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Melling High Volume Oil Pump for Type 4 Motor
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SGKent Premium Member
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PostPosted: Mon Jun 18, 2018 8:15 am    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Quote:
A pity Melling don't list even the most basic technical info on their products, which adds to the confusion.


Melling says in their catalog clearly what their pumps fit and what the purpose is. They don't list a T4 application nor do they have an obligation to provide detailed measurements to the market. Perhaps what you really mean is that it is a shame an inexpensive stock pump is not available. So goes life with a 50 year old car. The T4 AC engine has been out of production about 35 years.
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PostPosted: Mon Jun 18, 2018 1:57 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

I don't know where this comes from, and normally I leave such remarks uncommented. I love the civil technical discussion, learning from folks I admire and respect here, and giving other fellow bus drivers a hand if I possibly can. I just don't see the point in getting angry with people on the Internet.

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SGKent wrote:
Perhaps what you really mean is that it is a shame an inexpensive stock pump is not available.


So just for the record, I neither said nor implied any of this Smile
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PostPosted: Mon Jun 18, 2018 2:48 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Sometimes I have to take a break.
Tcash
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PostPosted: Mon Jun 18, 2018 3:44 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

furgo wrote:
I don't know where this comes from, and normally I leave such remarks uncommented. I love the civil technical discussion, learning from folks I admire and respect here, and giving other fellow bus drivers a hand if I possibly can. I just don't see the point in getting angry with people on the Internet.

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SGKent wrote:
Perhaps what you really mean is that it is a shame an inexpensive stock pump is not available.


So just for the record, I neither said nor implied any of this Smile


Because so often we can just accept a vendor or manufacturer’s word that a part will fit. No need to bother our little heads with specs...

I don’t think SGKent’s comments were intentionally negative
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PostPosted: Mon Jun 18, 2018 4:23 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Tcash wrote:
Sometimes I have to take a break.
Tcash


...
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PostPosted: Fri Jun 22, 2018 3:10 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

The M79C gears are 1.002”...25.45mm

Hmmmm...
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PostPosted: Fri Jun 22, 2018 10:10 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

And this is what I got from Melling tech enquiries. No information about actual sizes, though:

Quote:

M-79A, and M-79B both use the same gears, M-79C has taller gears

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PostPosted: Sat Jun 23, 2018 3:37 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Posted the question to Summit Racing. This was the reply.

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Looks like it could be a good alternative.
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PostPosted: Sat Jun 23, 2018 5:26 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

furgo wrote:
And this is what I got from Melling tech enquiries. No information about actual sizes, though:

Quote:

M-79A, and M-79B both use the same gears, M-79C has taller gears




See.....this is what I hate. Summit is saying according to what they replied to Orwell84.....that the M79C....is 26mm (1.02").....and that tbe other two are shorter.......yet mamy adds list at least two if not all of those pumps....are typically advertised as 30mm gear length.

Mine is 30mm gear length.

But....IAP....says the M-79A is 21mm.gears
http://iapperformance.com/melling-m79a-oil-pump-21mm-gear-8mm-stud-flat-camshaft.html

IAP also lists the M79-BHV as 28mm

Perhaps the Summit guys are right.....in the extent that the M79C has the longest gears....but it aint 26mm....if those other two are 21 and 28. Ray
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PostPosted: Thu Jul 19, 2018 9:12 am    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

So yesterday, after a long drive at highway speed (about 2 hrs at 65MPH avg.), I'm going through a little town in Central TX and my oil light starts flickering at red lights. Ambient temp was 102 deg F. As a refresher, I have the stock oil pump on a stock 1978 2.0 L fuel injected bus, and I'm running Shell Rotella T6 full synthetic 5W-40 diesel oil. Never had the oil light flicker before at idle in similar heat, but to be fair, it was really, really hot outside, and I had been driving at sustained high speed (for a bus). I pulled into a local Walmart to get a bottle of STP oil treatment to thicken up my oil. That cured the low pressure at idle problem, but it got me thinking again about the Melling oil pump.


Have others actually seen higher oil temps with the bigger Melling pumps / vs the stock type 4 pumps? I mean, under the same conditions (which is hard to control). I understand all the fitment issues and leaking, and I get that the higher volume will open the bypass valve, if the pressure gets too high, and also bypass the oil cooler, but it's not like ALL the oil bypasses the cooler when that valve opens. I would think the oil pressure in the rest of the system stays at whatever the valve opening pressure is, so the oil cooler is still cooling most of the oil going to the bearings, and the excess just goes straight back to the sump. Well maybe not all of it, since a portion gets directed back to the pump, so perhaps that "recycling" puts extra heat in the oil from the friction generated in the pumping, but is that really significant?


My point is that, yesterday, my stock pump ran out of oil pressure for the given conditions (so I had to increase oil viscosity to fix that), but most of the time, it has plenty of capacity (perhaps the engineers designed it for exactly the right capacity). The Melling has more capacity than is needed most of the time, but that comes in handy, occasionally, when the oil gets really hot and thin. It's the effect of that overcapacity that I'm wondering about now, and I'm beginning to think it's not all that bad, especially in hot climates and when running a multi-viscosity oil like 5W-40. thoughts?
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PostPosted: Thu Jul 19, 2018 9:39 am    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

you are blaming the pump but that is not where the fault lies. At 102F outside and 65 mph I would have been running 20W-50. The cause of the issue you describe is simple - the oil cooler can't keep up with the amount of heat being put into it. That is why some folks in hot climates run extended sumps - to allow a little extra heat to dissipate, or they run larger external oil coolers with fans and thermostats. The easiest work around is to run 20W-50 when it is hot like that. Doesn't make the oil any cooler - just gets less thin when it is that hot. VW's buses were never made for the way we use these - but you say - they were used in Africa etc., yes - at 35 MPH. If you drop to 40 - 45 mph your problems will go away too.
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PostPosted: Thu Jul 19, 2018 10:17 am    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

The tolerances of oil pressure switches is all over the board, I would first get a gauge and verify that what actual oil pressure you were running. Just replacing the oil pressure switch with a new one is another way to go. Verifying the lengths of you oil pressure relief springs is good to do as well. Weak springs that will let the oil bypass the cooler is not good. The oil pressure relief pistons can wear loose in their bores as well which will lead to an uncontrolled amount of your oil being bled off.
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PostPosted: Thu Jul 19, 2018 12:24 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

69BahamaYellow said:

.....but it got me thinking again about the Melling oil pump.


Quote:
Have others actually seen higher oil temps with the bigger Melling pumps / vs the stock type 4 pumps? I mean, under the same conditions (which is hard to control).


Yes...absolutely...and in Texas, Oklahoma and Kansas. I drove extensively in all of those states within the one year I had a Melling on my type 4 engine...yes...it absolutely CAN and in many cases will...bypass the oil cooler at highway rpms. Upwards to about 50 mph...it was probably bypassing a little but I still had significant pressure on the cooler circuit.

How do I know it was bypassing? because I got tired of seeing the smoking hot oil temps...pulled the 3/4 side tin off...put a spare piece of tin on it with two holes drilled right outside of the galley plugs on the oil cooler flange and plumbed in a gauge and idiot light for a month. Yes...it was absolutely bypassing.

Quote:
I understand all the fitment issues and leaking, and I get that the higher volume will open the bypass valve, if the pressure gets too high, and also bypass the oil cooler, but it's not like ALL the oil bypasses the cooler when that valve opens. I would think the oil pressure in the rest of the system stays at whatever the valve opening pressure is, so the oil cooler is still cooling most of the oil going to the bearings, and the excess just goes straight back to the sump.


No...thats not how oil coolers work...or radiators for that matter. The oil cooler cooling efficiency with low or no pressure oil....is orders of magnitude LESS...than an oil cooler with 40+ psi of pressure on that oil. And....low volume is low speed of oil movement...and low speed of oil movement = low volume passing through the cooler.

You need to understand....that the oil pressure relief circuit is simply two holes. One that is open to flow through the cooler....when the oils hot...and another holes that gets opened up when the oil is cold and thick. With both hole open...the pressure in that little two hole mixing chamber drops to really low...like about 15 psi. So though you still have oil flowing through the cooler at the same time its flowing back to the case......both are low pressure and the volume to either is half.



Quote:
My point is that, yesterday, my stock pump ran out of oil pressure for the given conditions (so I had to increase oil viscosity to fix that), but most of the time, it has plenty of capacity (perhaps the engineers designed it for exactly the right capacity).


I think that last part is not far off. They did a pretty damn good close job of design I think.

At what rpm was the oil light flickering? If this was at idle....much as I hate that....its common. What was your oil pressure at 1500, 2500 and 3500? As long as you have 10-12 psi----ish...at idle...its normal.

Quote:
The Melling has more capacity than is needed most of the time,


No...it doesn't. It has more capacity than is need ALL OF THE TIME. Its not just 6mm more of pump. There are lots of subtle details in the melling pump....and its damn efficient. Its output belies its difference in size. The efficiency of any of these pumps is not simply linear with each extra millimeter of gear.

Quote:
but that comes in handy, occasionally, when the oil gets really hot and thin. It's the effect of that overcapacity that I'm wondering about now, and I'm beginning to think it's not all that bad, especially in hot climates and when running a multi-viscosity oil like 5W-40. thoughts?


The friction and load from a larger pump does put some heat into the mix. I do not think its huge.....and living in Texas and Oklahoma....driving my type 3 cars, my type 4 cars...and yes even the 1971 bus with the hacked in 1.7L type 4 engine...that SGKent does not realize I owned and drove for two years Laughing ...and ...all of the type 4 buses I worked on for all of my friends living in that region....I have never "HAD" to run 20-50 oil.

102 F...is about normal for central Texas. Also 110+ is relatively normal in August. Thats just air temps. Temps up to 36" off the pavement in midday....will be 130+. Your oil will run hot. Even my waterpumper rabbit ran oil temps around Austin and Houston of 230-ish in the summer.

I would NOT run 5-40 though. 5W-40 is NOT just a "normal" 40 weight that also has some magical propensity to also flow well like a 5 weight at cold temps. The viscosity and flow modifiers do not work that way.

These type of oils ARE slightly thinner...ACTING.....because.....while the viscosity is tested the same and is the same between a 5/40 and a straight 40.. the actual oil FILM strength ...at maximum temps...of a 5w-40 versus a straight 40....are lower on the 5/40.
You do not get something for nothing. You cannot get the cold weather flow of a 5w....without sacrificing something from the 40w base oil. And that something is film strength. And...low film strength when the oil is hot is also what makes for the lowest pressure at idle.

The very best oil I ever found for driving in the Texas heat...highway miles...summer....was straight 40. Yes...back before synthetic oil was cheap.

The best oil and overall most available was Valvoline Super HPO -40. I ran the sae 30 in the winter.

If you are just going through Texas....check your oil pressures and see what you really have. It may be fine...or back down the speed a little....and just tough it out.
If you are going to be there for a while.....Walmart says they have Super HPO 40
https://www.walmart.com/ip/Valvoline-Super-Hpo-SAE...mp;veh=sem

If you are using synthetic...which I highly applaud....O-reilleys has Royal Purple SAE 40 full synthetic...and I think they also have some at Autozone.

By the way....straight 40 synthetics....are primarily two-stroke truck oil. Easiest place to find them are at truck dealers and truck stops. Ray
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PostPosted: Thu Jul 19, 2018 12:59 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

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There is also the late hydraulic where the excess dumps back to the oil pump inlet. I borrowed this from Richard Atwell's site. The issue going on in these threads is pretty simple - an ideal oil for a VW bus would be 10W-30, 10W-40 or SAE 30 if we could control engine temperatures - but we can't because the heat being generated exceeds the system capabilities. %W is too thin for most 70's cars. SAE 40 would be too heavy except on a worn out engine. BUT excess heat changes everything.
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PostPosted: Thu Jul 19, 2018 1:18 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

SGKent wrote:
you are blaming the pump but that is not where the fault lies. At 102F outside and 65 mph I would have been running 20W-50.



Agreed. I'm not going to swap out my OEM pump for a Melling, at this point, just to get a few more psi at idle. Thicker oil solves that problem, but I like running thinner oil (That's just my preference; don't want to get into an oil argument here). If my engine was still fully disassembled on my workbench, though, I think I'd go with the Melling. Ray showed us how to fix it's biggest shortcoming with the RTV trick, and I think it's volume provides a nice hedge against loose bearing tolerance (as they wear)
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PostPosted: Thu Jul 19, 2018 1:26 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

69BahamaYellow wrote:
SGKent wrote:
you are blaming the pump but that is not where the fault lies. At 102F outside and 65 mph I would have been running 20W-50.



Agreed. I'm not going to swap out my OEM pump for a Melling, at this point, just to get a few more psi at idle. Thicker oil solves that problem, but I like running thinner oil (That's just my preference; don't want to get into an oil argument here). If my engine was still fully disassembled on my workbench, though, I think I'd go with the Melling. Ray showed us how to fix it's biggest shortcoming with the RTV trick, and I think it's volume provides a nice hedge against loose bearing tolerance (as they wear)


Completely agree with you except that adding the Melling adds new layer of problems - what happens in winter when it is 15F outside and the SAE 30 / 10W-30, and large pump are pegging the pressure gauge well above 90 PSI? (Been there) The problem is that the oil cooling system in a VW is under designed for how we use it. That causes the oil to get so hot it thins out and pressure falls. One option you have is to add a low profile extended sump in summer. This is a very old and consistent problem that goes back 50 - 60 years.
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PostPosted: Thu Jul 19, 2018 1:28 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

raygreenwood wrote:
You need to understand....that the oil pressure relief circuit is simply two holes. One that is open to flow through the cooler....when the oils hot...and another holes that gets opened up when the oil is cold and thick. With both hole open...the pressure in that little two hole mixing chamber drops to really low...like about 15 psi. So though you still have oil flowing through the cooler at the same time its flowing back to the case......both are low pressure and the volume to either is half.



I have a GE Hydro case, so it only has 1 pressure relief valve. Maybe the earlier cases with 2 relief valves work the way you describe, but it appears to me that the single valve works just like pressing your finger over the end of a water pipe. It still holds pressure, even though it's leaking.
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PostPosted: Thu Jul 19, 2018 2:10 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

69BahamaYellow wrote:
raygreenwood wrote:
You need to understand....that the oil pressure relief circuit is simply two holes. One that is open to flow through the cooler....when the oils hot...and another holes that gets opened up when the oil is cold and thick. With both hole open...the pressure in that little two hole mixing chamber drops to really low...like about 15 psi. So though you still have oil flowing through the cooler at the same time its flowing back to the case......both are low pressure and the volume to either is half.



I have a GE Hydro case, so it only has 1 pressure relief valve. Maybe the earlier cases with 2 relief valves work the way you describe, but it appears to me that the single valve works just like pressing your finger over the end of a water pipe. It still holds pressure, even though it's leaking.


No....I'm not talking about the second relief valve...and its not a relief valve. Its a pressure control valve.

.....I am talking about the fact that the chamber for the oil pressure relief valive that the piston rides in....literally has two ports. The first being the hole that leads to the oil cooler. The second is the dump back to the case...which in your system dumps it back to the pump pickup.

So when the piston moves under pressure....it opens the relief port and.....high pressure becomes low pressure in the relief valve chamber and the cooler.

In short...when the oil is either thick and cold....or hot and thin but with excessive volume (which means excessive pressure) ....the relief piston moves down in the bore....allowing the oil pressure to access BOTH the relief valve groove and the oil cooler port.


Yes....it works like putting your finger over a water pipe....UNTIL the piston moves....and then it acts like you turned on a faucet in the feed pipe before your finger...or more accurately...poked a hole in the pipe. The pressure and volume at your finger is reduced.

Just understand.....in the relief valve bore....there IS a vent port for the oil to vent either to the case...or to the pump pickup like on your hydro model...and there IS still the port to the oil cooler.

When the piston moves...the port to the oil cooler does not magically close. So now you have TWO holes open for the oil to flow out of. This is what relieves the pressure...yes....but it does so by simultaneously reducing flow and pressure through the oil cooler....so the efficiency of the cooler drops DRASTICALLY .

The cooler only drops oil temps maybe a maximum of 20-25F on a good day. 15-20 F drop is average with average rpm and flow. And it only does that at pressure.

Take a look at the case cutaways of the pressure relief valve in this thread.

http://www.914world.com/bbs2/index.php?showtopic=236133

While this is the earlier type 4 case that vents oil to the sump instead of back to the oil pickup area like yours does...the venting process is the same.

If you can guarantee that the Melling will put out so much volume that it can BOTH vent ...and keep oil pressure to the cooler up...then you are golden. But you will have no assurance of that unless you test at the same galley points I did.

And...when I tested....I found that the cooler was being bypassed at highway speeds. And...the highway rpm at 70 mph in a 412 with a four speed....are lower by about 200 rpm than a bus.

But....I also did not have a late case. Between where your case vents to...and slight mods to the galley windows for your hydro lifters...you may just have better luck....so I would kind of like to see you try a Melling and set up the gauges and tell us how it works for you.

Ray
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PostPosted: Thu Jul 19, 2018 2:46 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Thumbs Up Ray Smile

More oil volume is not as simple a solution as it seems when the cause is oil too hot. It is a potential solution when the clearances down stream need more volume to maintain pressure. Wait until one has a high volume pump and winter arrives... .


The best solution on a daily driver in a hot climate is to add additional oil coolers, a fan, thermostat and valving. That however can introduce additional places to leak, and more things to fail.

Below is one of Aeromech's installs of such a cooler. Paul (Gears) added such a cooler to cool his transmission 4th gear. The 091 has a plastic caged needle bearing on the main shaft near 4th gear that melts when the bell housing end of the trans gets too hot. If the engine oil is too hot in a bus from driving too fast in 4th gear, especially on grades, so is the 4th gear bearing. There is a lot going on other than just reduced volume when these buses start to get too hot.
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PostPosted: Thu Jul 19, 2018 3:25 pm    Post subject: Re: Melling High Volume Oil Pump for Type 4 Motor Reply with quote

Ah Ha.....That cutaway in the link explains it much better than the diagram from the Bently manual. The pressure bypass port is necessary to get oil to the bearings while the oil is warming up (so the piston is acting like both a thermostat and a relief valve) There is still pressure in the cooler, but no flow through it while the relief piston is exposing the port to the oil galleys. If the pressure is still too high the piston opens further to expose the tapered notch to bleed off the excess pressure to the sump or back to the oil pump.


As the oil gets hot, it thins out and the piston closes the bypass port to the oil galleys, which makes oil flow through the cooler again. Now it makes sense to me why the pump should make only enough pressure to keep the cooler bypass port closed when the engine is hot; otherwise oil does not HAVE to go through the cooler and just keeps getting hotter, even though there is plenty of flow and pressure to the bearings. OK, now I'm glad I stuck with the OEM pump.


To use a high pressure oil pump, like the Melling, you should either force all the oil to go through an external oil cooler first, before it gets to the pressure relief/thermostat valve, or (better) figure a way to force any oil that is bypassed to the sump (or back to the pump) through an external oil cooler.
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