talk to me guys..

 

1.8T engine transplant into a fairly tight engine bay, the cooling system is all kosher, no leaks, brand spanking new genuine thermostat and temp sensors not micley mouse pattern parts, basically what's happening is when the engine is idling for long periods it starts to overheat gradually getting hotter hotter like when sitting in heavy traffic, but when driving along normally it is rock solid stable temp at 90 degrees like i'd expect..

 

i've been reading up on the 12v electric auxilary water pumps on the vr6 engines and apparently they are also fitted to some 1.8T cars too, i'm certain this overheating issue i'm getting is something to do with the flow rate, some of the hoses and routing is not ideal because of the nature of it being a complicated transplant in a few places the coolant is trying to run uphill, i was thinking about adding a 12v pump to help it out..

 

i know this is a long shot on here, normally questions like this go unanswered

Im not familiar with the VR6 setup but could you have extra issues with flow by adding a second pump? If the flow rates differed could it not cause pressure imbalances?

 

If you have changed the coolant pipes to obtain a different routing for the felicia, would it be worth adjusting where the fan switch is? (again im guessing it has a fan switch). surely it could give a more accurate reading so the fan stays on for longer? if it was closer to the engine, then it maybe able to overcome any heat absorbed into the coolant pipes inbetween the radiator and engine? (depending on the pipe routing)

 

just an uneducated suggestion i hope it helps!

Check fans are running

yes it does use a thermo switch for the cooling fans, i've used 2x 10" slimline pacet fans wired in parallel and the fans do work too, moving the switch is a good idea i guess, i did consider using a twin stage switch too like you get on diesels, so one fan comes on early, then the other comes on at a different temp..

 

i think the problem is to do with the coolant trying to take the easiest path rather than travel uphill through the radiator

picure taken from underneath looking upwards

 

as you can see it's tight in there, the ally coolant pipe see here runs from the thermostat pipe on the front of the block to the bottom of the rad, in a golf/a3 etc it this pipe is more or less level or slightly inclined so that the coolant rises into the radiator, but in my case it's not ideal because the warm coolant is trying to go downhill

 

the other change that i made is running a hose direct from the top coolant pipe to the top of the expansion tank which runs on top of the intake manifold, in the golf/a3 this is a hard pipe which is attached to the front bulkhead, also the top coolant pipe where the top radiator hose i shortened by about 5cm too so that i could use a oem bottom radiator hose from a seat inca van as my radiator top hose.. the other thing which is not ideal is that the heater core is phyically higher in the engine bay than the expansion tank which makes it an absolute pig to bleed the air from the coolant circuit

 

You could fit a fan override switch so that you can bung the fans on when you feel like it.

 

Or, and this can sound dumb, but if you blip the throttle a few times to spin the water pump up, it'll get coolant flowing better and hopefully bring some cold coolant from the rad to reduce engine temps.

 

Might not be a solution to your problem but something to bear in mind anyway.

YES i think i'm going to do that as a temporary measure while i thiink of a better solution to it, i'll just a simple toggle swiitch in in parallel with the raditor fan switch for now, although like i said it's not a matter of the radiator not being able to cope, its more that the coolant is bypassing using the easiet route..

 

need to get my thinking cap on and read up on the thermosyphon effect