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MG MGA - Thanks-overheating

Thanks for the suggestions from all. Finally after trying to deal with over heating problems, they are fixed. I kept looking at the engine and the fan was backwards. My now ex -mechanic insisted it wasn't and refused to fix it.( He originally turned it around when replacing the radiator, which had to be recored because he didn't put the spacers in the first time and ripped a whole in the brand new one). I had to do some modification to the radiator panel to make the radiator fit. But alas...after a few hours I had the fan turned around.

The temp was 15 degrees cooler on the test ride. Barely hit 190 degrees going up the longest stretch of hill on the highway doing 65mph.
The clearance is about 1/4" from the radiator; tomorrow I get larger spacers to move the radiator a little more forward.

Cheers,
Merl
60 MGA 1600
Merl

Merl

Two possibilities for the small clearance. Do you have the thick rubber packing strips between the radiator and the mounting? Alternatively you may have one of the water pump variants (possibly off an 1800) with a long drive shaft. I have a short shaft pump on my engine, giving a full inch (2.5cm) clearance between the front of the blades and the radiator. The spare pump I have on the workbench has a shaft 1.5cm longer. This could account for your clearance of only about 1/4".

Steve
Steve Gyles

What I can not understand is if you turn the fan around the airflow is still the same? Also the fan should have no effect when the car is moving forward at reasonable speed. Airflow through the radiator is far more at speed than the fan could ever deliver. Was the recored radiator the real fix of the overheating problem?
Bob (robert)

The fan is cambered like a propeller (concave on the backside) the amount of air moved by a fan backwards would be greatly diminished. The design of the propeller by the Wright brothers was one of the most significant advances they made. Yes fan shape and direction makes a great difference. A backwards fan would also limit airflow at speed. A slowly turning prop on an airplane creates more drag than a stopped one. A fan shroud would also help. Moving the fan away from the radiator core without using a fan shroud will reduce the fans efficiency.
R J Brown

Merl,
Hope you find a better mechanic. Perhaps yourself. There are plenty of "professional" mechanics for whom half-a**ed is good enough. Check around amongst your other britcar buddies in your area, they will likely gravitate to one who is good. And if there isn't any alternative on the open market, you can always get a shop manual and learn the trade. These cars are simple enough that even I can keep them running. Cheers!
Bob Muenchausen

I don't recomend smoking, but a quick test is to light up a cigerette and put it in front of the radiator. If the fan is in properly, it will suck in the smoke of the cig. If it blows it away from the radiator, you have your fan on wrong.!!!
JEFF BECKER

Jeff

You have it wrong. Putting the fan on the other way round does not reverse the flow, it merely affects the efficiency of the blades - as discussed in previous posts.

Steve
Steve Gyles

R J, I accept the fan will be a little more efficient fitted the correct way but it would not cause a vehicle to overheat when travelling forward at reasonable speed. I am curious what was done in what sequence to Merl's car that has caused it to now not overheat.
On the other hand we keep hearing stories of incompetent mechanics, a mechanic that can not logically understand which way around the fan should be fixed for greatest efficiency ought to be put to work pulling a plough and give the horse the spanner.
Bob (robert)

Robert,
Originally I took the car in because it had been parked in a garage for three years, was my fathers.I just wanted hin to check it out. I told him to replace the filters, put new fliuds in everything and flush the engine/radiator. I had it flat bedded to the shop, since I didn't want to start it without someone looking at it first. The first place charged the battery and it started, so he filled the fluids and checked the plugs. Also he replaced the rear brake cylinders and the tie rod ends. It overheated on the way home from the shop. The next place replaced the radiator, master cylinder, rear brake drums, put on the stock air filters and then made sure the timing and mixture was ok.

The car was good for the half day, and then started to run up to 200-212 on the freeway driving on a flat stretch of road. While checking things on the car I noticed the fan was on backwards, and that was corroborated by another mechanic. Funny I had to hold up a fan not on the car to show him it was on the wrong way.

Yesterday I drove around in the hot northern California weather around 80 for a test drive after I switched the fan. Cool engine temp. All I did was remove the radiator, spin the fan and replace the radiator, topped off the coolant and drove. After making sure the fan would clear the radiator of course. This morning it was a mild CA 55, and I noticed the car barley made it to 170 degrees.

Don't know what or why, but I guess I'm going to start doing some of the work on the car. I just want to drive it around on Saturdays and have fun with the wife and kids.

Cheers,
Merl
Merl

If the fan is backwards it will restrict the flow even at high speed.The difference is not "little". If you use an electic fan that has too small of a capacity it to can restrict flow. The moving fan limits the air flow to the capacity of the fan. The thought of adding a small helper fan to the front of the radiator actually limits the air flow. If you are going electric get a sufficient fan, they are rated in CFM or cubit feet per minute, and remove the orig fan. The spinning disc of a fan sets the maximum rate at which it allows air through. Jeff, Steve is right reversing the fan doesn't reverse flow. A stopped fan lets more air through if the car speed is high enough. Think of a spinning fan as an airflow regulator not a helper.
R J Brown

This thread was discussed between 04/09/2005 and 05/09/2005

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