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MG MGB Technical - Figure this one out

Here's one for the "scratch your head" file I was out last evening enjoying a nice little drive with the hood down and everything was great when I went over a large pot hole in the motorway and instantly I hear a scrapping from under the bonnet, I pulled over and popped the bonnet to investagate and found that two of my fan blades has been bent forward almost 90 degrees and boring a large hole in the back of my Radi. and I was loosing fluid quickly from the hole not being but a few blocks from my home I decided that I had already done the damage so I got in and drove the B the rest of the way home spewing anti-freeze everywhere. Here the wierd part after investagating the motor area after cooling down looking for a broken motor mounts or loose radi. mounting hardwere I discovered EVERYTHING was tight (by hand) If everything is tight and not broken then how can the fan travel into the radi. or the reserverse the radi. travel back into the fan? These are fixed items and should not be able to move. I know the motor is designed to move side to side but front to aft. I had planning on removing the radi. for recoring this winter, it just moved my time table up a bit and I have a number of other 5 blade fans laying around so no loss there.
Thanks
Jeremiah Randolph

If both engine and radiator are solid, then could it be that a stone was thrown up and the fan blades caught it ?
Miles Banister

Perhaps the bond between the rubber and the steel plates of the motor mount failed. Bolts would still be tight and all would appear ok. You night put a floor jack under the engine and raise it slightly to check.
Good luck,
Dennis
D F Sexton

Throw away that awful water pump/radiator/ never cools enough, ruining thing!
Installl a good electric fan!

Safety Fast
Dwight

Dwight

If the fan blades were bent towards the radiator then I can't see how it could have been either the motor moving forward or the radiator moving back. I would imagine that if that indeed did happen then the blades would have bent towards the engine on impact. It sounds like something struck the blades from behind and pushed them forward causing them to shred the radiator. Is there anything else loose under the hood such as the alternator, air pump, etc? Or it could be as Miles said an object was thrown into the engine bay and caused the damage.
Lewis

Sounds like the impact caused a forward shift of the engine (so check those mounts), tipping the fan blades into the radiator. Two blades caught the radiator and were bent, and pulled into the 90-degree position as the engine tipped back after impact.

Once past the point of impact, gravity took over and the engine settled back to its normal position. Things would look good, and unless you were extraordinarily strong, you wouldn't be able to lift the engine by hand. To test the theory do the "lift test" suggested above.

BTW - electric fans have advantages, but cooling per se isn't one of them. Engine driven fans use up 2-3 hp off the crank, while electric fans are fractional HP motors, and do not move near as much air. They have advantages, though, as auxiliary fans, and at low speeds, such as idle, or reducing the heat sink effect by operating after the engine is turned off. I think MG moved to electric driven fans in the later cars because 1) they needed to get every HP they could get back from the emissionized engine, and 2) with the later, high capacity radiator, they thought they could get away with it.
John Z

Had'ent thought about an outside object entering the motor area but it makes sence. The direction of the blades throw me as well I will try the jacking thing today and see if anything moves out of place but I have my doughts as this is a VERY clean preserved car and I am anal about checking for loose pieces and would have noticed any thing wrong before now
Thanks
Jeremiah Randolph

Not sure of the year of your B, but up to about 74 the motor mounts had steel plates bent 90 degrees which kept the engine from moving for and aft. Often these are left out when engine work is done. As well there is a threaded rod on the transmission mount again to stop for and aft movement.

HTH

Ron
Ron Smith

This was atually a common occurance back when the roads were well populated with B's. Railroad tracks/potholes would cause a shift twist/that would cause the fan blade to catch the lower edge of the radiator, twisting the blade into the core. The other thing that would happen, and sometimes in tandem for the maximum pucker factor, is that the hood (bonnet) would release its main catch, and as so many secondary catches were bent/misadjusted the hood (bonnet) would come flying up, catch the wind and slam back into the windshield. Those L shaped brackets mentioned above were left out by even otherwise conscientious mechanics as they just didn't see how a motor could move forward far enough to cause a problem. The clearances/adjustments were on a long list of things to check when aquiring another B as even paid professional mechanics just didn't understand/get these greatest of the British cars and just wanted to get them done and out of the door.
Rick

You might have had a foreign object eg. a wrench or screwdriver lodged somewhere in the engine bay which became dislodged when the car went over the pot hole. I remember a 1/2"-9/16" openender, which I'd used to tighten a fan belt a few days earlier made a terrible mess of my radiator & fan. Barrie E
Barrie Egerton

I vote with Ron...transmission mount.
Paul Hanley

Second the transmission mount vote. Whilst not a B, my midget did the same whilst Auto Testing. A rapid stop astride a line then a large amount of steam and that sickening smell of Anti-freeze. The Engine mounts where fine, the transmission mounts on further invesitgation failed.

Hope you get it sorted, I'm now off to check my B for those angled brackets.
A I McGee

The year is 1970 and this car is as close to it appeared in 1970 as I can get it so there is no Stay Rod on the trans mount. My research on this year has found that BL/MG had discontinued this rod prior to 1970 so no rod on this car. I will check the motor and trans. mounts and pull the radi and fan blade today Thanks
Jeremiah Randolph

I have a 1970, and can attest that there is no stay rod, but it does have the L-Shaped brackets on the front engine mounts. These brackets are the only system to keep the engine from moving forward into the radiator. If you don't have any, I'd suggest buying some, Moss list these as 'Recoil Bracket' Part # 413-075, $12.95 (2 req'd.). Cheap insurance for the radiator, in my opinion.
Mark B.

I have a 70B as well. They did change things around several times, the 70 did not have the stay rod on the tranny. It did not reappear until 74 or so. It should have the motor mount restrictors however. One points fore, the other aft. When I went through the B several years ago I found that the tranny mounts had been oil soaked for years, and they were soft and basically falling apart. They are a pain to replace with motor/tranny in the car, but it can be done.

Safety Fast

Ron
Ron Smith

Here is my guess what may have happend. Your fan is on backwards, the air flow would still be correct but the leading edge of the fan has notches about 3/8 x 1 to clear the bottom of the radiator tank.

This happened on my 71 with new motor/trans mounts after a rebuild. I had a bit better luck as the fan only grazed the fins but put a good size nick in the bottom tank. I was able to repair the nick with JB-Weld and remove the fan completely to get back home.

The electric fan I had on also helped to keep the car from overheating, but still was not enough as the needle was getting to close to the H for comfort.

Barry
Barry Glass

I think it's your stayrod. It's what keeps the motor from moving front & rear.
CDD Dewey

I had this happen last year after crossing the RR Tracks of Doom. The motor does not have to shift forward very much for the fan to just catch the upper edge of the lower radiator tank. This bends the blades and puts that perfect circle on the radiator. My 73 had new motor and tranny mounts and the bracket on the motor mounts but did not have the stay rod. I switched to the plastic fan, no difference in cooling or temp, and plan on installing the stay rod at some point. If the motor is shaken violently enough, it can indeed put just enough of the fan into the radiator to mess things up even with new mounts.
Wray

It was said: "BTW - electric fans have advantages, but cooling per se isn't one of them. Engine driven fans use up 2-3 hp off the crank, while electric fans are fractional HP motors, and do not move near as much air."

Not true as I've been using an electric puller fan as my primary and only fan for many years.

Spal makes a great fan that is more than up to the task of cooling an engine.
Mike MaGee

This thread was discussed between 09/09/2005 and 12/09/2005

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