Author Topic: cooling system help  (Read 15840 times)

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Offline evannice

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cooling system help
« on: August 07, 2007, 02:24:12 am »
Hello,

My 1300/124 is boiling all its coolant out the upper hose that goes between the external thermostat and the coolant header tank, you can see the setup in the attached photo.  With the "radiator" cap on the tank, coolant goes out the overflow pipe onto the ground when operating temperature is reached.  With the "radiator" cap off the tank, it just boils the coolant in the upper hose and splashes out the top. The car runs and drives very well, no smoke or steam out the exhaust, the front radiator hoses get hot, as does the heater core.  As I have done with 124 TC cars with closed systems and overflow tanks, I have bled it all carefully several times but no help.  What's my next move?  Trouble shoot the thermostat and water pump?  Thank you for any advice and experience.

Eric, San Diego

Offline zippyfiat

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Re: cooling system help
« Reply #1 on: August 07, 2007, 05:30:55 am »
Hi Eric, I think you still have air trapped in the system.  I am not sure on the correct procedure to deal with this, and defer to one of the experts here.  Your engine bay looks pretty nice.  I hope mine looks like that some day!

Gil

Offline Pantdino

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Re: cooling system help
« Reply #2 on: August 07, 2007, 06:33:34 am »
Hi, Eric,

What temperature is the coolant that's coming out, or what is the temperature of the hose or tank from which the coolant is boiling out?   In other words, is the coolant coming out because it is above its boiling point, or is the system over-pressurized from something else? (Like a blown headgasket leaking high pressure gas into the system.)

Is the radiator cap the correct pressure?  If its too weak the coolant may boil out at a lower temperature.

How did you bleed the system of air?  Does the front radiator have a bleed screw?

Jim Oddie

Offline evannice

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Re: cooling system help
« Reply #3 on: August 08, 2007, 06:56:03 am »
Hi Gil and Jim,

I too think it's behaving most like there's unpurged air in the system somewhere, so I'll have another go at bleeding it out and try a higher PSI cap before tearing it apart again.  It is a 10 PSI cap right now.  I have heard that 12 to 13 is okay and 14 is pushing it.

There's no problem until it has been running for a while and is good and warmed up, then coolant comes out of the header tank steaming hot.  There is a bleed fitting on the upper portion of the front radiator, and I have been told there is another on the heater core which I have not yet found.

I don't think it's a head gasket or cracked head or block, because there is no oil in the coolant and vice versa, there is no smoke or steam from the exhaust, the compression tests out fine, and the plugs look fine.  And it really runs well.  But I sure would like to fix the problem before it leads to such disasters!

Thanks for your thoughts, there is no diagram and explanation of how this goofy system works that I have yet found.  It most closely resembles the external T-stat found on late '70's 124 TC engines, but with an extra bypass hose grafted on.  Another owner said he put on a BMW 2002 T-stat and simply blocked off the extra hose.

Eric, San Diego

Offline viotti600

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Re: cooling system help
« Reply #4 on: August 08, 2007, 08:34:23 am »
 The metal expansion tank is supposed to vent excess pressure &/or coolant out of the small open-ended hose when the system is hot, similar to the tank on a Fiat X1/9. When the system gets hot & the coolant/water mix expands, the tank's radiator-style cap dumps out the excess pressure via the small hose that points towards the ground. Technically, it is not a coolant overflow/recovery reservoir like the standard 850 plastic tank. It's more like the set-up on a Fiat 600 radiator, which has just a small dump hose connected to the radiator cap neck/fitting on top of the radiator, with the hose running down the side of the radiator & dumping excess coolant onto the ground.

 If your 1300 cooling system is topped-off full, then you run the car up to temp & the system vents a bit, that would be normal (should not be a huge amount of coolant lost, though). Let the car cool down (say, overnight), then without refilling the system, run the car back up to normal temp & see if the system stays even (doesn't vent coolant out). If it stays even, you're fine. If it doesn't stay even (continues dumping lots of coolant), there may either be air trapped in the system, or you may have a leak somewhere letting air in & causing the coolant to boil (system is not holding normal pressure). On 850's, 99% of the time it's a faulty cap or corrosion/damage around the opening for the cap (your cap looks new, but I just wanted to let you know this). ;)

 You might also want to check your pipes for any pinhole leaks. Easy way is to run the car up to temp, then keep the car idling & put the front of the car up on ramps, crawl/slide under & inspect pipes. This way your system will be under pressure & any leak(s) may be easier to see/hear.

There is a bleed fitting on the upper portion of the front radiator, and I have been told there is another on the heater core which I have not yet found.

Bottom left corner of this photo:
« Last Edit: August 08, 2007, 07:58:37 pm by viotti600 »
Jeff Stich
Norco, CA, USA

Offline grant gauld

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Re: cooling system help
« Reply #5 on: August 08, 2007, 12:23:31 pm »
When bleeding my OTS and OT 1300/124,when all is in good condition,i also raise a couple of feet the front of the car whilst bleeding the front and same same for the rear.Also pay attention to the heater (under the dash) as this has a factory position for the bleeding process also.It certainly looks/sounds like its just air as you have been very thorough so far.Well done with your cars prep so far,looks fine !.Grant

Offline evannice

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Re: cooling system help
« Reply #6 on: August 09, 2007, 01:48:54 am »
Okay, I removed the T-stat and boiled it up in a big pan.  It stays slammed shut at all temperatures up to 100 C.  I have a new one on order.  Hope it's that simple!

Eric

Offline Pantdino

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Re: cooling system help
« Reply #7 on: August 09, 2007, 04:13:46 am »
Certainly sounds like the thermostat is out of spec.  But you said the  radiator and hoses going to it get hot.  Why would that be if the t-stat were staying closed?  Is there a bypass hose, so some coolant goes to the radiator even when the t-stat is closed?

Jim

Offline evannice

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Re: cooling system help
« Reply #8 on: August 09, 2007, 05:39:46 pm »
Hi Jim, I am still scratching my head and looking sideways at this system, but yes the radiator is still in circuit with the T-stat closed, and heated coolant exiting the cylinder head has a big pipe right to the header tank and therefore the radiator circuit.  The lower section of the T-stat housing is one chamber with a big pipe to the radiator, the smaller bypass hose to the header tank (and then on to the other side of the radiator), and the return to the water pump.  So even with the T-stat closed, the radiator is in circuit.  The separate top section just goes to the cylinder head outflow, so when the T-stat opens, the cylinder head outflow is allowed to join with the rest of the circulation via these additional paths.

Not what I am used to, but I hear it works fine when everything is right.  Here's hoping a new T-stat fixes the problem.  Sure is fun to drive!

Eric, San Diego
 

Offline evannice

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Re: cooling system help
« Reply #9 on: August 13, 2007, 05:53:40 am »
Okay, I got the BMW T-stat today and it is the system I'm used to seeing on the 124 TC motors with external T-stats:  When cold/closed, coolant flows from hot engine back to water pump, and the path to the radiator is blocked.  And when open/hot, the path from hot engine back to water pump is blocked and redirected through the radiator.

There is no provision for the bypass hose, but I don't see a problem with eliminating it, and another 1300/124 owner has told me his car works fine without it.

So the old T-stat was essentially stuck in the hot position with the radiator in circuit.  So I am still pondering why it was overheating.

Offline evannice

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Re: cooling system help
« Reply #10 on: August 13, 2007, 06:07:44 am »
Sorry, I thought those sketches would post in color.  They are clear as mud.

But my other thought about why this wasn't working well, is that perhaps the water pump is not the reversed impeller type.  Now I have been told that those of you who make your own 850's with 124 engines in them don't think the reversed water pumps are important.  But in looking at my car while it is running and I have the radiator cap off, I can see that the pipe returning coolant from the radiator to the cylinder head (assuming for the moment a reversed flow) is at the very top of the header tank, and therefore would be expected to suck air at times.  Maybe you guys who roll your own are not using header tanks with this configuration, and so do not have this problem?

So I just went out and ran the car until warm and bled the system well, and verified that the radiator pipes from the exhaust side of the engine (and then on to the bottom of the radiator) get warm, while the pipes from the header tank (and then to the top of the radiator) stay cold.  And I'm thinking that either I didn't run it long enough to open the T-stat and the pipes got warm just because they're under the exhaust, or the water pump is not the correct reversed impeller type.

I'll get it out and drive it around more this week and see if the problem is solved or not.

Eric, San Diego
« Last Edit: August 13, 2007, 06:09:03 am by evannice »

Offline zippyfiat

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Re: cooling system help
« Reply #11 on: August 13, 2007, 03:55:02 pm »
Hi Eric, I am watching your posts intently to see that I don't eventually run into the same problem!  I WAS wondering if a BMW thermostat would work.  I have a BMW 2002 with what looks to be very similar thermostat to the Abarth item.  Is the one you have from a 3-series (or 2002) with M10 engine then?  I wonder if you could weld on the return pipe fitting?

I have also heard from various sources that a stock 124 water pump works fine in reverse rotation.  I seem to recal Greg Schmidt saying that a Toyota impeller can be made to fit on a 124 pump, but I don't think he said which model of Toyota.  If you ever find out, let us know!

If you haven't already, I suggest contacting Mahlon Craft or Oscar.  I would also suggest still pursuing the possiblity of air in the system.  I remember when I installed a front rad. on my old 600 Abarth replica, that I had a lot of trouble getting the air out.  And, FWIW, the 850 water pumps seem to run fine in reverse also, even with a front radiator.

Gil

Offline evannice

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Re: cooling system help
« Reply #12 on: August 14, 2007, 01:36:10 am »
Hi all,

It is sunny and 85 F here today and I drove the car around for maybe 30 minutes just now.  Warmed up rapidly, all the pipes got hot, heater and radiator got hot, temp gauge never got over the 1/2 mark in the operating range, cooling fan never went on.  Road & Track said theirs didn't either, and Oscar says the same for his car.  It passed a fair amount of overflow when I got back to the garage and let it idle, but not as much as before.  Problem may be solved.

Gil,

The BMW thermostat is listed as fitting the 2002 and some other models as well.  It sure looks like you could drill an additional hole and braze or weld an outlet for the bypass hose.  That's not in my reportoire!

I see that some of the historic photos show the in-head thermostat system, and that is my preference based on several assorted front-engined 124 cars owned and driven and taken apart and fixed up.  There are fewer hoses and clamps and the T-stat is cheap.  Together with a functioning electric radiator fan and a true coolant recovery system, those cars will idle in hot weather traffic and never move off the 185 F mark.  If you have a choice with your car, that's my vote rather than messing with this external T-stat style.

And WOW is this a fun little beastie to drive!  All low to the ground and tight steering and oversteer if you want, and all that smooth torque, and the sporty exhaust note.  Still needs a few things, I do believe that a nice set of seat belts just rose to the top of the "to do" list  :-)

Eric, San Diego

Offline evannice

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Re: cooling system help
« Reply #13 on: August 14, 2007, 04:37:45 am »
Hah, so much for the fun.  The heater core bleed fitting just twisted right off.  Looks like it was badly corroded, and I bet it was letting air in while the system was cooling, and then the air expanded and belched out next time it heated up.  I'll pull it and see if it can be repaired, perhaps I can get someone to put in a brake fluid-style bleeder fitting.

Good news: seat belts are in.  I was pleasantly surprised to find threaded anchor points already there and waiting!

Offline Pantdino

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Re: cooling system help
« Reply #14 on: August 14, 2007, 07:18:57 am »
Hah, so much for the fun.  The heater core bleed fitting just twisted right off.  Looks like it was badly corroded, and I bet it was letting air in while the system was cooling, and then the air expanded and belched out next time it heated up. 

I doubt that very much, Eric.  If there had been a leak there it would have been allowing coolant to drip out, as the system is pressurized when hot to almost 1 atmosphere above ambient pressure. 

I have heard that air in the system can do weird things.  When you bleed the system, do you do it with the rear end raised?  I always change the coolant in my Ferrari 246GT and Pantera with the front wheels in the gutter and the rear in the driveway, or an equivalent rake in the garage.  This causes air to stay in the engine and header tank.  After draining the radiator I add coolant to the header tank by the engine until no more air comes out the bleed valve at the top of the radiator, then I close off the bleed valve.  Then I add coolant to bring the level in the header tank up a bit, but not full.  Then start the car and as it warms bleed the radiator a few more times to let out any air that gets trapped there.  When it is fully hot and no more air comes out, you are done.  Just remember to check the header tank level after it cools and top it up to where it should be.

In both of my cars the header tank is higher off the ground than the radiator, so they are less likely to collect air in the tubes that run between them than in a 1300/124, I would think, because the radiator is fairly high up.  You may want to try bleeding with the car at a pretty steep angle so the air in the horizontal tubes comes out.

I haven't changed the coolant in my new-to-me 1000TC replica yet, but it's radiator is pretty low also.

Jim

 

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