Need more information on this. Have you access to flow rate tests? I'm dubious about this statement. On the face, sounds like dealer talk wanting them to buy their product.
no flow rate tests.... simple living in the real world experience.
1. Understanding my car and know its behaviour
2. Seeing the change after work done, admittedly forcing the issue for a change back to an oem product.
3. Getting my old car behaviour back
How do we know the new oem metal ones are any good?
Data logging diagnostics is our background and now having seen the results of the oem pump on at least 30-40 cambelt jobs.
And even recently helping a TT owner with the same issue recover his cars behaviour by changing an aftermarket pump back to oem.
Dealer Talk!!
our business is based around offering an understanding and professional service to customers and offering the best advice we can from the real world experience I mentioned above.
If not from personal experience well give you the best objective opinion we can from research and good judgement or not give an opinion at all if we cant be conclusive.
When a car comes in with problems and is running a cheap quality EBay Maf, coil packs clones from China, temp senders/thermostats from Mexico and Metal water pumps with different flow characteristics..... which one of those components can you trust to operate to the oem spec?
None of them are known entities, hence any diagnostics can take much longer to help a customer.
The advice above is given in good faith based on the descriptions given and without hands on review its only here to give some options to consider one of which being the pump.
Whilst its the one we all least want to hear by nature of the cost to replace you at least have now got 2 examples (me and one of our customers) to bare in mind after reviewing any of the other possibilities.
However as the lower hose staying cold has been mentioned then the thermostat should be reviewed first as thats what was changed last and presumably made this difference.
