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MG MGA - Water temp reading high ?

Hi guys, well today's mystery for the A team is :

Took the A out for a run this afternoon, a ten minute run on country roads then onto the M27 but noticed temp gauge reading high, it seemed to go up fairly quickly, I was only out for 15 minutes.
Now I'll attach a couple of pics, but when I bought the car the guy had fitted a separate temp gauge because the original one combined with oil pressure was not working,

I did not have any steam coming out etc. And also when I removed the radiator cap there was not a lot of pressure like boiling water etc.
And the radiator did not seem exceptionally hot.

I have attached a picture of the old radiator cap fitted the the car, but I replaced it with the new one I had in my garage this new one is rated 10psi,
So I'm thinking firstly is the gauge correct, it's just a smiths one with C N H cold normal hot, or is it the thermostat not opening, or something more sinister,

What's the panels thoughts ?

Cheers Jack.


Jack New Forest

The pressure cap should be 7 psi - which replaces the 4 psi one originally fitted to 1500 cars. The cap should also be the long reach one that will compress when it is locked down - the short reach one will not compress and so water is not pressurised. Water temp should sit at the temp of your thermostat - mine is a 190F one.If you haven't changed yours since you bought the car or haven't a record of when it was last changed , it may be wise to open up the housing and put a new one in - although your photo shows it looking fairly fresh in that area.
On a long run on the motorway (1/2 hour)my temp gauge gradually creeps up to a little over 200F and the oil pressure drops as it thins out. Many owners on here have much lower operating temps (Steve and Dominic for example seem to get below 170F)
Cam Cunningham

I would first check the gauge by removing the bulb from the head and immersing it in boiling water. No need to remove the gauge from the dash.

Your cap pressure is a bit high - it should be 4 psi for a 1500 or 7 psi for a 1600. Shouldn't make too much difference but if you have an original radiator I would get the lower pressure cap.................Mike
m.j. moore

M.J.Moore: I tried that once, but my wife got really pissed when I drove the car into the kitchen to get close enough to the stove.
Still married, but just barely
Steve
S E Bryan

Jack

Cam and Mike have covered the obvious issues. certainly you should not be seeing those temps today (+4 to +7). I had mine out for a not too dissimilar run although I did not get on the motorway and the temp only went up at an expected rate and settled at 170 to 173. Even when I stopped back home the residual temp only went up to a tadge over 190.

Have you yet had a chance to flush out the system or have a look to see what sort of radiator core you have? Apart from the core tube and cooling fin design the whole core should be 2" thick if anything like the original spec. But I think that is probably for later, in the mean time you have something fundamentally wrong.

Steve
Steve Gyles

Yes Steve, something fundamental, I'll pop down to my local parts man, I think a new thermostat first, and when I put it in I'll flush the system and refill the coolant,
And fit a proper tad cap.

Cheers
Jack New Forest

Should read Rad. Cap.
Jack New Forest

Steve Bryan,

It's much safer to take the kitchen to the garage - more time to make a get away!....................Mike
m.j. moore

Did an 80 mile run last Saturday- Weather pretty cold temp steady on 170 all day even idling in traffic- rose to 190 when parked
Paul 1600Mk 2 Coupe
P D Camp

Lots of stuff in the archives on overheating. (Welcome to our world.) Volumes on the importance of getting air flow through the radiator and not around the radiator. You will find information on the felt strip, after-market fan shrouds, and of course the original core radiator.

There should be two 4" vent hoses running from the shelf in front of the radiator to the openings on either side of the radiator. One supplies fresh air to the SUs and the other to your heater via a third 4" hose. It did not appear to me that the hose running from the radiator shelf to the SU side is there. This will most likely not solve the entire problem but may help a little.

Good luck
Don Carlberg
Don Carlberg


Quote "I did not have any steam coming out etc. And also when I removed the radiator cap there was not a lot of pressure like boiling water etc.
And the radiator did not seem exceptionally hot."

Perhaps the level was too low and the coolant was simply not circulating

David
David Marklew

Ha ha - nice one Steve Bryan - I wish we had a kitchen big enough to fit the car in!!
Cam Cunningham

Don, (above) I'm interested in your comment re air ducts on both sides. I believe the ducts are important and most often overlooked.

On original cars delivered to Australia without a heater fitted, the duct opening (RHS) at the radiator bulkhead, had a fibre blanking piece to stop air-flow on that side. The effect would be to force air through the radiator as it was not needed for heating.
On Concours cars this fibre piece is often overlooked.

Barry.
Barry Gannon

Possibly your thermostat didn't open fully - wouldn't that explain radiator temperature not being particularly hot?
Gene Gillam

Ok guys I've taken onboard all the comments, so fitted a proper cap today, 4psl and took it for a run.
Interesting, temp gauge gradually rose to H after about 15min.
When I stopped and just let the engine idle, the temp dropped to N
When I got home I checked the coolant level I was able to Top it up with just over a pint.

Silly me I should have checked the coolant before I took it out, to prove a point.
Anyway coolant topped up and I'll give it another go on Monday, I'm away for the weekend tomorrow back Sunday.
If no change Monday, then I'll check the thermostat, and also take onboard the comments about the 4" hose I only took it off while I source a new one, old one is torn.
I did not think it would make any difference but I get your point about air bypassing and not getting to rad.

Cheers Jack.
Jack New Forest

Just another possibility Jack if it is OK at idle but not running - is the water pump actually pumpin? I had one on my MGB that seemed OK but after overheating a couple of times on short runs - I took it off and found that the impeller had come off the shaft so was not spinning and pushing the water round
Cam Cunningham

Jack

Unlike your MGB the MGA is a total loss water expansion system unless the previous owner has fitted an overflow catchment system - either pressurised like the B or vented. Therefore you will always have a bit of loss on your first run after a refill, then it should remain constant.

Steve
Steve Gyles

Hi guys, thanks for all the comments, I've fitted the correct Rad cap 4psi,
I now have a new thermostat to fit, and some new coolant, so next job I'm doing is to take out the radiator, as this car is new to me I don't know how old the rad is, so I'm going to take it out and give it a good clean and flush out, then refit and refill with new coolant and new thermostat, at least I know I've covered that and I know it's all ok. If I still have high temp then I'll look at the gauge.

Any suggestions on what to use to clean out the rad ?

Cheers Jack.
Jack New Forest

Well still on the trail of High temp problem, before I remove the rad to flush out, I'm trying with a new Thermosat,
I had a devil of a job getting the old cover off, this car was supposedly restored, but looking at this thermostat and gasket it's been there since the year dot, so let's hope this solves the problem.

Well you did warn me owning an MGA was lots of fun and lots of heartache bring on the fun !

Cheers Jack.


Jack New Forest

"Well you did warn me owning an MGA was lots of fun and lots of heartache bring on the fun !"

Now you tell me!! :-) I just acquired my '62 MGA Mk II from the original purchaser last week. Here's a pic of the engine compartment showing the 4" duct to the heater box (I know, it should be unobtrusive black paper but I didn't install it). There is a short duct on the carb side the ends just aft of the radiator shroud. I've done runs of 70+ miles in 75 degree F at 60 mph and the coolant temperature
stays right at 185F.

My '72 B with an electric temperature gauge was indicating quite high. I suspected that it was either the gauge or the electric sending unit. I used an infra red thermometer (wife bought it - probably at Harbor Freight) to confirm that the actual temperature of the head and the top of the radiator were what they should be.

Jud


J. K. Chapin

Thanks for the info Jud.
Jack New Forest

Barry, my California MGA 1600 came without a heater and had that blanking plate installed. I had to remove it when I installed a heater in the car.
Don Carlberg

Well boys that done the trick, new gauge fitted, took the girl for a spin, plenty of revs got the temp up and reading between 165 175, 160 on idle, problem sorted, I hope.

Cheers and thanks for your help.

Jack.
Jack New Forest

Cool runner now. Join the clan. You are now an authority after all your investigations.

Steve
Steve Gyles

... what you need now is a good Bank Holiday Traffic Jam!
But doubt if you will find one tomorrow - the weather forecast isn't that tempting.
Graeme Williams

This thread was discussed between 08/03/2016 and 27/03/2016

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