TurboD JR: Thermal Issues and Solutions

hello,


'My VW Caddy 1 was converted by the previous owner from a 75 HP gasoline engine to a turbocharged diesel engine (70 HP, JR from a Golf 2). Besides the engine itself, the previous owner didn't change anything; the radiator, fan, exhaust, etc., all remained from the gasoline version. After about 3,000 km, the engine failed. It wouldn't start anymore, and the compression was extremely low (between 8.5 and 19 bar). The head gasket had blown (very high water and oil consumption).'
I've now installed a used engine with approximately 120,000 km (75,000 miles) on it. I've also installed a larger radiator with a more powerful fan motor from a Golf 1 TD.
The engine is running well so far, starts easily, and doesn't consume any water or oil.

The temperature gauge still shows 'too high' a reading. That is, the needle is always above the middle mark and sometimes even reaches 'three-quarters'. The fan also eventually turns on if I let the engine idle.

So far, so good. However, I've always wondered if it's normal for the needle to be so far to the right. Also, the fuel gauge from the gasoline version is still showing on the dashboard. Does it need to be 'recalibrated'?

Here's the translation:

'The issue with the exhaust manifold connection to the downpipe was resolved as follows: The original exhaust manifold with turbocharger from the Golf 2 remained in place. The flange on the downpipe was cut off and replaced with the one from the Golf 2. The downpipe has a diameter of 42mm, which the workshop confirmed is perfectly fine and corresponds to the measurement for the Golf 2 TD. Does anyone know anything else? Could the exhaust system be the cause if a TD engine overheats?'

'Or does anyone have any other ideas why a diesel engine might overheat (e.g., fuel pump or something)? What could be the cause? Or is the temperature actually normal, and the gauge is reading too high because the instrument panel from a gasoline car is still installed?'

I really need your help, because I don't want to ruin another engine! The whole process was expensive enough already.

I know that converting a Caddy to a TD (JR with 70 horsepower) is one of the most popular modifications. So, TD drivers, please share your experiences.

'Thank you very much in advance.'

Why don't you measure the coolant temperature at the location where the sensor is?

Okay, so I replaced the radiator on my Golf 2 because the old one was leaking. Try removing the thermostat; it might be clogged or faulty, especially if the cylinder head gasket is damaged.
I also installed a Golf1 TD radiator, and it's almost twice as thick as the standard Golf2 radiator. From that point on, the water temperature was always just slightly above the middle (unfortunately, I no longer have any measurement data), and overheating was no longer possible. It's a 'super' radiator.