Overheating had water pump & timing belt replaced ~ 1998 Volvo s70~ now it overheats in about 10 minutes of driving.~ no more leaks, water is boiling hot in reservoir tank !~

SOURCE: Replace Heater Core for Volvo S70 (1999)

It is your heater core. I fixed mine for $144. Ordered the new part on Ebay and followed these instructions http://www.volvospeed.com/vs_forum/index.php?showtopic=9717 It was very simple, I'm a middle age grandmother! The hardest part was cleaning up all the antifreeze. You will need a shopvac, a small one is $20 at WalMart.

SOURCE: 1998 volvo s70 heater smells strange and smoke fills the cabin

Your heater core is leaking. The smell and smoke is from the coolant evaporation.

SOURCE: how to replace fuel pump volvo s70

http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c1528008c73c

SOURCE: volvo s70 radio code

what is the radio code for 1998 vovlo s70

SOURCE: diagram of timing belt on 2000 volvo s70

Sorry for the delay.
I am personally going back to answer your unanswered question. I do not know if you still need the answer, but I am going to answer it in case you still do.

Click on the following direct Link. It has the Timing Belt/MARK(S) Diagrams that you will need, complete with Instructional and Directional Diagrams.

Again my apologies...
Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!
http://www.2carpros.com/car_repair_information/year/1999/make/volvo/model/s70/1999_volvo_s70_timing_belt_diagram_marks.htm