The Stovebolt Site Forums The Shop Area Engine Shop Hydraulic Lifters

A friend of mine has a 41 1/2 ton with a 235. He's having a problem with his hydrolic lifters. After running at 45 mph for a short time they start clacking. It appears that they are bleeding out. I have read that this is a common problem with 235s and hydraulic lifters.

What I'd like to know is if anyone has a solution (other than going to solids). Is there something we can do to the lifters to keep them pumped up? A high flow oil pump was suggested but I'm not sure that would work, and may blow oil past the rear seal.

We need some suggestions.

Thanks
George

What's the oil pressure? If it's getting low when the engine heats up, that's why the lifters are bleeding down. Where did you get the idea a high volume pump will cause seals to leak? None of the crankshaft seals have oil pressure applied to them, so there's no way more pressure or volume will cause leakage.
Jerry

Jerry - I see what you mean about no pressure on the seals. I just heard that somewhere, obviously I didn't think it through very well.

So if we're getting low oil pressure you are saying that a high volume oil pump might help.

How about the weight of the oil used, would this cause the problem?

I'm not too good at diagnosing problems, just trying to help out a friend. Any suggestions sure would help.

Thanks
George

Unless it's a fresh rebuild, it's hard to beat plain old HD 30 weight oil in a 235, especially in the summertime. It gets a little thick on a cold winter startup. I've used 20W50 year-round in a lot of engines. The 10W30 and other multi-weight oils don't actually thicken up as they get hot, they just lubricate like the heavier weight rating. So, a 10W30 stays the thickness of a 10 weight all the time, and if there's a lot of clearance, oil pressure will drop as things heat up.

A fresh rebuild with very close tolerances can use the lightweight stuff without a problem. A high-volume oil pump will flow more oil hot or cold, and the pressure will go pretty high on a cold start. Once things warm up, the pressure will still drop, but not enough to let the lifters bleed down.
Jerry

May have to disagree about the higher pressure not making the rear seal leak more. If the mains are worn enough to merit more oil pressure with a more agressive oil pump then the oil has to go somewhere. If that rear bearing has enough slack to let much oil by, then some has to get to the seal. If the oil can't drain off the seal fast enough, it has to go somewhere, usually out. Kinda like what happens to the automatics when the front pump bushing gets bad, sometimes will push the seal right out.

If oil pressure is low after the engine is warm, it's time to look at bearings at the very least.

The 235 hyd. lifter problem has been very common with aftermarket (non GM) lifters. Seems to mostly be caused by air getting in the lifters. Solutions have included grinding vents in the lifters and taking measures to insure airtight sealing of the pickup to oil pump and oil pump to cap etc.. None of these have really worked for me. May be more on the Inliners site.

Thanks everyone I'll pass on your suggestions. There is a similar thread going on the Inliners site that I'm keeping an eye on.

Thanks
George

Hotrod, a 15W40 has the same viscosity at 100C as straight 40. Multiweight oils don't thicken up, they "thin" less.

OK, so how do they flow like a 15 weight at low temps? Your logic doesn't even make good nonsense!
Jerry

Check out the technical datasheets published by Rotella. Rotella has them for both straight and multiweight oils. You will find that the higher number of a multiweight is indeed the viscosity at 100C.

I found this during a cursory search on the internet: Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

I have compared straight 30 with 15w40 and found the oil pressure to be higher with the 15w40.

Hopefully, your ignorance can be fixed lest you remain stupid forever.

Okay Jason, couldn't let this go. You were doing okay for awhile there and then had to add that last line.

Got to tell you up front, Hotrod ain't no where near being stupid. Don't know him personally, but do know he is very knowledgable. Has given me lots of good advise, and a good person to know to ask questions.

Thanks, Roy!
After 35 years of teaching school, I've learned to ignore cheap-shot artists!

Jerry

It was a play on HRL's signature. Not to have been taken so seriously.

Two deaths this month have left me a little off.

Barry Weeks knows the answer,it's a design flaw of the oiling system.The old timers used to trash can the hydraulic lifters,put in a set of solids,the cam didn't seem to care,nothing wore out or was clackier that normal.
A 235 has several large oil drain holes in the rear main cap area between the rear bearing and seal so oil pressure can never get at the rear seal.
There is no after market high volume pump for 235's,you can use a 228-302 GMC oil pump to give more oil flow if needed.

You need to tell my 261 that oil isn't supposed to get to the rear seal. Pours out the back when running. (Engine has nearly thirty years since the rebuild). Doesn't smoke so may just replace the rear seal and check the bearings for the heck of it. Still has 60+ lbs of pressure at startup, and 25 at idle after everything is good and hot. (using 1030w all year round)

Plenty oil gets at the rear seal,it's not pressurized ,when you pull the pan you"ll see why.

Roy- I've done "extensive scientific research" (well, I've putzed in the garage on it) on the leaky 216/235/261 rear main seals. I've tried just about everything. I know that leaky rear main seals are not caused by too much oil pressure or excessive crankcase pressure. Both of these are easy to check. Pull the trans./bellhousing/flywheel off the back of your engine and use a dummy distributor shaft and a drill to spin the oil pump and build oil pressure. You can bury the needle on the oil pressure gauge this way with a good fast drill motor. Watch the rear of the motor for leaks. Watch it for hours if you want while the drill spins, it still won't leak. Not oil pressure related. Build a brass slinger that bolts to the rear main cap and wraps around the rear crank diameter and protects the rear main seal from oil under pressure coming through the rear main bearing. No change.

To test for the buildup of crankcase pressure, I first cut apart my roadpipe and cleaned all the baffles and welded the assembly back together. No change. Then I built a simple PCV system to draw any pressure and fumes out of the crankcase. No change.

I believe the leaky rear main seals are caused by not enough press or squeeze on the rear diameter of the crankshaft by the seal. I think the current seals (made by Fel-Pro, even if you buy another brand such as Victor) don't fit tight enough. I also think that a rope type seal will work better at first (as it has plenty of press), but will eventually wear in and need replacing. The old asbestos rope type rear seals will last longer, but will also wear in and need replacing, especially if the vehicle is not run regularly and sits.

My current theory (which is most likely wrong again, as usual) is that the best way to seal an early Chev. 6 is going to be a large 1-piece seal as used on the newer Chev. V-6's and V-8's. Someone did an article on machining a block for this style of seal in a past issue of the Inliner's magazine. (The 12-Port News) I think if we could cut a window in the side of an oil pan and take a peek while the engine was running, you would be amazed at all the oil flying around. The crank is thrashing the hell out of the oil in the pan. I think it takes a real positive seal to keep oil from slipping by and getting on the back of the flywheel where it gets slung around the bellhousing, and eventually ends up dripping out the drain hole in the inspection cover after you have parked the truck.

Barry, I'm sure you are probably correct. The problem with my 261 is that the two piece rubber seal put in nearly 30 years ago just doesn't seal anymore. It has most likely gotten old, hard, and just flat lost what sealing properties it had a few years ago.

It didn't leak for many years, but has gradually gotten to the point that it will have to be replaced. Engine has no blowby, even though it is nearly 30 years old now since the rebuild. (Only about 25,000 miles over that time on this engine.) Could be this engine wasn't run enough to keep the seal pliable longer.

I need to do some clutch work, as well as other maintance to this engine and will simply pull engine and trans as a unit and replace the seals both front and rear as well as some cosemtics under the hood.

I thouroughly enjoy this old pkup, and most certainly enjoy that 261. A little later I'll put some better gears for highway use so it will pass gas stations more often than stopping.

Jason: Thanks for that oil info.

Hotrod Lincoln: I don't think that Jason was trying to be rude. He was just joking. Misunderstandings with the written word are common. That's why good writers are coveted. :•)

The day we stop learning from others is the day we die.