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MG MGB Technical - Top radiator hose cut by fan!

I changed the hoses on my '68 roadster recently and took it out for a run in rediness to change the oil. I had to call at a motor factors to get some 24V bulbs for my garage door opener. When I left I noted an anti-freeze smell and found that the top hose had seemingly split. Fortunately the motor factors had a hose I could adapt as a replacement and I found that the corrugated hose had been cut by the fan blade and not split. This hose was from the MGOC and was not Kevlar reinforced so was a lot more flexible than the one I took off. I can't imagine how it got cut as the fan blade is at least an inch forward of the hose. Has anyone else seen this? Either the engine has to move forward an inch or the hose has to be compressed for it to flex forward by that amount. I've since put the original back on.
Steve Church

Is your left hand motor mount in good shape? If not, this could explain the failure. Having owned the same '67B, for over 40 years, I've never encountered this problem and I removed my stay rod some 25 years ago. RAY
rjm RAY

Both engine mounts are new (500 miles ago).
Steve Church


Just been out to look at mine - original style reinforced corrugated hose. Can't see how it could happen in operation, unless you had excessive length in your hose and (being un-reinforced)it danced about under water pressure variations through stat settings.

At the stat housing end the relative hose and fan positions are fixed. If my engine came forward 1" it would be through the radiator and the hose would pass under the lip of the shroud ledge.

A photo (in situ, staged given replacement) would help, but I wonder, pre-existing cut or something done installing?

Roger T

Definitely cut when in situ as the fan blade tips have rubber deposits on them and the hose has been coloured yellow by the paint from the fan blade. I can't figure it out either but I shan't be fitting a really flexible hose again.
Steve Church


In case it helps, photo of mine. There is not a lot of 'elasticity' in the corrugations on mine - firm to install, requires a hefty manual compression to get it over the second mounting point. A good rugged hose, no likelihood of 'dancing' around underway.


Roger T

Only two possibilities:
Hose swells under pressure - check the cap for pressure relief problems, and check the hose visually when you get the engine hot.
Fan is flexing/cracked/loose etc. Could be a real disaster, unto death - it has happened. Check very carefully.

FR Millmore

Steve - check those engine mountings again, plus the rear mounts - especially look for any retaining bolts not tightened up.

It is not the engine moving forward - this would take the fan away from the hose, but rather it is the engine moving up and back a bit that puts the fan on a collision course with the hose. It only needs a brief torque kick and the fan will pass the hose several sweeps, and as you know, the B series engine was never designed with new fangled words like 'smooth' and 'balance' in mind!

If it persists or it is a concern, then a short torque damper as in photo might help.

Hal Adams

I have experienced this problem after I changed the timing cover oil seal on my car, as I recall it was the bottom hose which was court by the three blade cooling fan, but I had to put it down to my own careless fitting of the bottom hose which was twisted slightly into the wrong plane, I ended up fitting a new hose.

Regards Patrick
P.T. Tighe

This thread was discussed between 16/10/2012 and 17/10/2012

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