My 1991 240 with 300,000 has developed a mild rod knock. Plan on nursing it until next spring. The machine shop recommended that I stay away from additives like Lucas and use 10-40 Brad Penn instead. Apparently it's Kendal GT under a new name. They have had a lot of luck with it in their race motors and felt that the higher level of zinc would increase the likelihood that it would survive the winter. Has anyone at least considered using it?

If it is a rod knock, there is no nursing it along. It goes from mild to severe rod knock pretty fast.

As the other reply stated, additional ZDP won't be of any help. It does help pushrod engines for cam and lifter wear, but it will do nothing for rod knock.
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john

It didn't concern me until I changed the oil last spring. The motor had a definite knock that disappeared once I restarted it. For the last couple of years when the motor was run for a while it had a slight rattling sound at idle that has become more noticeable over time. I have been using MobilOne 10-40. Perhaps changing over to a conventional oil like Brad Penn will extend it's life until spring when I plan on checking the rod bearings. If it's worn beyond using standard bearing I will probably scrap the car unless I can find someone that wants a nearly rust free southern wagon for scrap price near Rochester,NY.

If you are actually going to check bearing condition, might as well slap in new bearings unless this is your only vehicle. As rod knock and pretty much all sorts of bottom end bearing wear is virtually unheard of in late B230f's unless another oil pressure problem caused the premature failure (or just that 1 in a million fluke) I would most likely just have a set of standard bearings on hand and put them in. We are talking $70 or so from Napa and they are returnable.

I know you are a knowledgeable and long time poster but are absolutely sure with is a rod knock? I only ask because it is so rare (though a few instance have been reported).

Onkel makes a good point. Rod knock is very rare in the b230f engines. Just out of curiosity, how did you determine it is rod knock? Use a stethoscope on the block?

My 90 had piston slap but that tended to lessen when the engine was warm. Rod knock is more violent sounding.

The rattle is more noticeable when hot. That said, I'm recovering from a back operation due to one of my many once youthful stupidities. So crawling under the car will have to wait for warmer weather. I'm also able to stop on my way home with the tractor for groceries and going to the gym. Last year I probably drove the car once a week.
Also on commercial diesel motors you can sneak out the main bearings by turning over the crank while running a shank through the oil hole. Will a similar technique work with the Volvo?
Should I also consider replacing the oil pump?
If I'm not up to repairing it in the spring I would like it to go to a good home. As I said it would be for the price I would get for scrap including the remnants of my 89 240 wagon haunting the shelves of my garage. So for those interested I will post it here when I make that decision.

If you have a real rod bearing issue, replace the rod bearings and put it back together. If you have a main bearing issue, pull the motor (though rolling a bearing is likely feasible).

If your oil pump is not producing good hot pressure replace it but I would suggest just replacing the pump pickup o-ring otherwise.

In an early post (like your last one) you were willing to scrap the car for requiring over-sized bearings (which cost the same as regular bearings)...so I am going on the assumption this car is of little value to you.

If the motor needs oversize bearing the motor will have to be pulled and the crank turned. Not only will this increase the cost but it is a job I am no longer willing to tackle. I do value the car.I painted most of the car a couple of years ago, including the vulnerable parts of the undercarriage so that it could endure the Rochester winters. I would like it to go to someone who has the will and expertise if the crank needs rework..

Vacuumhead asked -- "Also on commercial diesel motors you can sneak out the main bearings by turning over the crank while running a shank through the oil hole. Will a similar technique work with the Volvo?"
Yes, the Volvo main bearing can be pushed around--get them started by pushing on one edge (the one opposite the locating tab), then rotate the crank and it will follow along--maybe with a little nudge on the now exposed other end.
I'm making this post in response to Unkel Udo II's post regarding the advisability of changing out rod bearings that can be heard with the motor warm. In my own experience that will only be successful if the rod rattle is only heard when first firing up the motor. A rod rattle when warm usually requires machining the crank journals. The one time I let a client talk me into changing out rod bearings that were clearly heard when warm resulted in a quiet motor--for about 5 minutes (1959 Ford Pickup 6 cylinder). It may work but I have my doubts.
Others have probably suggested this -- are you sure it's rod knock? A split exhaust gasket on one cylinder can sound an awful lot like a rod knock. I'll be doing just such a job later this week - the client said his neighbor told him he had a knock - and it just might be - but pulling the plugs to make sure they were in properly revealed a boot with obvious exhaust exhaust damage. The gaskets will be in soon and then we'll see. -- Dave

Latest API SN spec for engine oils calls for slightly reduced amounts of Zinc and Phosphorus (abbreviated to ZDDP) additives to preserve the efficiency of the catalytic converter.

This is not a real issue for the OHC Volvo engines as they have large (wide) camshaft lobes and spring pressures are not great. (Cam/lifter wear is an issue in pushrod engines with flat tappet valve trains. Classic car catalogs often offer a ZDDP additive for those old engines).

The red block Volvos are pretty tough so you may be able to nurse it along for a while despite the rod knock. If the oil your shop suggests meets API specs for the year of your car (probably SG) or higher, it will be fine. And yes - stay away from additives. They risk messing up the chemistry that all those refinery engineers designed into the oil.

It would be a good idea to check your oil pressure with a mechanical gauge to be sure it's up to spec. The fact that your dash light goes out just means you have something more than about 10 psi!
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Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), and 2010 XC60. Also '77 MGB and some old motorcycles

Thanks for the input. I guess my biggest concern should be damaging the Catalytic converter.

The negative effects on the cat converters due to zinc and phosphorus in the engine oil only appear after high mileages of use with the oil. Unless you use some kind of "racing" oil with very high levels of those compounds, you should have no problem. Your engine was already using higher ZDDP oils from birth to 2010 when the API "SN" oils became the rule.

As John Sargent says, your main concern is the rod knock and how severe it may become.
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Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), and 2010 XC60. Also '77 MGB and some old motorcycles