David Jenkins
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| posted on 8/2/07 at 11:48 AM |
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Crossflow cooling
When I'm driving along at any reasonable speed my engine temp is around 85 degrees. When I get stuck in traffic, it starts to climb to around
100 degrees. This is not a problem for 3 seasons of the year as once the fan comes in the temp doesn't go any higher. Trouble is, once the
summer comes it can go a bit critical - at least once last year I had to U-turn out of the queue to get some fresh air back through the radiator
(recovery is quick though). I haven't thrown any water out yet, but I'm sure I will eventually.
It's a good-sized rad (Polo), it has a proper and energetic fan (i.e. not a scrappy recycled one) that is about as large as you can fit, and it
does blow air through in the right direction  . There is also a decent amount of space to let the air out of the engine compartment. The water hoses
are fairly short with very few bends.
Now is a good time to sort this out, before the weather warms up (will it ever...).
First of all, is that "Water Wetter" stuff any good? Can it be used with anti-freeze without problems?
Are there any other things I could be doing to aid cooling while stationary?
cheers,
David
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flak monkey
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| posted on 8/2/07 at 11:52 AM |
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Water wetter is pretty good stuff, and can be used with anti-freeze mix without a problem as far as I am aware.
I know my pinto over heats (polo rad too) if you just leave it ticking over without the fan running once its up to temp (could cause me probs) but
once the fan is on it holds a nice 85 deg. So I would be interested in any good suggestions here too 
David
Sera
http://www.motosera.com
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DarrenW
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| posted on 8/2/07 at 12:15 PM |
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Im running my Pinto through old Micra rad and no expansion tanks with no real issues. Ive fitted seperate fan switch for those occasional traffic jams
in hot weather for piece of mind but havent experienced any real problems. It has been know to push some water out when really hot but thi swas cured
with a bottle connected to rad cap overflow.
On the DD2 it maintains approx 95 degs no problems with thermo fan switch. On track it has recorded 110degs for a short time but didnt show any
adverse signs.
The only time i have been slightly concerned was after a 3 hour run to Stoneleigh then sitting in traffic for 20 mins or so but the manual switch
helped to control things no problems. Its just a case of thinking ahead and flicking the switch on whilst still moving before you hit the thick of the
congestion.
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macnab
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| posted on 8/2/07 at 12:26 PM |
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when sitting in traffic make sure you are not right up close to the car infront as you'll be sitting in the heat from that car as well which
will make matters worse, plus when cars are too close the wind tends to go over the tops of the cars rather than around them.
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trialsman
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| posted on 8/2/07 at 12:35 PM |
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Make sure no air goes around the radiator. My xflow Escort rad had no blockoffs around it and I overheated all the time. I put metal and rubber
gaskets between it and the nosecone and all my overheating stopped. It was amazing. Russ
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MikeR
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| posted on 8/2/07 at 12:38 PM |
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in theory the rad shuold easily be able to cope with a crossflow so ...
wrapping the exhaust might help but there was a thread recently about something similar, how have you got the bypass from inlet manifold to water pump
plumbed in?
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John Bonnett
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| posted on 8/2/07 at 12:52 PM |
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I agree with Trialsman. It is important to make sure that all the air passes through the radiator and is not taking an easier route around it. On the
Special which is a 7 type, I boxed in the space between the radiator and the nosecone and on the Phoenix made up ducting.
As a trial, just put cardboard around the rad and see if that makes any difference. If it does, that's the solution.
John.jpg)
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miegru
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| posted on 8/2/07 at 12:53 PM |
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I have the same problem in my audi powered westfield, also with a polo rad.
The dutch westfield dealer told me that this can be fixed by closing the space between rad and nosecone; forcing all air to go through the rad.
(as mentioned by Trialsman)
Another solution I was told about is to replace the waterpump by an electric one running a full speed all the time (with an off engine mechanical
thermostat).
Myself; I'll try shrouding the rad first.
Mies.
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David Jenkins
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| posted on 8/2/07 at 01:00 PM |
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I'm not sure that would be the problem - if I was overheating while on the move then I'd agree that maybe the incoming draft is bypassing
the rad. However, my prob is while standing still, so it's down to the amount of air that I can push through the rad. Warm air might be going
around from back to front, but the gap is quite tight and there's plenty of places where the hot air can exit elsewhere. I can certainly try the
cardboard test first though.
I do have the bypass hose in place (I'm usually the one advocating that it should be there!).
Now that I've given this a bit of thought, I might try a few things to start off, based on some of the ideas put forward so far:
1. Fit a manual fan switch, so I can get it on early.
2. Change my front grille - it works when at speed, but it may be offering too much resistance for the fan alone (if you look at the weblink below
you'll see what I've got at the moment).
3. Try the rad shroud using cardboard.
4. Maybe try Water Wetter - but I'm not bothered about the temps when I'm on the move, so I don't want to affect that.
Any more good suggestions? 
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bartonp
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| posted on 8/2/07 at 01:04 PM |
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I can see how making sure all the air goes through the rad would help when moving....but when stopped? With the leccy fan on (presumeably vey close to
the rad)?
On a different tack, you could try a higher poundage rad cap to allow your water to boil at a higher temp.
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David Jenkins
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| posted on 8/2/07 at 01:05 PM |
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I've not boiled it - yet... (fingers crossed...)
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John Bonnett
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| posted on 8/2/07 at 01:06 PM |
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I'm quite worried now because if it is your grille that is causing the problem, the grille I'm planning may be the same. I could and still
could make a grille from stainless steel wire like the Caterham but I am planning horizontal slats and they will reduce the intake area by at least
50%. However, I read somewhere that the air exit vent should be twice the area of the intake. If that's true, I fail on that count too.
Shall be interested in what others have to say.
John
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John Bonnett
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| posted on 8/2/07 at 01:33 PM |
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David, I've just had a thought.
Has cooling when stationary always been a problem?
If so, is the fan turning in the direction it was designed to. I know some fans can suck or blow but others cannot and might therefore not be moving
as much air as as it might, if you see what I mean
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David Jenkins
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| posted on 8/2/07 at 01:56 PM |
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I thought of that! It is going the right way, and does blow air out of the back of the rad.
Mine's a front fan, blowing air through, but you can have a rear fan that sucks it through - does either have an advantage over the other? Most
production vehicles have it in front, but that may just be for convenience.
It may not be anything to do with the grille - but something more open must help the cause. I've always fancied the sort of woven stainless
wire mesh you get on Bentleys and the like - but then I saw the price. Quite fancied having a go at making my own; probably all it would take is a
pair of shaped rollers to put the bends in the right place... one day, maybe.
Europa stainless mesh
Check out the price... + P&P + VAT. ! ! !
[Edited on 8/2/07 by David Jenkins]
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02GF74
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| posted on 8/2/07 at 02:22 PM |
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as has been said, even though the engine is producing more heat at speed, the faster turning of the water pump and most importantly thge forced air
flow is enuf to keep things cool.
when stationary things aren't so good.
you don't say what size engine nor tune but you shouldn't be having problems.
so
a) is the thermostat a good'un? cheap and easy to replace.
b) fan belt good and tight? water pump good? using standard size pulleys?
c) is radiator good - missing fins, blocked, clean inside?
d) any hoses kinked/collapsed?
e) what is the size of the fan?
f) is it in front or behind radaitor?
g) how are you channelling air in to the radiator and out again?
h) is radiator at an angle or vertical
i) is timing and fuelling correct? make sure it's right at idle
j) at what temp does fan kick in and then out?
the nose cone area is big enough, a simple wire grille is all you need - fancy stainless steel plate with holes may be blocking off too much air.
then floor between nose cone and radiator - can you seal that to funnel as much toward the rad.
a fan with shroud is best infront of the radiator; try to get the shroud as close as possible so no gaps - I used thin ali strips screwed onto
shroud as in picture, tilt your heads side ways
leaving the floor under the engine clear is enough to get rid of air not requiring vents.
not convinced there is benefit in using exhaust wrap but can be put on the list to do right at the end.
water wetter - easy and cheap, anti-freeze/water 50/50 mix; use deionised water from wilko..
just some ideas to try.
 
radiator shroud
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02GF74
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| posted on 8/2/07 at 02:32 PM |
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quote:
Originally posted by David Jenkins
Mine's a front fan, blowing air through, but you can have a rear fan that sucks it through - does either have an advantage over the other? Most
production vehicles have it in front, but that may just be for convenience.
no; to suck air, the best you can do is get a vacuum i.e. 1 atmosphere. To compress air you can get much much more than that. Ok, the ickle fans we
have don't have anywhere near that capability but should do better at pushing than if they were sucking.
And should the shroud be in front or behind? - the restriction is the same so it makes no difference.
BTW a shroud is v. important as it directs air more evenly through the radiator - remember there is a dead space due to the motor so if the fan is up
real close, you lose efficiency, a significant percentage.
mesh people I used, are either multimesh.co.uk or wiremesh.co.uk.
They like to sell is big sheets - you'll have to speak/beg for a smaller piec; I;d like to think they are cheaper than £ 99 per foot 
maybe a group buy type thing?
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GeoffT
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| posted on 8/2/07 at 04:24 PM |
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How's your ignition timing at tickover? I know when I was running a Xflow it gave smoothest tickover at 18 deg BTDC. Sounds a lot for idle
advance I know, but it was perfectly happy at this figure, and never gave any overheating probs at idle. Just something else you might want to play
with.....
Geoff.
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greggors84
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| posted on 8/2/07 at 04:41 PM |
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Halfords do a antifreeze/summer coolant mix. Might be worth a try.
Apart from that maybe exhaust wrap to keep the under bonnet temps down.
[Edited on 8/2/2007 by greggors84]
Chris
The Magnificent 7!
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David Jenkins
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| posted on 8/2/07 at 04:47 PM |
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quote:
Originally posted by GeoffT
How's your ignition timing at tickover? I know when I was running a Xflow it gave smoothest tickover at 18 deg BTDC. Sounds a lot for idle
advance I know, but it was perfectly happy at this figure, and never gave any overheating probs at idle. Just something else you might want to play
with.....
Geoff.
I did try a similar tickover advance as part of my Megajolt playing - the car wouldn't start - in fact it wouldn't swing over! I was
going to set up a 'starting advance' value, but the weather's prevented that experiment just now.
Tickover's something I've got to work on - it's not happy at anything less than 1000rpm. Of course, this could be a symptom of the
same problem!
For info - it's a 1660cc x-flow, GT head with small amount of gas-flowing work (just port matching), Weber 32/36 DGV down-draught carb, Fast
road BCF2 cam (main reason for poor tickover). Megajolt ignition recently fitted and running a slightly smaller crank pulley. Polo rad was new when
fitted, coolant was fairly clean when I last changed it, and all hoses seem good.
I had similar stand-still overheating problems with original standard GT cam, pulley and points dizzy.
If I had a fundamental coolant problem like collapsed hoses then I'd be having problems at speed. Even 20+ mph is enough to keep the temps
down. This is why I think it's an air-shifting problem.
Note that I don't want to over-dramatise this problem - it hasn't boiled yet - but I would like to be more relaxed when driving in stop-go
traffic.
[Edited on 8/2/07 by David Jenkins]
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GeoffT
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| posted on 8/2/07 at 05:26 PM |
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My engine setup was pretty similar to yours, was using a Kent 234 (mild road) cam, but with s/draught DCOE Webers. Ok, it would get hot(ter) with
prolonged tickover, but a minute or two with the fan running seemed to keep things under control, even in the height of summer.
One difference is though that I have fitted a couple of louvre panels in the top of the bonnet, these seem pretty effective in allowing excess heat to
escape - maybe something worth trying?
Geoff.
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rusty nuts
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| posted on 8/2/07 at 07:52 PM |
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David, have used Water Wetter in my tin top when towing in hot weather. It can drop the temperature by as much as 20 deg. Also have you thought about
changing the fan switch for one that cuts in at a lower temperature?
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David Jenkins
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| posted on 8/2/07 at 08:03 PM |
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quote:
Originally posted by rusty nuts
Also have you thought about changing the fan switch for one that cuts in at a lower temperature?
Fair comment - and an easy experiment!
I think I'm going to be trying a combination of factors over the next few weeks...
Cheers,
David
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Fozzie
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| posted on 8/2/07 at 08:48 PM |
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David, you have a U2U...
Fozzie 
'Racing is Life!...anything before or after is just waiting'....Steve McQueen
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907
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| posted on 8/2/07 at 10:12 PM |
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Hi David,
May I suggest a couple of tests?
Firstly, the pressure cap. Check that it will actually blow at the pressure that it's supposed to.
If it blows at 2psi (like Stewart's c/f Lotus) then you may be close to boiling.
If it blows at 10psi then you have a safety margin of several degrees.
Stewart had many harrowing journeys, paid to have the rad flushed, and bought an expensive new fan,
then found out the cap was too short for the rad and the spring didn't compress enough.
Secondly, the gauge may not be reading right.
If it's reading high, even 5%, then this thread could have started off with...
"It's OK in traffic, 95deg, but is 80deg a bit low on the open road?"
Check it all over with an infra red thermometer. The temp sender area may be 100deg
but the top of the rad may be only 90. the bottom, 70 or less.
You may be worrying about nothing.
A hot engine usually "smells" hot.
hth
Atb
Paul G
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stevebubs
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| posted on 8/2/07 at 10:42 PM |
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quote:
Originally posted by David Jenkins
When I'm driving along at any reasonable speed my engine temp is around 85 degrees. When I get stuck in traffic, it starts to climb to around
100 degrees. This is not a problem for 3 seasons of the year as once the fan comes in the temp doesn't go any higher. Trouble is, once the
summer comes it can go a bit critical - at least once last year I had to U-turn out of the queue to get some fresh air back through the radiator
(recovery is quick though). I haven't thrown any water out yet, but I'm sure I will eventually.
It's a good-sized rad (Polo), it has a proper and energetic fan (i.e. not a scrappy recycled one) that is about as large as you can fit, and it
does blow air through in the right direction . There is also a decent amount of space to let the air out of the engine compartment. The water hoses
are fairly short with very few bends.
Now is a good time to sort this out, before the weather warms up (will it ever...).
First of all, is that "Water Wetter" stuff any good? Can it be used with anti-freeze without problems?
Are there any other things I could be doing to aid cooling while stationary?
cheers,
David
Static timing would be my first check...
Then look for smooth flow round the main system...search for Gary Meade's post on similar not so long ago. His cooling issue was resolved by
moving the pipes around on a T-Piece....
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