The black art of cooling grey motors

[ardiesse]

There are some Holdens which just never overheat.  My father's FJ was one of those.  It would have been 1964 (I was too young to remember) we were driving from Perth to Armidale.  My great-aunt was with us, and when she drove, she drove at 80.  Miles.  In the stinking summer heat.  The you-beaut Toyo tyres Dad bought were turning squishy and losing their treads.  Inside the car, we were expiring from the heat.  But the FJ never complained.  Never lost its cool.

There are some Holdens which are chronic overheaters.  My FC is one of those.  When I was restoring it, I knocked the welch plugs out and Gerni'd all the scale and mud out of the water jackets.  I cleaned and reverse-flushed the radiator, and thought I'd be ok.  Around town, it usually was.  Long trips were a different matter.  I overheated twice on the way to the 2012 Nats, at Broken Hill and Ceduna.  Even going to Tassie in 2014, I lost about a litre of water between Sydney and Melbourne, and also on the return trip.  Repeat in 2016.  I lost most of my coolant trying to keep up with Mick Koetsier between Brisbane and Toowoomba.  The final straw was driving out to Penrith in November for the Christmas party, thinking, "hmm, smells of coolant" and having the temperature light come on right at a servo at Emu Plains to find I'd lost maybe two litres of water.

The symptoms were:

Cooling system pressurises, even on a short trip.  Even though the radiator doesn't feel all that hot to hand.

The coolant foams, even on a short trip.  One exception though: climbing Mt Roland in Tassie one morning when it would have been about zero degrees.  I undid the radiator cap after stopping.  No foam, no pressure.

On longer drives, the cooling system loses coolant.  Which then covers everything in the engine bay.  At the end of a long drive, I'd usually leave a small puddle of coolant on the road where I stopped.

It's beginning to sound like localised hot-spots in the engine, somewhere.

The preventative measures I took were:

Remove the thermostat.  Shit yeah.  At the end of a 40-degree day in Ceduna with an overheating car, why not?

Give the radiator a good clean-out with oxalic acid, followed by a reverse-flush.  Give the engine a good oxalic acid clean-out while I'm at it.

Pull the motor out, strip it down, get the block decked and the head machined to eliminate the possibility of a leaking head gasket . . . this turned into a rings-and-bearings job and a spun rear main oil seal fiasco.

Test the pH of my radiator water afterwards and confirm that it's pH 7, so no leakage of combustion gases into the cooling system at all.

Replace the aftermarket water pump with a good original one.  No change in temperature.

Try a different radiator.  No change in temperature.

Bugger it.  I'd just finished watching the Triumph Stag episode of "For the Love of Cars" where the garage used IR imaging cameras and temperature probes to determine the behaviour of the Stag's dodgy cooling system, and thought, "if the Poms can do that with a Stag, I can do the same with a Holden."  I "borrowed" a four-channel digital thermometer from work and bought a couple of stainless-sheathed industrial thermocouples and the right adaptors to suit 1/2" BSP.  I put the industrial thermocouples in the cylinder head at the threaded holes (it's an EJ motor), taped a third thermocouple to the radiator top tank, and a fourth to the radiator bottom tank.

And this is what I found -

This was a cold day in July, about 17 degrees, after climbing Mona Vale Rd to St Ives.  No thermostat in cooling system.

Top tank: 57 (i.e. ambient + 40)
Bottom Tank: 52 (i.e. ambient + 35)
Rear cyl head: 78 (i.e. ambient + 60)
Front cyl head: 78 (i.e. ambient + 60)

It looks like the radiator's doing its job, but something's seriously wrong with coolant flow inside the engine.

I figure that there's a hydraulic short-circuit inside the motor: the two holes in the block and head in front of number 1 cylinder.  The water pump is pumping coolant into the block, but most of it is going straight up in front of number 1 cylinder, into the head, out the thermostat housing and into the radiator.  The rest of the engine is being starved of coolant, leading to localised boiling, coolant loss, foaming, pressurisation at low temperatures, and if not stopped, a cracked head.



I don't want to push my luck with Photobucket too much now that I've linked an image, so I'll hit "post".

Rob

[Errol62]

Fascinating reading. Can't wait till you get to the chapter where you pressurise the cooling system with liquid nitrogen.


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[ardiesse]

Errol,

The liquid nitrogen is used to cool resistive loads when doing noise parameter measurements on low-noise amplifiers.
Wait a minute.  That's what I get paid to do.

Did I ever mention that the old-timers at work used to remove their own warts with a cotton-wool bud dipped in liquid nitrogen?  More convenient and much cheaper than getting it done by a GP . . .

Rob

[ardiesse]

So my FC's motor is suffering from poor coolant circulation right where all the heat is being generated.  It would be good to confirm the previous temperature measurements on another motor, and fortunately I have one to hand: a "parts-bin" 3-3/16" bore FB motor which I run on a stand.

Same July day.  17 degrees.  No thermostat.  Running at idle puts the most stress on the cooling system.

Top Tank: 56 (i.e. ambient + 40)
Bottom Tank: 50 (i.e. ambient + 35)
Rear cyl head: 66 (i.e. ambient + 50)
Front cyl head: 67 (i.e. ambient + 50)

By and large the measurements are confirmed.  The radiator temperatures are the same as before.  Coolant temperature is higher inside the engine than at the radiator.  Although the temperature rise is ten degrees less in this motor.  Makes me think that for reasons unknown, EJ motors are more prone to overheating than earlier grey motors.  Which may be why this item appeared . . .

GMH Service Note AN 1627

In 1963(?), GMH released a revised head gasket, part number 7424869.  The fitting instructions read:

"Fitting this gasket results in an increased flow of cooler water to the rear cylinders and valve seats, and is designed for use on vehicles operated at prolonged high speed or under conditions where severe operating temperatures are experienced.
1. Remove cylinder head and thoroughly clean all carbon from around cylinder head and block.
2. Rework existing rear water jacket holes in cylinder head and cylinder block to dimensions shown in Figs. 1 and 2. (Hole on LHS to 5/8", hole on RHS to 7/16")
3. Remove all burrs from around the the holes, then flush out filings from the head and block.
4. When fitting the cylinder head gasket it is important to ensure that the gasket is correctly located, so that the revised holes in the rear of the cylinder block coincide with the holes in the rear of the gasket."

"NOTE: A number of cooling holes in the cylinder head and block are blanked off by the new gasket; this is normal and is designed to direct a greater flow of cooler water to the rear of the engine."



I managed to score one of these head gaskets from Stan Bennett at a swap meet a couple of years back.  Twelve holes in total are blanked off in this gasket: two in front of number 1 cylinder, three on the left side under the inlet ports, both holes beside number 1 combustion chamber, and the front holes beside combustion chambers 2 to 6.

I figured I could try to "fake" a revised head gasket by cutting blanks out of Teflon sheet and putting them in the holes to be blanked off.

Bear with me a bit.  I've got some photos, but they're on my camera, and I don't have it with me at the moment.

Rob

[ardiesse]

Now I got to work with the Teflon sheet, cut out the blanks, pulled the head off the "test" motor, and fitted the blanks in place.  I drilled the small hole behind number 6 out to 7/16", but because I didn't have a 5/8" drill, left the other at its original size.

This is what it looked like before I put the cylinder head back on.



The head gasket to the side of the motor is the modified version, 7424869, showing the holes which are blanked off.

Bolted the head back on, and . . .

Winter day.  17 degrees.  No thermostat.

Top Tank: 55 (i.e. ambient + 40)
Bottom Tank: 50 (i.e. ambient + 35)
Rear cyl head: 56 (i.e. ambient + 40)
Front cyl head: 57 (i.e. ambient + 40)

The GMH engineers knew their craft.  The temperature distribution inside the motor is significantly improved, and peak coolant temperatures have been lowered ten degrees.

Here's the "test" motor on its stand, with thermocouples inserted into all its orifices:



I think I know what I have to do now to my FC's motor, but it's going to be an engine-out job.  Again.  Because there won't be enough space to get a drill down behind number 6 cylinder.

Rob

[Errol62]

Brilliant. In the mines they would put liquid nitrogen in the 180 and 240 tonne dump trucks tyres to reduce temperatures and increase life.


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[hsv-001]

Rob , could you give me a short explanation of why oxalic acid to clean engine block . Years ago I would use it to clean leather when building stock saddles . I know it is commonly used to clean timbers before staining or varnishing . I just thought it might be too mild to do too much , but maybe that is the point . Cheers Haydn

[hsv-001]

Sorry posted before I was thinking . 1989 was travelling from Brisbane to Thargomindah . The motor I had was only in place for about a week and I had been told it was originally built for a speed car . I had to give the original triples back to the guy but I could not get it to run well with the existing cam. Anyway long story short ,about 7 hours of average speeds 80 to 100mph smelt water boiling so I stoped at the upcoming small town for coffee and some water . I drove that same motor for years at 60mph and never had a problem after that , so I guess the water [coolant ] can flow too short and too fast and I believe that the original splash guards can make a huge difference .Haydn

[ardiesse]

Haydn,

Oxalic acid is often used as a bleaching agent, for example, I bought mine as Diggers "Rust and Stain Cleaner."  Chemically, it's a weak acid, but it forms a complex with the Fe(III) ion.  In English, that means it dissolves rust, but only reacts slowly with metallic iron.

And a warning.  Oxalic acid is poisonous.  It's the active ingredient in rhubarb leaves, which is why you don't eat them.  And oxalates, the compounds, are nasty too.

That said, I've found that oxalic acid is fantastic for getting the rust off tools.  A day or so in a concentrated solution works wonders.  And it also works really well for removing rust sediment from inside radiators and cooling systems.  On rust scale, oxalic acid works much more slowly.  It seems to loosen scale, rather than actually dissolving it outright.

Rob

[ardiesse]

Deep breath.  After my local Repco took two weeks to acquire a grey motor head gasket (you just don't want to know . . .), I pulled the motor out of the FC on the weekend before Christmas.  It's much easier to do a job like this one when the motor and gearbox are in a stand.

Step 1 was easy.  No it wasn't.  The newer style of head gasket glues the head effectively to the block.  My usual trick of socket-extension-in-inlet-port-and-lift didn't budge the head.  Neither did cranking the motor over.  With hindsight I should have loosened all the head bolts off a couple of turns and started the motor.  Instead, I dodgied up a cylinder head jack.  It's a piece of steel which sits on two head bolts, and has holes to engage two bolts where the rocker pedestal goes.

Here it is:



Step 2: Taking a drill to my motor was a stressful business though.  The drill tended to catch at the end, so I finished the holes with a round file.  Then there was

Step 3.  At first I used a magnet-on-a-stick, but I drew up scale, mud and swarf in equal proportions.  So I Gerni'd the water jackets until no more mud or scale came out the drain-plug hole.  The cylinder head was easier to clean out.  Which left the radiator.  I filled it with oxalic acid solution, laid it flat on the BBQ, and brought it up to a gentle boil.  Poured the now murky oxalic acid out, and did a reverse-flush with a garden hose and an air gun, until the water came out clear.  I had to fish a fair bit of scale out of the top tank with the magnet-on-a-stick, and kept flushing and removing scale until no more scale came out.

Step 4 meant cutting the blanks out of Teflon sheet until they were just the right size to go in the holes in the head gasket.  The Teflon blanks are bigger than the water jacket holes, so they'll stay sandwiched between block and head.  And yes, the Teflon sheet is thinner than a head gasket.

Step 4a: Repaint sump where four years of coolant dribbling out the overflow stripped the paint off.

The only other, minor fix was to replace my rocker gear with another, nearly new set, so that number 1 rocker, valve and pushrod are lubricated properly.

Boxing Day.  J-series engine in test stand, after cooling system fix.  No thermostat. 23 degrees ambient.

Top Tank: 63 (i.e. ambient + 40)
Bottom Tank: 64 (i.e. ambient + 40)
Rear cyl head: 67 (i.e. ambient + 45)
Front cyl head: 69 (i.e. ambient + 45)

This is very encouraging.  With the motor back in the car after Christmas, on a stinking-hot day (29/12) I took off up the M1, and tried keeping up with the trucks from the Hawkesbury River bridge uphill to the Mt White exit.  At Mt White, maybe 35 degrees, still no thermostat, tap water only -

Top Tank: 85 (i.e. ambient + 50)
Bottom Tank: 80 (i.e. ambient + 45)
Rear cyl head: 88 (i.e. ambient + 55)
Front cyl head: 90 (i.e. ambient + 55)

Call me foolish, but I took the radiator cap off.  Just the slightest "fshh" when I got to the first stop, and that was all.  When I got back home, say 30 degrees ambient,

Top Tank: 75 (i.e. ambient + 45)
Bottom Tank: 69 (i.e. ambient + 40)
Rear cyl head: 83 (i.e. ambient + 55)
Front cyl head: 84 (i.e. ambient + 55)

No coolant loss, even though the radiator was 1/2" below full.  Compared with last July, the cooling system fix means that the coolant temperature inside the engine is only say five degrees hotter; and the ambient temperature was nearly fifteen degrees higher.

Next step is to put the thermostat back in, and if things are satisfactory, drain and refill the cooling system with coolant.  And just to be on the safe side, I should go find a radiator place which is prepared to take the tanks off and clean the core out.

Postscript: the FC's previous owner finally admitted to me that if he drove it at more than 40 mph on long trips, it'd overheat.

Rob

[mcl1959]

This is a very informative post Rob, and I am thoroughly enjoying it. I too have had one of those motors that just Continuously overheats on long trips.
I think the fix is excellent and could be very useful.
Do you have a theory why some motors run hot and others not?

Plenty of engines give the impression they are running hot when the temp light flicks on, but the radiator is not boiling. This is usually caused by having the wrong temp sender in the engine.

Also rebored motors usually run hotter than unbored ones due to reduced wall thickness around cylinders

Ken

[Errol62]

Great stuff Rob. As Ken says my 192 always ran hot at speed despite a three core HR radiator. Replaced with a standard bore 202 and the smiths temp gauge in the head sat rock solid on 82C. 82C thermostat fitted.


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[ardiesse]

Ken,

As to why some motors overheat and some don't, I'm still in the dark.  My FC's J-series motor is the only stubborn example I've found, as against two earlies and three B-series motors that run quite cool, although my 48 needs to be driven with one eye on the temperature gauge on a 38+ degree day.  I wonder . . . did GM increase the wall thickness of the block and head castings when the EJ came out?  Something inside the block is impeding water flow to the back of the motor, and so it finds the easy way, which is the short path in front of number 1 cylinder.  Was the release of head gasket 7424869 just before (or even after) the end of grey motor production a tacit admission by GM that some design change for the J motors had bad consequences for cooling?  But then I remember the stories friends told me about going on family holidays in Hydramatic station wagons . . . The last thing a Holden cooling system needs is the extra heat load of an automatic transmission oil cooler.

And I will (respectfully) disagree with you on the rebored motor running hotter theory:

1: My "test" 3-3/16 bore motor ran cooler in its "natural" state than my FC's 3-1/8 bore motor.  With the cylinder heads off both, I noticed that the 3-3/16 bore motor was easier to turn over by hand, and so I'm not surprised that it runs a bit cooler.
2: Thermodynamic considerations.  The fuel's calorific content can only emerge in three places - at the crankshaft hub as useful work, out the exhaust as heat, and out of the cooling system as heat (neglecting  direct thermal transfer from motor to surroundings).  The only way that thicker cylinder walls could impede heat transfer is if they had quite significant thermal resistance, which would imply high temperature gradients in the cast iron.

One of the guys in the 48&FJ club put a reconditioned motor in his 50-series ute about ten years back.  And the reco motor was a chronic overheater.  He reverse-flushed the cooling system, replaced the thermostat, checked the calibration of his temperature gauge, re-cored the radiator, checked the motor for leaking valves, compression-tested it.  On a summer's day, it would boil over.  Like clockwork.  In desperation he pulled the water pump out and checked the clearance between the impeller and the pump body.  He ran out of feeler gauges at 70 thou, and they were still a loose fit.  He replaced the water pump with one of correct clearances, and all his overheating troubles vanished.

He's still annoyed that it took him nearly ten years to work out what was wrong.

Errol: My experience of red motors is that they only overheat for good reason, either component failure, or that the radiator's completely blocked with rust scale.  Mind you, I'm suspicious of the pressed-sheet-metal impellers on red/blue/black water pumps these days.

Rob

[mcl1959]

Good point Rob, I guess your title of "black art" is quite apt.

I've never had success with rebored motors cooling wise and all my original motors have been fantastic.
I'll have to come up with another theory.

Ken

[Harv]

G'day Rob,

Very cool post  . I appreciate the science being put into understanding how the grey is working.

Oxalic acid is funky stuff. I used some many years ago to remove heavy watermarks from a rosewood coffee table. Wonder I didn't poison myself.

If I read the post right, the standard 2017 aftermarket head gaskets for grey motors are of the early type (too many holes), but can be converted to super-dooper late EJ ones (better coolant flow) by using the Teflon plugs, and some careful cylinder head drilling? Methinks there may be a market for those Teflon plugs  . I'm thinking this might be just the trick for my meth monster project.

One of the common lumpy humpy tricks was to tap the cylinder head , and run two extra coolant pipes back to spread the cooling load out across the cylinder head. I wonder if this is where GMH got the idea from? I'd love to see this done on your test motor, and see how it compares with the thermocouples to the super-dooper EJ gasket.

Cheers,
Harv

[ardiesse]

Harv,

Why thank you . . .

I can better understand the lumpy humpy trick of drilling the head and making a "coolant manifold" now.  It'd tend to equalise the flow of coolant inside the head, and perhaps most importantly, minimise the average path length that coolant would take between entering and exiting the cylinder head.  Are the holes generally drilled above the 2-3 and 4-5 exhaust ports?

To the best of my (scanty) knowledge, the modified head gasket 7424869 was never used in production.  I think it was one of those "hidden knowledge" things that Holden dealers had up their sleeves to fix overheating and cracked heads in near-new Holdens.  Coincidentally, when I got to Ceduna in 2012 with an overheating car, the guy in the next-door motel room had done his apprenticeship at a Holden dealer in the early '60s.  He said that there was a fix for the J-series motors involving drilling out passages and a different head gasket.  First I'd heard of it.

Yes, you're right.  You can fake the modified head gasket with the Teflon plugs, but you also need to take a drill to the head and block as per the fitting instructions.  For your meth monster, I'd suggest this cooling system fix as a minimum.  For a stock motor, it may not be strictly necessary to drill the passages out.  Blanking off the holes alone may be sufficient.  That's the idea I get from doing the fix on my "test" motor.

The original head gaskets were the double-shim asbestos sandwich type.  The 7424869s are of the same construction as the 2017 aftermarket head gaskets.  Which makes me wonder . . .  Rather than doing all the fiddly work with sheet Teflon and scissors, maybe one could go to the gasket manufacturer (AA Gaskets in Melbourne)with a normal grey head gasket and a 7424869 and say, "I'd like to get a special run of head gaskets made with these twelve punch dies removed."  It's just a question of cost and minimum production quantities after that.

Rob

[Old_Mt_Isa_Boy]

Might be worth asking the cost at least. Maybe Pete has an idea?

Regards

Wayne b

[hsv-001]

My older brother used external oil filter and transmission coolers behind his front spoiler on a fibre glass flip front FJ that was bored to 3 1/4 back in the day ,and I think it helped . Cheers Haydn

[Maco]

An interesting & great read Rob.

[graham_fuller]

Yes Rob very informative. Thanks
Cheers,
Graham