1983 308qv With the help of Steve from Arena motors, we traced a whine in the cockpit to the oil cooler touching the body/vent. we shifted the oil cooler a tad & the noise stopped. But...... There is still a hi-frequency vibration on both steel oil cooler lines and hence the cooler itself. You can easily feel it just by touching either line or cooler. it isn't a vibration like the cams or plugs firing, but a much higher frequency. Like some sort of oil "Valve" that is stuttering. Start the car & all is quiet for about 1 minute then the vibration starts sporadically, then 30 seconds later stays on. The effect is more pronounced at the cooler than at the block where it is almost non-existant. We flushed the cooler lines & cooler unit, but not a significant difference. I've replaced the oil filter...no difference. Oil pressure & level are fine. dino 20w50. Any ideas? Next out is a replacment cooler.
Clyde, Before you go replacing the cooler, I believe there is an oil pressure relief valve somewhere in that system. You might want to check that, make sure it is not either failing or clogged with gunk, causing the oil flow to oscilate. Just a thought. Steve
Thanks Steve. I suspect if such a valve exists, you are on the money. Anybody know where such a valve is? I have an extra cooler, so swapping it would be no biggie.
The relief valve is under #29, 27-31 are the parts your looking for. I would also look the hoses over very carefully. If one has ruptured internally it could be expanding and relaxing in concert with fluctuations from the pressure relief valve. Also think about swapping oil filters. I had one thumping once, and when I replaced it it never did it again. Image Unavailable, Please Login
Thanks Paul. I'll be checking that tomorrow. When we had the oil cooler lines off, they looked fine to the naked eye using a microlamp inserted into them as did the cooler itself. A different Baldwin oil filter had no effect.
Paul makes a good point. If the interior wall of the hose has started to separate, it can create a flap inside the hose that will fluctuate like that. Since it seems to develop after you build pressure and flow, my thought was the pressure valve, but could also be an internal problem with the hoses. Worth having them checked or even replaced. Having a hose company rebuild them for you is pretty cheap.
Look inside the cooler via the fittings and see if the transfer tubes extend more than 1/16 inch into the tank area. The were batches of oil coolers where the tubes extended at least 1/4" into the tank and it was common for these coolers to squeal when the oil was thick. The noise is generated by the thick oil turning right angles and lining up with the extended tubes. Coolers where the tubes were flush with the tanks in turn making it easy for the oil to enter into them were quite under all conditions. In the early 80's we would have to order a batch of coolers to get a few good ones. Knowing what causes the noise, if it doesnt bother you, leave it. I have never traced it to any engine oiling related problems. Dave
