How many miles does your car have on it? Is it a turbo? What brand of oil did you put in?

Piston slap is common in red turbo engines. Does it get quiet when it warms up?

I have had poor experience with inexpensive oil in high mileage cars. As a result, I never use inexpensive oil or filters in my Volvos. I bought 10 pack of filters at a great price on ebay from a Volvo shop.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 415,000 miles put on 9 bricks

Hey WW. I know exactly what you are talking about. I won't say it is common in the B23 or B230 but neither is it uncommon. I've heard various people say things like 'developed from agricultural engines' and such. I don't buy this because agricultural or not, most production engines have similar tolerances and aren't supposed to make any major knocking noises. About oil: I run 10-40 in everything I own and our temps here run from the low twenties in the winter to over 100 in the summer. If we were below zero in the winter I would go to 10-30. One needs to keep in mind what "multi-vis" means. Those two numbers refer to weight. I don't think oil is the issue. Did changing the mounts make it easier to hear/feel some noise? Maybe so, not unusual. The issue is: what in the engine is rattling. You either have a rod big end bearing issue, or piston slap in my opinion. I'm a big fan of Auto-RX. Not only is the stuff great at reviving seals and gaskets (especially seals) but it is great at cleaning out filthy engines, clogged ring packs, flame traps, oil separators etc. If you have gummed up ring packs from low speed operation or from incomplete warm up (possibly prior to your ownership?) then your pistons will slap. Sometimes getting the engine warm helps, sometimes not. On a couple of occasions I've had the additive eliminate such a noise problem. One was a car that rarely saw more than 1/2 hour of use. Second bottle of the stuff, about 500 miles into the oil change, on the freeway one day at about 70 the car began to smoke badly. Dark gray/black. Speed dropped, car seemed to be starving. All of a sudden it cleared up and the power came back. Car stopped knocking at idle after that. I believe the additive released a bunch of garbage that was binding the ring pack(s) and causing piston slap. Try it! Auto-RX.com I keep it on the shelf and add a couple ounces with every oil change--and I am not one to buy 'remedies' usually.

DS

Pinging? Take a can of wd-40 and spray it at your injectors and see if the idle changes, if it does change the seals. I have had to do this a few times and I am getting really sick of pulling the stupid injectors out so make sure you clean the crap out of everything and then run a little vasaline on the seals so they don't rip when you put them in. I have never heard my car be referred to as a red block but the block is red and it's the same year as yours so I would assume this applies.

If thats not it it could be a pump making noise, my ac pump is really noisy especially when its cold. I run castrol 10-30 during the winter and 10-40 during the summer. Its hard to tell where the noise is coming from but just listen to what side of the motor it is coming from. Also one other thing, if the car is missing at an idle it could be another tell tale sign of bad injector seals. Make sure you get the inner and outer seals probably won't run you more than 10 bucks for 8 seals, and a couple hours of time if you have never done it before, I can change 4 injectors and 8 seals in an hour 15, just do it right the first time you don't want to get really good at it :).