Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Over winter servicing

While my M3W is in its winter storage at a local classic car garage, I am going to get them to change the Crankshaft Position Sensor to one of Andy Warren's ones. I have translated the instructions into French using Ai, gone through it and corrected some of the howling errors, like calling a crankshaft an operating handle etc (Manivelle when it should be Villebrequin). I am also going to get them to replace the brake fluid and bleed the brakes (purger les freins). My question to the forum is what is the best fluid? DOT 4 or purple DOT 5 silicone fluid? I would guess DOT4 but not sure.

Wilson

DOT 4 is ideal.
DOT 5.1 is also very good but definitely not the silicone DOT 5.
The silicone fluid doesn't mix well with normal fluids and would almost certainly rot at least some of the seals in the system.

Dot 5 is not compatible with Dot 4. It will destroy your brakes.
Even in my race cars I used DOT 4. No need to grab 5.1.

I just experienced a clutch failure and found out this was because the clutch master cylinder was never flushed out during fluid changes. My M3W has been serviced by a non-Morgan service agent, and I always asked for my brake fluid to be flushed out and changed thinking that all of the fluid would be changed because the clutch and brake fluid use a common reservoir. When my clutch failed, I surmised it was the master cylinder and ordered a new one. When it was replaced, black sludge was found in the old master cylinder, and we realized that it had never been flushed out. So my point is when you ask for a brake fluid change , make sure they flush out the clutch master cylinder and clutch related tubing at the same time. I never specifically requested that thinking all of the fluid in the clutch and brake system would be flushed out, but it wasn’t.

Use Dot 4.

I don't want to hijack this thread but Sportster's experience regarding flushing the clutch slave cylinder fluid is well taken. Any tips or direction to a blog on the procedure? (I did a quick search without success). )-: FYI- For the brakes a fresh can or two of DOT 4 is all you need. Suck the old fluid out of the reservoir (wifes turkey baster works best- just not the day before Thanksgiving). Fill with fresh fluid and bleed away (while keeping it topped off). Also I had my rear wheel brake cylinder freeze up last season. I had not bled the brakes since new in 2016.

I had the clutch master cylinder changed last year by M3W services in France. I thought the clutch hydraulics had failed but it was actually a broken finger on the clutch cover plate, that was the problem. The engine was coming out anyway to fit a Bleazey compensator, so not a lot of additional work.

Wilson

So to clarify, when you replace the brake/clutch fluid in the reservoir and bleed the brake lines the remaining fluid in the clutch master cylinder, the clutch slave cylinder, and clutch lines is not being replaced. That side has to be bled out as well. I believe the clutch line bleeding valve is accessible under the engine oil reservoir under the bonnet. Beyond that I’ve never done it, my local service tech did this for me. After replacing my clutch master cylinder and replacing the fluid, my clutch works great.

The reason I bring this up during a discussion of bleeding the brakes is because both the clutch and brake lines share the same reservoir. Certainly a certified Morgan service technician will know to flush out both the brake and clutch side at the same time, but a non Morgan trained service tech might not know that, as a result my failure of the clutch master cylinder. So for those people doing this themselves or using a non Morgan service tech now you know.

Just to clarify - not all m3w's share a common reservoir. Early cars had a 3 reservoir set up.

The reason you had black sludge in the master cylinder was because the cylinder seals had failed - nothing to do with flushing out the fluid correctly. The master cylinder would have failed regardless.

Wilson - Dot 4 is fine.

Thanks for your input.

If your M3W doesn’t share a common reservoir, then what I am pointing out doesn’t apply to you.

Still an important issue, if you don’t make a conscious effort to flush out the clutch side with a common reservoir system, then just bleeding the brakes isn’t going to accomplish that. The fluid used in our brake/clutch is hydroscopic so if you never change it, that fluid is going to absorb water and cause internal corrosion and may damage the master cylinder. Never changing a hydroscopic fluid in a master cylinder whether it’s a clutch master cylinder or brake master cylinder can’t be good.

Even more expensive, hygroscopic fluid can damage the clutch slave cylinder which is a lot more work to replace than the master cylinder, as it is integral with the release bearing and requires engine removal to replace. Luckily mine was all replaced along with clutch and master cylinder just last year so no need to worry about it for the present.

Wilson