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MG Midget and Sprite Technical - Any ideas? (coolant issue)

Just wondered what you guys thought as I'm scratching my head a bit...

Had a great 1 hour plus blat over the moor last Friday, and literally about 500 yrds from the house as I was turning into my road, I got a massive plume of white steam shooting out from under the bonnet, and it seemed from under the dash too. It stank of hot coolant, so I immediately shut the engine off. I noticed that the temp guage had gone to 90/95 and the kenlowe hadn't cut in (had been fine during the drive), which I guess is because the pick up is from the water in the top hose, so no water = no way to measure temp?

When things had cooled down a bit, I released pressure and removed the rad filler cap, but while the level had dropped, it only took about 400ml to fill back to correct level.

Drove it home, put it away, and didn't think too much more about it until I dropped by the garage this morning and had the mechanic look at it. He couldn't find any obvious issue, and assured me the head gasket was fine. He did say that the flow of coolant between the rad and the expansion bottle may be the issue, but would require longer to properly diagnose.

I drove it for a good hour, quite hard at times, after leaving the garage, and no problems or temp' spikes. Kenlowe working OK. Though when I went to pop her away for the night, I noticed a patch of coolant on the drive under the rad area.

Any ideas?

M Weller

Lots. After inheriting mine after a long stand in storage and having all sorts of cooling issues I eventually took the cooling and heating systems apart and back flushed everything a lot twice over two weekends. (Nigel moaned at me till I did it). The muck that came out of the expansion tank, engine jacket and radiators (heater as well) was amazing. In fact I always wonder just how much coolant was actually in there. I am sure some of this muck was floating around and causing allsorts of fluctuations. Had 3 years of cool engine since. In fact I have a high temp thermostat in a 1500! helps me keep warm tootsies in the winter.

Suggest you check how much coolant is in it and if not much give it the flush out till you get the correct amount to go in. If you do flush remember to put the anti corrosion coolant in after. Helps keep the crud at bay.
Dave Squire

Is it 1500 or 1275?

Dave is certainly right about crud. All this came out of this one small hose. It was completely blocked. (although it didn't cause any specific problem to me as it was mid-restoration and I hadn't ever had the car running)

Malcolm Le Chevalier

Dave, thanks for those thoughts. I've only had the car a month or so, and the PO hadn't used the car much during the preceding 12 months, so I guess a full coolant strip and flush wouldn't go amiss.
M Weller

Sorry Malcolm missed your post there, it's s 1275. Which hose are you referring to above ?
M Weller

See the attached picture. It was one of the hoses to the heater if I remember.
Malcolm Le Chevalier

That hose looks like one I sorted but mine was all wet rust. The expansion tank and radiators were each half full (literally) of a sort of clay gunk. A lot of floating rust in the jacket. Needed to poke the drain hole continuously to get fluid flow.
Interestingly I put all the original hoses that I could back and they are still in good condition 4 years later. The odd new rubber hoses are fraying at the ends.
Dave Squire

M Weller,
if you email me I'll send you my easy but thorough method(s) that I "moaned*" Dave and others into trying/doing.

my first and last name at bt internet dot com (no spaces or capitals

* moaned? me? really??!?, narh.
Nigel Atkins

I had a similar thing happen to me recently in France on a very hot day. It turned out that there had been a bad connection in the Kenlowe circuit and it hadn't cut in. I reset the adjuster a bit lower and all was fine until I got back to the UK and investigated.
As the pressure built up, the rad cap didn't blow off, but the coolant managed to force it's way out through the bearing of the not very old water pump. With the fan set lower, it was OK, but when set to its normal cut in setting, the problem happened again even though the fan was now OK.

A new water pump cured it, which raises the question of the quality of replacement parts again. I'm now on my third pump in 19,000 miles.

When I rebuilt my engine, I removed the then 40 year old iron pump as a precaution, even though it was working OK.
The aluminium replacement lasted about 8,000 miles before it became very noisy, then the last one started to fail in France.
Bernie Higginson

Bernie - where do you have the Kenlowe fan setting now? Mine doesn't seem to have a marker from which to align the indexed dial. It's mounted above the o/s/f arch, and standing by the o/s/f wing looking down on the dial, the 'N' setting is effectively 'against' the wing with the H & C settings pointing to the front/back of the car. So, I guess I currently have a neutral / normal setting.
M Weller

check the connections are all clean, secure and protected, on my midget I had a modern spade connector loose that stopped my fan cutting in, it looked fine but wasn't.

Also check the wiring, on a Rover P6 I had with a Kenlowe fan the previous owner had wired it in on the same fuse as the added-in electric fuel pump so when the fuse blew it stopped the car.

You want to set the dial so that the fan cuts in and out after the water thermostat is open. You should be able to see when the water stat opens by watching the temp gauge when the engine is first warmed up as there will be a sudden (slight) drop on the needle after the steady rise.

Nigel Atkins

Park the car outside your garage and get an assistant to video the engine bay while you gently warm up the engine with the bonnet open. Once the engine is warm hold the revs on about 3500 and wait to see what happens. If nothing happens and the fan comes on,disconnect the fan and try again. Keep an eye on the temp gauge at all times.
Daniel Stapleton

Hi lads, Nigel you are correct, the fan is best wired seperately, a big fan can draw as much as the headlights, say 120 watts.
I found this pic of the recommended fitting of the Davies Craig/Kenlowe capillary tube, personally I don't like this as I have had it fail on one of my cars with an almost catastophic loss of coolant. However with careful fitment and the use of silicon gasket sealant, it should be fine.

R W Bowers

What are the advantages to fitting it here as opposed to the thermostat end?
M Weller

there's sometimes debate about fitting the probe in the bottom hose, though I can't recall this being suggested on a Spridget and I don't know how convenient this would be for installation and if you need to get at it later ([dangerously] presuming you have a vertical flow rad based on the other thread).

As the fan has a variable stat control I'd have thought its location as far as controlling the temperature the fan kicks in and out doesn't matter as you adjust its setting accordingly.
Nigel Atkins

I think there was some discussion recently on the MGA BBS about the fan stat, and it was suggested that the bottom hose was better.
Dave O'Neill 2

The argument I know about where to place it says to put it in the outflow from the radiator as that indicates the water is coming out too hot and so needs the fan running to cool the coolant. Having it in the inflow may turn on the the fan when not required as the coolant is going in hot but may be coming out of the radiator at an acceptable temperature.
David Billington

How do you get the capulariary tube / wire out of the hose/radiator.... it seems to me its exit point would be a prime location for coolent leakage loss

i can certianly see the reason for putting the senor on the exit flow as thats the cooled water over theheated intake of the coolent... id never considard that before

plus if your fluid did run low from a leak what fluid is left will all ways be cooled where as if the sensor is on the other end... the senor maybe dry and not detect a high temp taking place

great point

i guess you could make a sleve with a sensor hole to fit into the lower hose...maybe modify an old black KAT engine heater would be the easist ...

Prop and the Blackhole Midget

I seem to recall reading somewhere in Kenlowe's bumpf That they recommend the variable temperature control knob is not set at too low a setting otherwise the fan will run more or less continuously, therefore shortening it's working life (with possible warranty issues?)

This thread was discussed between 28/09/2016 and 01/10/2016

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