Keeping your cool with an engine conversion

[MJK 24]

I've got a little turbo diesel in my Scirocco. It's got an intercooler in front of the radiator. The pipes for this go around the radiator end caps each side.

At a high speed cruise, it's running at nearly 2/3rds on the guage. I'd be happier with it running a '5 past 12' which is where they run in the Mk2 Golf it came from. They have a huge radiator that simply won't fit due to its height.

I've got a petrol injection radiator, 526mm from memory.

The slam panel is drilled and threaded for 4 radiator sizes.

What size is a Scirocco 16v radiator? Does this go all the way over to the left hand chassis leg?

What do people use for radiators and intercoolers when fitting the 1.8T?

Any advice or guidance from someone who's solved this would be much appreciated.

Thanks you :)

[MikeH]

Different temp gauges can give different readings. and the sensors in your TDI conversion then the resistance ranges could be different from the original rocco ones. Which dash are you running? If you can get a laser thermometer on it, that would give you a second opinion. Is it showing any other signs of being hot - e.g. fan running constantly, losing coolant, smelling hot? If not, then it's probably a gauge issue.

It's possible that you have a cooling problem though...

I ran a stock radiator with about 150 bhp in an 8v petrol motor. It used to get the oil a little hot, but then I realised it was the original factory rad (20 yrs old), and the replacement was much better. If it's had radweld or other sealants put through the system, or just been run with the wrong or no antifreeze, it'll tend to block it up. Are you sure the thermostat is opening properly as well - bottom hose should be nearly as hot as the top hose, once the stat is open.

So, is your radiator in good nick? A replacement standard one might be enough. The ABF conversion in one of the other cars runs fine on a standard new-ish radiator.

If not, then there are various cars in the VAG range with slightly bigger radiators, e.g corrados, passats, etc, but you need to watch the connections to make sure you've got something compatible. I've got a Seat Leon TDI rad with twin fans to go in with the X-Flow conversion on the trackday car.

[MJK 24]

Hi Mike,

Thanks for taking the time to reply.

It's not a TDI, it's a 1.6 GTD from the Mk2 Golf. More in keeping with the era of car!

I'm running standard Scirocco clocks. I've checked the part number of my temp guage with the one in a Golf diesel and they're the same.

I'm running with the correct thermostat for this engine. It's genuine VW and only a year old. Had a genuine water pump at the same time. G12 coolant mixed around 40/60.

My radiator is a Scirocco injection, 525mm.

The next size up is Caddy diesel which is 570mm. All of the extra length in this radiator is accommodated in the gap between the existing radiator and NS chassis leg. In other words, although the coolant capacity would be increased, there wouldn't be anymore airflow to the radiator!

Next set up from here is a 675mm Scirocco 16v radiator. This is the same part number as a Mk2 Golf GTD radiator so in effect correct for this engine. Radiator would go from the NS chassis leg to within perhaps 5-6 inches of the OS chassis leg. This would gain some extra cooking as the 525mm radiator doesn't utilise all of the front grille.

To be honest I'm wondering if it'll always be a bit marginal on cooling having this engine in a Scirocco? A Mk2 Golf has a huge tall and wide grille whereas the grille on a Scirocco is basically the size of a number plate!

[Winston]

You could try a Mk1 Golf / Caddy diesel radiator. I ran one on my GTD caddy it did the job and they have the same problem air flow.

Maybe add a cold air feed? to the other side of the radiator?

[the edmundator]

You could improve cooling by getting rid of the inner lights. Your options then are a home-made grill, or fitting a set of the blanks use on early CL and GTS model - the latter would also need to be modified as they're solid, but I'm sure a bit of time with a dremel would work wonders.

[MikeH]

Hi Mike,

Thanks for taking the time to reply.

It's not a TDI, it's a 1.6 GTD from the Mk2 Golf. More in keeping with the era of car!

I'm running standard Scirocco clocks. I've checked the part number of my temp guage with the one in a Golf diesel and they're the same.

I'm running with the correct thermostat for this engine. It's genuine VW and only a year old. Had a genuine water pump at the same time. G12 coolant mixed around 40/60.

My radiator is a Scirocco injection, 525mm.

The next size up is Caddy diesel which is 570mm. All of the extra length in this radiator is accommodated in the gap between the existing radiator and NS chassis leg. In other words, although the coolant capacity would be increased, there wouldn't be anymore airflow to the radiator!

Next set up from here is a 675mm Scirocco 16v radiator. This is the same part number as a Mk2 Golf GTD radiator so in effect correct for this engine. Radiator would go from the NS chassis leg to within perhaps 5-6 inches of the OS chassis leg. This would gain some extra cooking as the 525mm radiator doesn't utilise all of the front grille.

To be honest I'm wondering if it'll always be a bit marginal on cooling having this engine in a Scirocco? A Mk2 Golf has a huge tall and wide grille whereas the grille on a Scirocco is basically the size of a number plate!

Yes, but how old is the radiator you have? Have you checked that the thermostat is actually working properly? Are there any signs of overheating other than the gauge? The gauge is old and could be mis-reading a bit.

The hole in the grille doesn't have to be as big as the radiator (and there are other holes under the bumper) because of the back pressure effect of the rad itself. It only has to be about 1/4 size of the rad to get max airflow through it (so I'm told by an aircraft engineer I know). \

If my 150 bhp ABF conversion works on a stock radiator, I don't see why your 75/90bhp diesel shouldn't be OK.

[MJK 24]

Radiator is 18 months old. Thermostat is working - warms up nice and quickly in cold weather. Can normally feel heat at the vents within half a mile and that includes when it was -10!

I think a bigger radiator must be a natural next step? If VW could have got away with a 525mm, I'm sure they would?