I guess i won't be driving it flat out everywhere, just the odd burst here and there but i'll get some bungs made up offshore for peace off mind. Heading away tomorrow for two weeks and when i come back the car will be heading straight for an MOT. The time has finally come to get some proper use out of it. Exciting times!!

[steve briance]

I don't want to undermine the comments already made but i am not sure i understand why taking the aux rad' out and joining the ends of the two hoses will make any difference other than it removes the cooling effect of the mini rad'.

As far as water is concerned, i bet it doesn't know it is flowing through a matrix or a simple pipe - it is just being pumped through 'something', it is just one thing cools more than the other. Wouldn't it be the missing cooling effect of the aux rad that shows up any inadequacies in the main rad' rather than it bypassing it?


Unless having your Aux rad gets in the way of fitting something else you need under the bonnet, i'd opt for having one. I have just had a re-core done for a very reasonable £80 and its as good as new now and so are my coolant temperatures. If you are upgrading power output and want to make sure the cooling is up to scratch, i'd highly recommend checking the inside of the metal pipe where it meets the thermostat housing... I have recently rebuilt my engine and was amazed at how much gunk/rust/sludge had built up there. I'd say there was probably only 1/3 of the pipe left open to let water through . how it got like that i don't know but it will help not being there that is for sure!

[Rikki Kitto]

There are quite a few high power S2,s running with upgraded main rads, I opted to keep mine but when it gives up I will delete it it makes for better air flow to the front end and easier access for certain jobs. I think it just comes down to personal choice now as long as the main rad is upgraded to all ally maybe thicker core sure it will be fine

[macspring]

I should have added to my earlier post that I only left mine out because I couldn't find it in the garage when the car was being put back together. :roll eyes:

If you have one and it is serviceable, I don't recall that it is much easier to leave it off for day to day use / or that it makes running repairs that much easier ?

Correct me if I'm wrong though.

[Rikki Kitto]

No idea just guessing to be honest Less parts to service less restrictions at front end, at £300 last time I saw one advertised and around £180 cheapest one I've seen mine won't be getting replaced when it dies

[Error404]

I don't want to undermine the comments already made but i am not sure i understand why taking the aux rad' out and joining the ends of the two hoses will make any difference other than it removes the cooling effect of the mini rad'.

As far as water is concerned, i bet it doesn't know it is flowing through a matrix or a simple pipe - it is just being pumped through 'something', it is just one thing cools more than the other. Wouldn't it be the missing cooling effect of the aux rad that shows up any inadequacies in the main rad' rather than it bypassing it?

If you look at the hose layout, joining the two aux rad hose feeds up gives the coolant flow a direct route through the top of the rad end tank and straight back into the return to the thermostat housing. Even if 25% of the flow takes this route rather than going through the rad matrix, it's a significant reduction in efficiency. In reality its probably more like 40-50%.

[Bowie69]

I know it isn't ideal, but unknowingly I ran mine with a nicely bent piece of copper 22mm pipe joining the two hoses, 50K later there were no issues, but I have reinstated the aux rad now

Not saying do it of course, but I wouldn't worry too much...

[andy10v]

I don't want to undermine the comments already made but i am not sure i understand why taking the aux rad' out and joining the ends of the two hoses will make any difference other than it removes the cooling effect of the mini rad'.

As far as water is concerned, i bet it doesn't know it is flowing through a matrix or a simple pipe - it is just being pumped through 'something', it is just one thing cools more than the other. Wouldn't it be the missing cooling effect of the aux rad that shows up any inadequacies in the main rad' rather than it bypassing it?

The water will take the path of least resistance, so you can end up with higher flow through the bypass hose, and lower flow through the radiator.