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MG MGB Technical - overheating B roadster

Hi all
I know that a lot has been written about this in the past but I need to ask anyway.
Just finished restoration of 1970 B roadster - reconditioned engine, new parts as follows (all from MGOC): radiator, distributor, coil, alternator, carbs, oil cooler, heater matrix, water pump, combined oil pressure and water temp guage. Essentially everything was replaced. Car has been tuned by local mg specialist- mixture, timing etc. I have been running it in - 450 miles so far, nearly all on m/way not going above 3-3500rpm. Runs well and smoothly, oil pressure 60 on idle, 50-60 on run and not using any oil, idles well, accelerates smoothly.
Now to the problem. Overheating. On the run temp guage will range between just above N to halfway to H if I'm going up a gradient. I've been careful not to labour the engine on these runs. I am using Four Life radiator fluid (from MGOC). No leaks either.
When going through town temp guage creeps up into hot band so I have turned on heater which lowers temp a bit. Checked thermostat and it opens and closes ok. I used the 3 bladed fan (fitted the correct way round).
I am stumped as to the overheating. I expected it to run a bit hotter sometimes because they do. Could this be because new engine needs to be run in. If so when should I expect the temp to behave sensibly? Should I install the Kenlowe electric fan now or should I wait till I've got a few thousand miles on the clock and the engine is run in a bit more and do it then if it still runs hotter than I think it should?
Thanks in advance
Derek
D W Adnitt

Derek
I have also just got mine back on the road (a 1980 GT) and have been seeing high temps.
First of all, the engine will still be tight, and you don't say what spec your engine is, but I assume normal, or is it tuned.
Secondly, the weather is hot at the minute! The cars weren't designed for such high temps. I remember my 1965 roadster in South Africa used to run a little hotter than I liked on the metal fan.
On my current project, I installed a Pacet electric fan tight against the radiator on the engine side to suck air through. My rad already has a sensor switch so it was an easy upgrade. I may still fit a manual override switch as it does not seem to kick in early enough.
Prior to taking mine off the road in Winter, it was running similar temps on the gauge so I'm not too worried.
If your car is a daily use, then go for the Kenlowe now. If not, and originality is important, leave it alone but check that you are still spot on on the carb and timing set up. As the engine beds, these will need attention. Make sure it is not too retarded as this will cause overheating, too. So long as the temp drops when moving, expect a certain tendency to run hotter when stationary and idling.
Also on your running in avoid motorways and constant revs. Try using the gearbox as much as possible to vary the revs.
Apologies for the waffle, but I hope it gives you some comfort. I am sure others will have more to say.
Martin

'lo

When my engine was new I ran it in in the middle of summer with no overheating problems. Only serious difference to my setup was the 7-bladed plastic fan. Idling in town it would actually start to cool down.

How much ignition advance are you running? I use loads and it makes for a happy engine. When I mistakenly fitted an A-series disi it all overheated very quickly...

hth,
--
Olly
Oliver Stephenson

Thanks for that Martin,
Yes it is standard engine in standard tune. It isn't my daily driver yet but I'd like it to be but I'll think I'll wait till it's bedded in a bit more.
good point about the m/way driving so back to the A roads in the early morning (only time they are anywhere near clear here in the S East. What do you think about fitting a 5/7 bladed fan?
Derek
D W Adnitt

Hi all.

My 1980 BGT ran very hot when I bought it.

The biggest improvement that I obtained for this condition was when I moved the front number plate up to the front of the (rubber) bumper, which allowed a much better airflow through the under-bumper orifices.

I also removed the rubber seal from the engine compartment edge.

My electric fan rarely cuts in these days.

HTH... Don
Don

I bet it's the new radiator. See the current thread on "BEST rad". I'm afraid to say that new radiators are generally not as efficient as they should be. They certainly don't hold a candle to the original. I chucked out a leaking original for a new one - what a mistake to make. Should have had the old one recored. The new one can only just cope with summer (electric fan on constantly in traffic, and only just holding it's own at 40 mph), whereas the old one had loads of spare capacity. And the new one now leaks at the top hose elbow where the soldered joint is.

Mike
Mike Howlett

Mike - All is not lost, although it is too bad you discarded the original radiator, the replacement unit can be recored with the Modine cores. This was done with a replacement radiator in my daughter's MGBGT and it works fine. You can get that top elbow fixed at the same time.

It always leaves me wondering when someone says that their car is overheating when the gauge is reading between the N and H. By definition, an engine is not overheating as long as it is not boiling (steam coming out from under the bonnet) or the engine is not starting to miss while the car is moving. We just got back from a weekend event in Eastern Washington State, where the temperature was 95+ degrees F (I'll let you do the math to degrees C)and we were driving over a 4000+ ft pass in our TD. The temperature gauge went right up to 100 degrees C before we were half way up the pass, but the car never missed a beat. As soon as we crested the top of the pass it dropped back down to it's normal 85 - 90 degrees C (it has an 85 degree C thermostat in it). Our MGB is taken on trips to California, where summer time temperatures get into 3 digits F quite regularly. The MGB takes all of this in stride, running at 190 degrees F normally and going up as high as 212 degrees when climing hard grades. I sometimes think that we worry too much about what the gauge is reading (have you checked the calibration of the gauge to see what the actual temperature is at N, half way between N and H, and H)? The gauge could be exaggerating the temp (kind of like a present day administration did with the threat of nucs in Iraq). I don't start getting concerned about temperature untill the temp portion of the dual water temp/oil pressure gauge in our TD and 66 MGB starts to read into the PSI scale. To paraphrase Neil Cairns' comment about oil pressure, I wonder what we would worry about if we just had an idiot light that comes on microseconds before the radiator cap erupts through the bonnet.

Having said this, Derek, I don't know what the radiators from the MGOC are like, but all the other after market radiators I have seen or heard about are junk and if you are really having a problem, I would seriously recommend having that radiator recored with a Modine type L 4 row core (see thread on "BEST rad" as Mike suggested for details on the Modine Company) before going to the electric fan. The fan just treats the symptoms rather than curing the problem. Also, once you get above 20 MPH, there is more air being forced through the radiator than the fan can pull through. You might also make sure that all air gaps around the radiator and the diaphragm are closed off so that all the air is forced through the radiator.
Good luck - Dave
David DuBois

Hi Dave
Thanks for your comments. I take the point about not the overheating if temp is between N and H - I think I was more worried about damaging the new engine by letting it run right up to H.

Mike
I read the comments on BEST radiator, sounds like the rad I got from the club might not be up to scratch, no probelms fitting it though, and having just forked out for it I'll have to stick with it!

I had no problems with my previous 69 B although that did still have an original radiator fitted......

Derek
D W Adnitt

Dave, your comments are well worth the reading. You are quite right that having a gauge is a mixed blessing. I don't have an engine fan any more and tend to switch on the electric fan when the gauge reads 200 degrees F. But, as you say, it ain't going to boil for another 30 degrees or so. However, it does start to idle very poorly. I really must get around to sealing off the front of the rad from the engine - big gaps there.

Derek, one thing the MGOC are very good at is giving refunds. If you aren't happy with your rad, I'll bet they would refund you.

Mike
Mike Howlett

First, see if you really have a problem by testing the guage - take the sender out and place in a pan of boiling water without touching sides or bottom.

That will give you the 100 C (or 212 F) point on the guage.

It is OK to run the engine up to this point as long as the system is under pressure.

New engines will run a bit hotter until they bed in fully - anything up to 5,000 miles but normally around 1000.

Please double check the ignition timing and retard it slightly to be on the safe side - I have seen the disasterous result of running a new engine with too much advance - a "U" shaped number 4 conrod!
Chris Betson

Hi All
I have owned my rubber bumper B for a good number of years now, and it has tended to run much hotter since it was converted to unleaded this has become even more noticable since the low sulphur unleaded appeared. The car is by no means overheating but the electric fan does tend to cut in more often in heavy traffic on hot days [I have a small red diode that tells me when the fan is running]
Quite a common cause of an engine running too hot is retarded timing so it is worth checking the timing occasionally even with electronic ignition and set the timing to suit the fuel rather than some figure out a manual that was designed for the fuels available when our cars were made
Ron
R. Algie

Mine is a standard 73 and last weekend on the Cheshire Run in the low 30s C it was running slightly warmer than normal but nowhere near as high as you describe. Bowling along it was on N instead of an N's width below, in traffic it was maybe an N's width above. Only when switched off at the end did the needle rise into the H band, which is the hottest I have ever seen it. And all this was with a 13"x7" rally plaque right in front of the grill. What I'm saying is that I think there *is* something wrong, it is not just the weather.
Paul Hunt

Regarding gauge readings check the archives for previous posts on gauge calibration. Also check the excelleant "Electrical Help" link on this forum. Under instruments it has ohm/temperature values for the temperature sending unit.
Andrew Blackley

You might want to check your distributor, make sure it's the proper one for your car, and if rebuilt that it was done with the correct parts. The number stamped into the cam that controls the max advance is most important.

http://www.teglerizer.com/mgstuff/advance_curves.htm has got the information you'll need. For example, if you've got a different max advance cam that was original for your engine, you need to use a different static advance setting. http://www.telusplanet.net/%7Echichm/tech/lucastuning.pdf has a picture and a description of why.

I've got a 70 with a freshly rebuilt engine and it runs around N, creeping only a little above N on hard (80mph+) runs on hot (30C) days. I use the "hot" thermostat in my car even in the summer. Of course the temperature goes a lot higher if I stop the engine after a hard run.

I discovered the hard way that low cost rebuilt distributors can come with the wrong cam :(.
Mike Polan

Duh, a I forgot to mention - when I was running the distributor with the wrong cam, I would run half way between N and H even in cooler weather on the highway - probably because the time was too advanced. The fix was simple - I used my old cam in the rebuilt distributor and now the temp is perfect.
Mike Polan

This thread was discussed between 15/07/2003 and 18/07/2003

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