Hi

 

The background of my issue:  Car is a TDi110 and has a hybrid turbo, with remap and turbo is running at 1.7bar.

 

On one occasion i was driving under load, and the temp crept up to 3/4 - after slowing down, it returned to mid way.

 

I pulled over and noticed that the bottom hose was cold, and the top hose was hot.  I drove home with fans on full heat to remove some heat from engine.

 

The thermostat was changed (have changed 3 times - in the end using a genuine) but the issue still persisted.

 

By this time, i was getting mayo under the oil cap, so headgasket was renewed, head decoked and pressure tested, then everything put back together using arp headstuds in case the head was lifting.  The waterpump was replaced 5k ago.

 

Everything has been put back together, and on idle, it takes about 20mins to get upto temprature and fans turned on.  However, when driving, it only takes 1 mile to come up to temp (was around 6-8 miles before), and i still have the same issue - mayo in cylinder head, and bottom hose not warming up.

 

I have tried a cooler running thermostat, and that opens, but i noticed that the rad is cool to the touch.

 

Any ideas on what it could be?  ive done a pressure test and it all seems fine and holds pressure whether hot or cold.  I have to top up the coolant on a daily basis if it is driven.

You've never gone near the real problem, other than touching it, I think.

 

I can't say which from what you've said, but I'm virtually certain that either the base of the radiator or the bottom hose is blocked.

Was the pressure test done cold? If there is still oil in the water I would say there is a leak between an oil way and water way. If the bottom hose is cold that points to water pump. Check the return to the header tank for flow and if possible to a pressure test when hot as if there is a hairline crack it will open up when hot. With a the problems listed and still the same there must be something underlying there. Hope this helps in some way?

ive backflushed the rad and all seemed fine.

 

ive taken out the thermostat and i had flow, and rad got hot.

 

i am getting flow from the waterpump, and pressure tests were done hot and cold!

Check top and bottom hoses for internal collapse when hot. Try squeezing the hoses - is the resistance the same all round and all along the length?

the bottom hose is often cold but solid