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MG MGA - Overheating

Hi, my name is Agustín Morales and I live in Bogotá, Colombia. I bought recently a very nice MGA. From the first moment I had vapor lock issues when the temperature aproached the 210-220 F. Then I installed an electric fun and I operate it manually stabilazing temperature in 190F, and this seemed to solve the vapor lock issues. Any way I would like to operate my car at 190 F WITHOUT using the electric fun, leaving it only for some emmergency. Any suggestion? Which should be best thermostat for my car? In Bogotá we have 65-70F all the year; we don't have seasons because we are located near the Ecuador line.
Best regards!
Agustín Morales
Agustín Morales

Agustin

Welcome to the board. The reasons for the overheating can be various, even down to the accuracy of ignition timing. However, on the coolant side a good starting point is to make sure you have good water circulation. For example, is the radiator clogged up with sediment? It may be a good idea to drain the system, remove the radiator and flush through. Refit and see if that has made any difference.

Do you know the car's history? For example do you know if the radiator has its original core? Many modern style cores are unsuitable for the MGA. It is important to get as close to the original as possible.

My radiator core is modern but very close to the original specification and keeps the engine (the MGB 1800 variant) at 175.

Steve
Steve Gyles

The first thing to do is check that you have the correct radiator cap, as many are too short, which allows water to escape and prevents the system pressurizing, which means the car runs too hot. The core ct cap should be 1 1/4 inch between the rubber washer and the bottom of the cap.

Also, is the fan mounted correctly, with the concave side of the blade at the back.

Then you need to do as Steve says and flush not only the radiator, but also the engine out. I have noticed considerable running temperature differences behind the same radiator between an old engine which is gummed up with sediment, and a new engine that has been caustically cleaned. With those ambient temperatures it shouldn't run that hot if everything is correct.

If the car has a brand new radiator, I would also suspect that. I have had them cause serious overheating problems fresh out of the packaging.

My bet is on the radiator cap, it's the first thing I check when people complain of overheating. In many cases, just topping up and fitting a correct cap solves the issue permanently.
dominic clancy

Agustin

Steve, and Dominic, are right and the main point is the radiator itself. I understand that some modern replacements are absolutely dire in an MGA. Good original ones worked well so you shouldn't need electric fans. There is almost no chance you have an original one never mind a good one. I have had mine re-cored over this winter and on my first run yesterday it seems to have dropped my temp by 10F. This is not quite down to Steve's figure but there again how accurate/consistent are the gauges? Incidentally my radiator was an early recore probably dating from late 60s so wasn't bad in its time.

Mine is also an MGB 1800 engine which presumably generate more heat. It is difficult to know where to get a decent replacement/rebuild from but on Steve's earlier advice I went to Bob West who as a top restorer, rather than just parts supplier, knows what works. Within UK his turnaround is about 2 weeks but he does prefer/only do rebuilds. Incidentally Bob insisted on giving me a cap so he was sure I was using the correct one (which I was actually as it happens).

Paul



Paul Dean

Two issues here.

The first is vapour lock that is primarily caused by high engine bay temperatures and also fuel used.

The second is the high running temperature that has been partly addressed above.

Other things to check are that the two air pipes are fitted in front of the radiator cowl and that the seal is fitted to the bonnet above the radiator. These all prevent hot air recirculating through the radiator.

A fan shroud can also be a worthwhile addition.

For the vapour lock the best solution appears to be a bilge blower inside the LHS air pipe/rad cowl.

I think all of these items are covered on Barney's website: www.mgaguru.com
Neil MG

I find this thread interesting as I experienced over heating at end of last summer whilst driving at 40 - 50 mph. In the past it only happened in traffic and resolved itself as soon as I picked up speed.
I am about to flush radiator & engine, and change the thermostat in the hope that will sort it.
I would be interested to hear any views on whether the felt that is supposed to be stuck to bonnet above radiator is worthwhile. My car doesnt have one. I believe it prevents hot air escaping from engine bay and recirculating back in front of radiator.
Also any tips on magic additives to use for flushing, or is simple water just as good?

Thanks, Graham
g Victors


Agustin,

No one mentioned or asked if you have the heat shield installed between the carbs and the exhaust manifold.

Ray
Ray Ammeter

To answer your questions Graham; it seems that there are many cars that run perfectly well without the bonnet seal (and even the air ducts). But perhaps those cars are not in condition or situation where they are close to overheating in any case. In other words I think the difference is marginal.

Regarding flushing you could use Radflush, or other agents to help. Certainly they will have more effect than just water, which has to be used afterwards in any case. Even using the very best flushing agent will have little effect on any serious deposits in the block and radiator if they are already established. But so long as there are no serious overheating problems it can only help IMHO.
Neil MG

Agustin

Steve is right and the main point is the radiator itself. I understand that some modern replacements are absolutely dire in an MGA. Good original ones worked well so you shouldn't need electric fans. There is almost no chance you have an original one never mind a good one. I have had mine re-cored over this winter and on my first run yesterday it seems to have dropped my temp by 10F. This is not quite down to Steve's figure but there again how accurate/consistent are the gauges? Incidentally my radiator was an early recore probably dating from late 60s so wasn't bad in its time.

Mine is also an MGB 1800 engine which presumably generate more heat. It is difficult to know where to get a decent replacement/rebuild from but on Steve's earlier advice I went to Bob West who as a top restorer, rather than just parts supplier, knows what works. Within UK his turnaround is about 2 weeks but he does prefer/only do rebuilds.

Paul



Paul Dean

Paul

You and others know about me and my radiator thing. I have 2 anecdotes to support my theories. The first was on the MGA 50th anniversary run from Abingdon to Le Mans. At Artagnan the 20 plus cars did an official drive in convoy through the town. Some cars overheated, some did not. Back at the overnight garage Bob West spent quite some time looking at those cars while we all looked over his shoulder. Virtually every overheater had a replacement (non standard) radiator core. The rest of us were close to original. 20 cars, identical conditions. It was an excellent opportunity to make a valid comparison.

The second anecdote was back home. My neighbour up in the Preston area had an overheating 1500. He had tried everything mentioned in the above posts, including the electric fan and oil cooler. One day when I had my 1800 out for a repaint I lent him my radiator. Instant success. His temps were down by about 20 degrees. Next day off he went to Bob West. Also, off came the fan and oil cooler. Never had a problem since.

Steve

PS. calibrated my gauge with the wife's marmalade thermometer, so I know it's pretty accurate (the marmalade sets ok!)
Steve Gyles

Running a supercharged engine with an original spec core is also absolutely fine and causes no overheating at all. I installed a supercharger in another care,p and fitted a brand new Moss radiator at the same time. The result was terrible overheating. How did we solve it? We installed an original radiator that the owner had bought on eBay for ten Euros.... Instantly resolved the problem without changing anything else. don't use a modern radiator unless you absolutely have to, get an original spec core and all will be fine.
dominic clancy

This thread was discussed between 07/04/2015 and 08/04/2015

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