This may be a bit disturbing. I have now had multiple cases of replacement plastic fan blades that have broken. This is Moss Motors part number 434-332, replacement part for original 6-blade steel fan on 1962-1967 MGB. It is also sold as a "modern" replacement part for the MGA steel fan. It is "similar to" the OEM plastic fan for later model MGB (but may not be exactly the same structural configuration).

Date         Miles
05/06/15   445,038   Install plastic fan, Encinitas CA
07/16/15   455,667   Plastic fan failed 2-blades, Weaverville CA (10,630 mi)




08/15/15   458,719   Second new plastic fan installed, Hillsboro OR
04/12/16   479,540   Plastic fan broken blade, Matoon IL. (20,821 mi)

05/13/16   482,369   Plastic fan broken hub, Raleigh NC


The problem has been reported to the supplier. It is my best judgment as a mechanical engineer that the plastic used in these parts is a bad specification (no reinforcing fiber), and the ultimate solution would be to toss all remaining inventory and make new parts with better material. I will be waiting to hear the supplier's feedback, as they say they are looking into it immediately.

Meanwhile, I'm back to using a steel fan. Anyone running one of the replacement plastic fans may be well advised to check for stress cracks around the base of the blades occasionally, especially if it is approaching 10,000 miles in service.

On May 14, 2016, Tom Fant in Pinckney, Michigan, USA wrote:
"On 5/4/2016 I called Kelvin Dodd and reported a blade failure on the seven blade plastic fan. The fan was purchased 11/6/2012. The fan failed in April 2016 at 28,601 miles".

On Jul 21, 2016, David Jones in Hop Bottom, PA, USA wrote:
"One year to the day I ordered it! 11,238 miles before it broke doing high speed on the interstate. ... ---------------------------------->
I spoke with Moss this afternoon and they said send it back for credit".

Addendum, April 22. 2018: Apparently these fans were made from the wrong type plastic. Some time within the next two years Moss had corrected the problem, and the plastic fans are now listed as "Nylon".

Addendum, September 27, 2018:
On 9/25/2018, Max Heim (via Mgs mail list) wrote:
"A blade flew off the new Moss plastic fan .... and punctured the radiator. I made the mistake of trying to get it to the next exit ... which resulted in overheating and a blown head gasket. Total mileage to failure on this fan was 307 miles. --- Subsequent examination of the stub revealed an air pocket in the plastic right at the center of the base of the blade (manufacturing flaw). This model of fan was already out of production. Moss sent me a new fan ("new model" nylon 7-blade fan) and a new aluminum radiator (mine was irreparable)".

There have been more continuing reports of broken plastic fans. Apparently there were a lot of these sold before the change to nylon material, so there will be a lot of them installed and in use, likely for years to come. There may even be a few of them still in stock with other parts distributors. If you have a plastic fan purchased from Moss between 2012 and 2017, one originally listed as "plastic fan" before it was changed to "nylon fan", do regular checks for cracks at base of the blades. Failures have been reported in 10,000 to 28,000 mile usage. The 307 mile failure immediately above may have been for a different (one of a kind) "rare" manufacturing defect.

Addendum, October 27, 2022:
Someone or something reminded me that circumstances have changed and this page needs an update for my more recent experience with the Moss plastic fan. Story is that Moss finally saw the light, likely after multiple reports of more failed fans. I was told that the fans were always nylon, but the first batch may have been made from some sub-standard recycled material. Not sure if that is true or not, but the more recent product does seem to be better. If you had the early and later issue fans side by side you might see the difference. I think the later fan blades are slightly thicker at the root of the blades, making them stronger than the early issue parts.

I have recently installed a new issue Moss fan in my MGA, February 8, 2022 at 488,475 miles. Current miles is 504,921, so now 16,446 miles on the new fan. Still looking good, so I think the problem has been fixed. The remaining problem is that early issue and the newer parts are sold under the same part number. Some of the early issue faulty parts may still remain in inventory with some of the parts distributors, so if you buy one it would be nice if there was a way to recognize an older one to avoid it.

Okay I got it. Look at the back side of the fan. The first faulty one has a single thin wall center hub. The later better one has a double wall hub with gusset dividers all around (much stronger).

. The Moss nylon fan is 7-blade with asymmetrical spacing, so it runs quiet while moving more air than a standard steel fan (all good). I believe it is patterned after a later issue MGB nylon fan, so it may be larger diameter (slightly more than 10 inches). When I first installed one it touched the steel fan shroud I had been using since 1997, so I had to trim the shroud a bit for clearance. I don't know if this may be a problem with current issue plastic fan shrouds (or not).