Description

Bentley MARK VI Service Manual

If you’re wrenching on a Bentley MARK VI Service Manual from the postwar era, you already know the drill—factory documentation is the only thing that keeps you from chasing ghosts in the cooling system. This 43-page binder isn’t a full shop manual; it’s a collection of official service bulletins that Bentley Motors (1931) Ltd. sent out to dealers and service depots. I’ve seen guys burn three hours trying to route heater hoses on a Mk.VI because they relied on a reprint that skipped the restrictor disc note. Don’t be that guy.

What’s Inside the Bentley MARK VI Service Manual

You get three service bulletins in this 43-page document. First is Bulletin BB-8 covering the car heater system—specifically a restrictor disc (Part No. RE.5767) silver-soldered into the feed pipe to prevent matrix damage from excessive water pressure. Page 1 shows the exact position of that disc and the fixing method. Next is Bulletin BB-11 about the radiator steam valve. The factory originally pressurized the coolant to 4 lbs per sq.in. Then they decided to run it at atmospheric pressure and ordered the ball and spring removed from the valve housing. Page 2 tells you to unscrew the hexagon plug on the header tank, pull the spring and ball, and dab white paint on the steam pipe to mark the change. Last is Bulletin BB-88 for fitting an additional interior car heater behind the facia panel with improved demisting and defrosting ducts. That’s the meat of it—no fluff, no generic reprint garbage.

43 Pages of Factory Service Bulletins – Why Size Matters

You might think 43 pages is thin for a service manual. For a 1940s Bentley, it’s exactly what you need. These bulletins target the specific failure points that Bentley engineers found in the field. The restrictor disc fix alone saved a lot of heater cores from splitting open. I’ve had a customer bring in a Mk.VI with a overheated cabin and steam pissing out under the dash. Without the bulletin, I’d have replaced the matrix blindly. With the factory procedure, I pulled the pipe, found the disc was missing, installed RE.5767, and buttoned it up. One hour, not five. That’s the difference between OEM data and aftermarket guesses. The Bentley Mark VI 1947 Service Manual is a related supplement that covers other early updates. If you need the later heater kit installation, check the Bentley Mark VI Service Manual Bulletin BB-13 for additional details. And for post‑1949 production changes, the Bentley Mark VI 1949 Service Bulletin fills in the gaps.

Car Heater System: The Restrictor Disc Fix

Bulletin BB-8 is a one‑page drawing with a simple principle: control flow to stop pressure buildup. The restrictor disc is silver‑soldered into the feed pipe from the cylinder head. The drawing on page 1 shows exactly where. Part number RE.5767. Actual size is printed on the page so you can verify it with a caliper. If you skip this step and just plumb in a modern heater valve, you risk blowing out the original matrix. I’ve seen it. The matrix is NLA—so you save it or you fabricate something that never fits right. This bulletin is your insurance. The Automotive Industry Overview shows how manufacturers evolved cooling system designs, but for a Bentley Mk.VI you stick with the factory bulletin.

Radiator Steam Valve Modification – BB-11

Bulletin BB-11 is a two‑pager that tells every retailer to remove the ball and spring from the steam valve housing. The coolant system originally pressurized to 4 psi. Bentley decided atmospheric pressure was safer. The procedure: unscrew the hexagon plug on top of the header tank where the steam pipe attaches, remove the ball and spring, then paint a white dot on the steam pipe near the chamber. You then notify the London Service Depot with chassis numbers. That’s it. No guessing, no aftermarket pressure caps. If you’re restoring a Mk.VI and wonder why the system doesn’t hold pressure, this is why. The manual doesn’t include torque specs for the hex plug—but the bulletin assumes you know hand‑tight is fine. Use a thread sealant if the plug leaks. Page 2 of the original bulletin even has a note: “ALL COMMUNICATIONS SHOULD BE ADDRESSED TO BENTLEY MOTORS (1931) LTD.” This is the real deal.

Is This Manual for You?

If you own a Bentley MARK VI Standard Saloon and plan to drive it in cold weather, yes. If you’re a restorer trying to keep the original heater system intact, yes. If you’re a shop taking on a Mk.VI that has overheating issues or a heater that doesn’t blow hot air, this saves you the trial‑and‑error. The bulletins are short, direct, and factory‑approved. You won’t find step‑by‑step removal of the dashboard or seat—that’s not the point. The point is exactly which part to change and why. The Automotive Industry Overview context matters because these bulletins reflect a time when manufacturers actively communicated updates. No tech hotline, no online portal—just paper bulletins sent to dealers. This manual preserves that knowledge.

Why OEM Documentation Beats Aftermarket Reprints

Aftermarket “service manuals” for the Mk.VI often cobble together speculative wiring diagrams and mis‑typed part numbers. I’ve seen one that listed the restrictor disc as a “water control valve” and never mentioned silver soldering. That’s how you blow a matrix. This is an authentic scan of an original Bentley Motors service bulletin, not a third‑party rewrite. The part numbers match the factory parts list. The dimensions are as‑built. The instructions use terms like “silver soldering” and “hexagon plug” because that’s what the engineers wrote. You pay for accuracy, not fluff. 43 pages, no filler.

Does this manual cover full engine or chassis repair?

No. This is a 43-page service bulletin collection focused on heater and cooling system modifications, not a complete workshop manual.

What is the restrictor disc part number and how is it installed?

Part No. RE.5767. The disc is silver‑soldered into the heater feed pipe at the location shown on page 1 of the manual. The bulletin includes an actual‑size drawing so you can confirm you have the correct disc. Silver soldering must be done carefully to avoid restricting flow; the disc is placed in the feed line from the cylinder head to the matrix. If you don’t have access to silver soldering, you can braze it, but the factory specified silver solder for corrosion resistance. Once installed, the disc reduces flow enough to keep internal pressure below the matrix burst point. No other modifications are needed. The bulletin states that this was embodied during assembly on all cars except a small number—retailers were notified individually. If your Mk.VI still has the original heater and you’re unsure whether the disc is present, pull the feed pipe and look. The drawing on page 1 shows the exact orientation.

You’re staring at a car that’s 70+ years old. The factory that built it sent out these bulletins to keep it running. Don’t rely on internet rumors or photocopied reprints. Access the Factory Manual now and get the exact instructions Bentley intended for its service network.