I just added a 745 Turbo to my Volvo rear drive fleet. I have an 87 245 with 312K, a 93 945T with 200K and now, a very sweet 745T with 200K. The turbos have AW 71 automatic trannies and the standard 230FT 4 cylinder engines. The 745 has a Garrett turbo and everything under the hood looks original, including vacuum and intercooler hoses. The new addition runs fine, except when I get on the turbo. Boost looks normal...the guage works and climbs from black to orange to red as I accelerate. However, as boost increases, I'm getting a pretty loud high-pitched whine and the engine hesitates, then stumbles and boost disappears. I'm not blowing smoke (white, black or blue). Thus, the only symptoms of trouble are the whine and the stumbling. The harder I get on the turbo, the worse the symptoms.

I suspect leaking turbo hoses, but would like some thoughts from listmembers regarding diagnosis and repair.

Thanks in advance

I don't know about the whine - but the stumble I have on the 89 760 I just bought. It too has the Garrett.

You might try to check the small red check valve (in the vac line) between the BOV (by the #1 cylinder) and the intake manifold. It is supposed to have resistence when you blow through it both ways according to the FAQ's. I have a new one on the way as mine was showing bad.

One of the comments in the FAQ's said that this fixed the stumble prob.

Another thing that I am going to check ASAP is the RSR (radio suppression relay). Check this link.

http://www.brickboard.com/RWD/index.htm?id=929131

Be blessed in your quest!
--
'89 764 (110K), '94 940T (180K) , '92 745T (totaled 2-10-05 RIP)

my experience...if it sounds a bit like police siren spooling up as the boost climbs (kinda cool) its kinda expensive...shot bearings in the turbo...DO IT NOW you MAY get away with a recon, mine was so shot i had to have new turbo...PO had left it too long....