Recommended transmission fluid for a 1950 MkVI?

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Hi All!

I’m a first time classic Bentley owner and obviously still have a lot to learn. I picked up a 1950 Mark VI at auction recently ( former owner was Peter Frank; he was a member here). My mechanic wants to get the transmission fluid changed before doing much else to it. He’s thinking that four quarts of Nitro 70 motor oil should do the trick. Just thought I’d run that by the experts here. While I’m out for it, what other types and brands of fluids should I pick up for it’s ongoing maintenance? I have the workshop handbook, but the oils and whatnot mentioned there are not available in the US, so I’m looking for modern substitutions. Your recommendations?

Thanks all!

John Murch · Posted: Sat Sep 25, 2021 7:03 pm Post subject:

Welcome to the club and I do hope you have a lot of enjoyment from your car.
Much more knowledgeable members will advise on oils (SAE EP 80/90 is I seem to recall the spec for gear boxes)
The manual for these cars can be found here
http://rrtechnical.info/mkvi/wshop.html

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Thanks so much for the warm welcome John! My vehicle came with a hard copy of the workshop manual and the “handbook for Bentley 4 1/4 litre”, but I’m still curious about what others may be using as preferred modern equivalents. Also, it appears that one of the previous owners coated the interior of the gas tank with a thick substance that’s now rather yellow. We’re they perhaps trying to protect it from ethanol? I was told that most Mark IV’s only take leaded gasoline, yes?

Christopher Carnley · Posted: Sun Sep 26, 2021 7:57 am Post subject:

Gearbox,.(transmission), SAE EP 80/90 or EP90. About 6 1/2 pints imperial

Rear axle, minimum SAE 80/90. Preferably straight EP140, if you can get it.

Engine: Multigrade 20/50 with ZDDP as it is a flat tappet engine.
Do you know if the oil filtration is by by-pass or full flow, as there were modifications?
The Hand Book has outdated lubrication information.
Shock dampers 20 grade, or if leaking 20/50.
Check the flexible pipe from the gearbox oil pump to the hydraulic ride control pipework for leaks, as this can empty the case and seize the gear train.
Expect heavy gas consumption.
The fuel tank will have been lined (Slosh) to seal the leaks in the rust holes above the holding straps.

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Thank you so much Christopher! I’m not sure about the fuel filtration; I’ll check on that this afternoon. It has yet to leave the mechanic’s garage since it was delivered over two weeks ago; mostly due to difficulties in getting the title transferred. For the curious, here’s the original auction listing. The previous owner had gotten a good jump on restoration, but sadly he passed away in a motorcycle accident earlier this year. I hope to complete what he began: https://rmsothebys.com/en/auctions/af21/auburn-fall/lots/r0358-1950-bentley-mk-vi-saloon/1151671

Martin Webster · Posted: Sun Sep 26, 2021 8:15 pm Post subject:

Welcome to the club.
You will have to ask your mechanic to drain the radiator and install a new top hose but the correct way around. The corrugated end of the hose should be attached to the radiator and not to the block. Even though you live in Florida, I would still recommend a 50% solution of old fashioned glycol based anti freeze in the coolant such as Bluecol if you can obtain it to inhibit the system.
Martin

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Thank you so much Robert, for the welcome and the information! I will pass that along.

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

If your fuel tank has been lined, expect problems from E10 - it will eat it and bits and pieces will block your fuel system. You need to have the liner removed and an ethanol safe coating used.

This from personal experience.

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Yikes! Thanks so much for the tip Dan! So you aren’t using leaded gas? Now I’m wondering how tricky it’ll be to remove that coating….

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

There is no need for leaded gas in that car. Pretty much any gas will do just fine. No need for special additives either.

You really need to strip that tank. It's a real pain to do, but much less so than rebuilding the entire fuel system and still having to do it.

Christopher Carnley · Posted: Wed Sep 29, 2021 9:22 am Post subject:

I was thinking, what a very well presented old car that you have bought, but they all come with a can of worms to contend with.

Although all the MK VI engines were built without hardened exhaust valve seats in the cylinder block, all factory reconditioned MK VI and R Type engines were from 1955 on, so modified.

It all depends if you wish to go to that expensive trouble.
Exhaust valve adjustment is done behind the two panels behind the exhaust pipe.

I also see on the picture attached, that the original, next to useless by-pass oil filter, is still in evidence.

The modification to the later full flow filter is an engine out job, and not a straight forward bolt on.
It is best to change the oil every 2000 miles max.

See the engine lubrication diagram in the Hand Book.

The sump (oil pan) takes 2 Imperial gallons,16 imp pints, and as it is a flat tappet engine, use one of the Mobil 1 oils,to your choice.

As to the petrol tank. There is a franchise operating out of Michigan called "Gas Tank Renu", and there is a branch at Garden City Georgia, at a firm called Chatham Radiators.

So rather than mess about with it, take it along or send it and have them give an opinion on it.

The two franchise outlets in the UK have given really good service.

The steering at slow speeds is difficult, so build up your shoulder muscles.

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Thank you so much for the information Christopher, I really appreciate it! I will look into those services. Once the gas/ petrol tank is recoated, what types of fuel do you recommend?

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Would it be less costly to replace the petrol tank than remove the coating and re-coat it? Just wondering if the secondary market has much to offer there. Thanks all!

Dan Suskin · Joined: 22 Feb 2011 Posts: 298 Location: Georgia, USA

It would be more economical to strip and coat the tank - a new one can be very expensive. But more than that - you need to asses whether it extend beyond the tank into the fuel supply lines (if the car runs well, it probably doesn't).

I think the advice to have it assessed properly before taking action is the best course. Given how long E10 has been used in the US it is possible that the coating you have is in fact ethanol resistant.

John Murch · Posted: Thu Oct 07, 2021 10:19 am Post subject:

I see that there is a Mk VI fuel tank for sale in the current “Advertiser”. Of course it may well be in a worse state than your current one.

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

Thanks so much for the heads up John! Sorry that I missed the notification for your reply. I appreciate it!

So far the restoration is going fairly smoothly, but we haven’t addressed the gas tank yet.

JGwynne · Joined: 20 Sep 2021 Posts: 21 Location: Florida, USA

And thanks for the info Dan! I just found a Bentley certified mechanic not far from me here who has worked on many classic and vintage models. Hopefully he’ll be able to make that assessment!