Bubbling sound from radiator

[JeffMoore64]

Greeting's,
Took my mgtc for a spin and noticed that the radiator sounded like it was bubbling. Is that normal?
Jeff

[Steve Simmons]

Most likely boiling coolant. If you have a temperature gauge fitted, what does it read? Has it been tested for accuracy? Alternately, place a candy thermometer through the radiator cap, or an IR thermometer on the top tank of the radiator. If you're at high altitude, remember that water will boil at less than 100-degrees.

[frenchblatter]

I've got the same problem. I've ordered a petronix ignition module as I can't get the timig correct with my strobe.

I'll let you know how it goes.

By the way, I know it's ignition related as it was boiling fiercly before I advanced the distributor. But now I won't advance any furher and reads about 30 degrre BTDC at tickover.

[Duncan M]

Jeff-
Overheating is sometimes related to the cooling system in these cars. Often it is the advance mechanism hanging up, or the advance spring(s) getting old and stiff if it has sat around, or just simple adjustment of the timing. Not advanced enough will cause overheating, while too much advance driving around will cause pinging.

Look for around 10 degrees advance at low idle, and it should go up another 10 or 15 degrees when you rev it with the timing light on it, depending on how high you rev it. This technique is for crude testing only.

[Tom Lange, MGT Repair]

I used to have a Mustang restoration shop, and every month or so we would get a frustrated customer insisting he or she needed a new radiator to cure a long-standing overheating problem. Nine times out of ten a new vacuum advance mechanism, properly adjusted, would completely cure the problem.

MOST overheating problems are indeed timing- and distributor-related, whether mis-set or just plain worn out. It does little good to set timing at idle, or guess when the car "feels" best - you need to start out with a properly-functioning distributor, use a timing light that displays total advance, and set the timing to 32-35 degrees of total advance at 3,200 rpm. A properly rebuilt and adjusted distributor (Distributor Dr. in Europe, Jeff Schlemmer at Advanced Distributors in the US) is the cheapest engine repair/tune-up you can get, and will promise accurate timing.

THEN, if the car overheats, you can figure out why, but most don't. There are only a few other cooling-related possibilities:
1) bad waterpump
2) clogged radiator
3) bad or no thermostat
4) engine with lots of rust and silt clogging the cooling passages
5) poor air flow to the radiator due to mis-adjusted grille slats
6) low or incorrect coolant

Tom Lange
MGT Repair

[SteveW]

Just out of interest, how good were these cars at keeping cool even when they were new, particularly in a hot climate?

Modern cars have replaced fans driven from a fan belt with electric fans that run at a high rate even when the engine is idling. A stationary car with no forced air flow through the radiator due to movement down the road and a fan turning only at idle speed does not make for efficient cooling. Modern aluminium (aluminum) core radiators are also better at heat transfer. All of that coupled with modern traffic congestion is probably not a good recipe for a cool running car.

Incidentally, I would add 'airlock in the pipes' to Tom's list

[Steve Simmons]

Copper is better at transferring heat than aluminum. The only advantage an aluminum radiator has, assuming equivalent core design, is weight. There are a lot of cheap, poorly designed radiator cores out there and they seem to be copper. So buying an aluminum one (assuming they are available for TC) is probably a good bet for getting a quality core. BUT, there are high end copper ones available also. You just have to make sure your radiator shop is ordering one of the good ones.

Electric fans do help in heavy traffic, but I just can't stand the sight or sound of them! If I ever feel the need to upgrade the fan, it would probably be with a flex fan or 6-blade MGB unit.

[stephen stierman]

These cars do not have pressurized cooling systems so often times on a hot day after a hot shut down, or idling in a hot garage, you will hear some coolant boiling. It may even put some out the overflow till the level in the radiator top tank is down below the point of overflow. The timing is set correctly on my car and given the right conditions, particularly with a freshly topped up radiator it will burp fluid on the floor. It does not boil when running down the road on a hot day and I suspect it has the radiator it left the works with.

[Steve Simmons]

Mine had its original radiator core and had no heating problems. I finally put in a new core when I rebuilt the engine because it failed a pressure test after boiling (tubes were super thin from age and corrosion) and several tubes had already been pinched off in a previous repair. Those original cores were really good. Even the best core available (and very expensive) did not cool any better than that 60-year-old one even with its reduced efficiency. I'm a firm believer that core design is everything. Flow rate, number of passes, overall time in the core, tube size, fin design / spacing, row spacing, tube pattern, etc.

[JeffMoore64]

So I'm confused as to what or why timing would have anything to do with the cooling system? I welcome an explanation on the subject.

Also, I don't have any temp gauges on the car, obviously the radiator should not go over 100 C unless the system is pressurised, which I don't think the TC is. If I measure the block temp with an infra red gauge, what would my expected ranges be?

Anyother way to make sure I don't over heat? Last thing I want to do is to crack the block or some how break something.

Thanks

Jeff

[Steve Simmons]

The timing has no direct effect on the cooling system, but incorrect timing can force the cooling system to work harder. I'm sure someone here can explain it better than I can but basically, the timing tells the engine when to ignite the fuel mix. If you ignite at the wrong time, you get less efficiency (energy lost to heat) and can trap hot gasses in the engine since the valves aren't opening at the right time to let them out. Retarded timing will greatly heat up the engine. As Tom notes, if your advance mechanism isn't working then that would be a huge problem. As RPMs rise, you need more advance. Without it, the timing will become retarded for the engine speed and heat will build.

The easiest method is to measure the top tank of the radiator. Or dunk a thermometer in the water through the radiator cap. To monitor on the road, you would install a motometer. Then once you're satisfied with running temps, remove it and put your original radiator cap back on.

[Julian Evers]

Following on from Tom's analysis, I strongly suggest that once everything he has listed is done the car is then taken to a rolling road and properly set up. You would be amazed at the effect that spot on timing and balanced carburettors with the correct needles has. More power, better heat dissipation and far smoother running engine across the complete (and beyond?) rev range. The needles quoted in the literature, ES for standard from memory, are a match for Pool petrol, a 75 octane horror available in the UK in the 1940's but long gone. Fuels have changed immeasurably since then and your XPAG is just a heat engine that happens to burn petrol and I bet that very, very few are in as built condition now anyway. Coincidentally I am off to an SU expert rolling road in 10 days time with my original distributor newly rebuilt by the Distributor Doctor. He was keen to know the exact state of tune of my engine and the fuel I put in it so that he could match the advance curve to it. He is hoping that it will beat the 87 bhp produced 4 years ago with a Mini-Cooper distributor. Watch this space.

Best regards

Julian