This place is a godsend, I can alway find the answers here, thanks a billion! ? it has been below normal this past two or three weeks, and I been going insane with my jetta tdi. I had the tb, wp, and ts done in late September. I am usually not cold, so I use my heat infrequently, but the past two weeks I have noticed that it takes over 20 minutes for my temp to reach 150/160 range. If do turn my heater/defroster on, it only blows cold air. My son is in tech school to learn vw mechanics, so he changed my oil in December, and in an effort to save himself time latter on he left off my top engine cover(the plastic cover on top of the engine). Will putting the cover back on make a difference? I am definitely going to try the foam in my grill, but am curious if I should also put the cover back on. Could a ts go bad in three months?