I'm running a Polo 1.0 litre radiator mounted at the front, 1.6 litre rear engine. Running temperature is 95C. Rad is fully boxed in so that all the air going through the grille passes through the rad. I'd like to see a 10 degree drop in running temperature. 82 degree thermostat.

In your view, is the radiator I'm using too small and if so, can you recommend a higher capacity one that will not be too big to fit. Rough measurements indicate that I could go to 430 x 377 core size with little resriction on thickness.

Any suggestions appreciated, thank you

a better fan ,are you useing a 82 degree thermostat?

As I understand it, a fan makes no difference over 30mph. Yes, as stated, I'm using an 82 degree thermostat.

i think the polo radiator is plenty big enough for a 1.6. people on here use them in 2ltres i think.

From past posts, I notice that many of our number have faced running temperature problems and so it is disappointing that nobody has come in to say, "This is what I did to overcome the problem".

In the absence of any help, these are my thoughts;

When comparing the size of the 205 GTI radiator with the little Polo one that I'm running there is a big difference so is it surprising that we're running hot? A higher capacity radiator is needed.

Space is very limited but I can get a VW349 radiator in (I hope). This is fitted to 1.7 and 1.9 litre Polos so I hope it will solve the problem.

In case there is any interest in this topic I'll post the results.

This is interesting....
VW decided that the little rad was OK for a little engine, and a bigger one needed for the bigger engines. Makes sense....
I suspect by sheer luck that the little rad gets extra airflow or whatever in many of the kits, but with cooling I am very much on the side of having "over-engineering"
Yep, my zetec ran the rad off an 1800 golf thingy, and was just about adequate..... I effectively ran the rad upside down, the only difference being the position of the fan sensor, which wasn't being used anyway. Not sure if the polo rads will be the same in this respect, they may be as I think the small vw engines are fitted the opposite way round to the larger versions.

Was talking to a mate who's built a Mojo, Honda engine in the rear, front rad. He had cooling problems, and reckons the engine driven water pump is not up to the task. It's either the volume of water, or the distance it has to pump it that causes problems.

Anyway, his fix was an electric water pump, cooling problems gone.

Thank you for your replies. I too had wondered about the water pump and am interested to hear that an electric pump solved the problem for your friend. However, the thing I have noticed is that the water temperature gauge (mounted on the engine) agrees well with the temperature (radiator mounted thermo switch) at which the fan cuts in. This suggests that there is adequate circulation and that the temperature of the whole system is pretty consistent.

I've just received my new radiator, VW349, and it looks much more up to the job being larger in all dimensions than the one I'm using so I'm hopeful it will improve the situation. We know that this radiator is used on 1.7 and 1.9 diesel Polos so if there is still a temperature problem then it won't be the radiator.

For anyone who might be interested the dimensions of the core are as follows;

430 x 377 x 23mm.

It will be two or three weeks before I can do the swap but will reopen this thread once I have some information to share.

..and post some pics please

I'll post some pictures including the two radiators side by side so that you can see the difference but as I said, it will not be for a couple of weeks.

The other impoprtant aspect is a pressure differential across the radiator. So either an under tray which helps air to leave the engine bay under the car or large engine bay side vents.

The last mod on mine helped noticeably with engine bay temps and especially the tunnel temps. Previous to the large vents the tunnel would get too hot to touch.

The floor goes right to the front of the car so, hopefully the rear facing side vents and bonnet vent should encourage pressure differential across the radiator. The thing I have noticed is that there is enough hot air coming through the bonnet vent reaching the windscreen to raise its temperature appreciably.

Now, here's the question. Is this because there is really good heat transfer or, because the air is not travelling fast enough through the rad and therefore heats up to a high temperature. ie, would a higher airflow reduce the temperature of the air hitting the windscreen? If so, is the temperature problem one of airflow rather than an inadequately sized radiator?