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Discussion Starter · #1 ·
Hi everyone, now that the weather is getting hotter in my country, I always keep an eye on the temp gauge just in case. My car is still being broken in, so I dont run it hard. The builder decided to remove the fan and put an electric one, with a fan switch screwed on the lower radiator tank.

Now, the tricky part is that the car does not overheat (needle almost always is at 80 C) but the fan is on a lot of the time!

Today I tested the temps with an IR gun and the top hose is at around 82 C.....now the strange part is that the lower one is at 85-86!! Shouldnt the lower hose be at lower temp than the top one??

My car seems to have a drop in thermostat. Below the housing there is a hose connection which is now plugged with a rubber cap. I see these cars can have a "bypass hose", I think I dont have it, could this be an issue? Otherwise there arent any other "capped" ports on the engine (waterpump has only 2 ports). The heater core is bypassed with an "U" pipe (as if it were always on)

Thanks in advance for any help and advice!!

cheers,
Demian
 

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For having a bypass hose you need a waterpump with 3 outlets and a euro drop-in termostat manifold, not screw-in. Where the U conects to the heatercore should be a T conection that conects, outlet of heatercore to inlet manifold and to the waterpump, so you are bypassing the system when the heater is not functional
 

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Discussion Starter · #3 ·
For having a bypass hose you need a waterpump with 3 outlets and a euro drop-in termostat manifold, not screw-in. Where the U conects to the heatercore should be a T conection that conects, outlet of heatercore to inlet manifold and to the waterpump, so you are bypassing the system when the heater is not functional
Hi Quadrifolio,

My water pump has 2 ports (I think my engine should use a 2 port pump) but the manifold is Euro or newer....that is why the lower port on the manifold is plugged.

Could this be the cause my temp is higher at the bottom? I mean, this car originally had a 2 port pump and no bypass at the manifold (and they worked for years)

I am also thinking, could the water pump pulley be too small somehow??

Thanks
Demian
 

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Demian, I would think that you heatercore is bypassed probably because is leaking (common problem), normally to fix that is a PITA, so people just bypass it to get ride of the leak, not having heater than. I wont think that that is the problem. All Alfa waterpumps have the pulie with the same dia, so thats not it, may your radiator be plugged up? what is the Temp. gauge showing? Here a pic of my ´69 Gt Junior. your hose routing should be the same, only I fit the proper screw-in termostat.
 

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So heater core is bypassed, where you get water pump inlet which normally come from heater? There might be too much coolant flow straight from engine head to water pump.
 

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" All Alfa waterpumps have the pulie with the same dia, so thats not it,"

Ummmmmm.......
 

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Discussion Starter · #7 ·
So heater core is bypassed, where you get water pump inlet which normally come from heater? There might be too much coolant flow straight from engine head to water pump.
Gasolina,

The outlet at the end of the manifold is connected with a hose to a U pipe (instead of the heater core) and another hose connects from the U to the water pump.

Today speaking with a mechanic friend we agreed that idling and at low speed, water could be taking that path (the one with least resistance) instead of going though the radiator. The heater core should cause resistance (if valve is open, if closed there is no circuit) and in my case, with an U pipe, the water goes from the top of the manifold to the water pump directly....instead of getting sucked from the radiator it gets sucked from the hot manifold....and pools itself at the lower part of the radiator.....until the thermostat cycles...

That is just our guess though.....:grin2: but it kinda makes sense.....so he suggested adding a flow restrictor to the hose going to the U pipe.....what do you think??
 

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Discussion Starter · #8 ·
" All Alfa waterpumps have the pulie with the same dia, so thats not it,"

Ummmmmm.......
Most alfa shops sell 2 waterpumps with different pulleys.....one for dynamo and one for alternator as long as i know
 

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Most alfa shops sell 2 waterpumps with different pulleys.....one for dynamo and one for alternator as long as i know
I always had the impresion that the diference in pulleys are the cranckshaft one (small for dinamo, big for alternator) and the dynamo/alternator ones, not the waterpumps being the only diference 2 or 3 outlets. (speaking about 105´s)

I think your right about whats happening, you have a dop-in termostat manifold wich have ONLY 1 outlet at the back instead of 2 of the screw-in manifolds, for using such manifold you NEED a 3 oulet waterpump to bypass the system correctly otherwise coolant could take the shorter route, thats why the screw-in manifold has 2 oulets at back, to force the bypassing when the heater is not in use, at least that was always my undestanding about it
 

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Gasolina,

The outlet at the end of the manifold is connected with a hose to a U pipe (instead of the heater core) and another hose connects from the U to the water pump.

Today speaking with a mechanic friend we agreed that idling and at low speed, water could be taking that path (the one with least resistance) instead of going though the radiator. The heater core should cause resistance (if valve is open, if closed there is no circuit) and in my case, with an U pipe, the water goes from the top of the manifold to the water pump directly....instead of getting sucked from the radiator it gets sucked from the hot manifold....and pools itself at the lower part of the radiator.....until the thermostat cycles...

That is just our guess though.....:grin2: but it kinda makes sense.....so he suggested adding a flow restrictor to the hose going to the U pipe.....what do you think??
I think you are on right track :) Screw-in thermostat manifold has in-built flow restrictor in short circuit outlet.
 

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I always had the impresion that the diference in pulleys are the cranckshaft one (small for dinamo, big for alternator) and the dynamo/alternator ones, not the waterpumps being the only diference 2 or 3 outlets. (speaking about 105´s)

I think your right about whats happening, you have a dop-in termostat manifold wich have ONLY 1 outlet at the back instead of 2 of the screw-in manifolds, for using such manifold you NEED a 3 oulet waterpump to bypass the system correctly otherwise coolant could take the shorter route, thats why the screw-in manifold has 2 oulets at back, to force the bypassing when the heater is not in use, at least that was always my undestanding about it
105-engines really had water pump pulleys in two different size, not sure if the small one carries 101 or 105 part#. Will check today ;)
 

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Discussion Starter · #13 ·
I always had the impresion that the diference in pulleys are the cranckshaft one (small for dinamo, big for alternator) and the dynamo/alternator ones, not the waterpumps being the only diference 2 or 3 outlets. (speaking about 105´s)

I think your right about whats happening, you have a dop-in termostat manifold wich have ONLY 1 outlet at the back instead of 2 of the screw-in manifolds, for using such manifold you NEED a 3 oulet waterpump to bypass the system correctly otherwise coolant could take the shorter route, thats why the screw-in manifold has 2 oulets at back, to force the bypassing when the heater is not in use, at least that was always my undestanding about it
thanks for the reply!

If the screw in thermostat manifold has 2 ports on the back, where does the second one go? One is for heater, and the other one??

My drop in manifold has 2 ports (one in the back and one not being used near the thermostat). In the later cars where this manifold is used, a 3 port waterpump is used. Isnt the water path of the bypass port similar in that case?? From manifold to waterpump directly?? (I understand this in theory helps with heat spots on the head when the thermostat is closed). But somewhere I also read this "bypass circuit" has a restrictor....

I am not willing to change my waterpump (too much hassle!) but would like to modify my "newer style manifold" so it works in a similar way to the original screw in thermostat manifold on the car......
 

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Discussion Starter · #14 ·
I think you are on right track :) Screw-in thermostat manifold has in-built flow restrictor in short circuit outlet.
Great! But as I posted above, the new style manifolds have a bypass directly from the manifold to the third port on the waterpump. Isnt this circuit similar to what happens in my car (circuit from manifold directly to waterpump)?
 

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Discussion Starter · #15 ·
Mmmm.....nevermind! watching the picture that quadrifoglio poster earlier above now I think I understand it!!! There are 2 ports at the back on earlier manifold, the one going to the heater (probably not restricted) and another port that is "T"eed to hose going to the waterpump (which as you said, is restricted).

So in order to have a similar circuit without the heater core in my car and with a 2 port pump, I should restrict the port on the back of the manifold. This way it will act as if the heater core is closed and a small amount of water will bypass from the manifold to the waterpump....

Am I correct??
 

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Yes, Correct.

Are you planning to use heater? If not, you can use water pump "heater inlet" as a bypass circuit from thermostat housing. Just need to be sure you have correct dual flange thermostat to control short circuit and radiator.
 

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Discussion Starter · #17 ·
I hadnt thought about that option.... I am not sure what thermostat is inside there. It seems to me that the port for the bypass has a larger OD than the water pump inlet though.....

Today I found a nice CNC piece in my toolbox to use as restrictor (6mm ID) and installed it at the hose coming out of the rear of the manifold....I am going to try it over the weekend to see what happens.....there should be some change (I think!)

Thanks again!
Demian
 

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Yes, water pump inlet is smaller than bypass outlet, it's not straight fit.

Thermostat controlled radiator bypass came with 1750 engine about 1968. My opinion is that the reason was taller engine, water gallery in head is upper level than the radiator. So no more natural way up for coolant flow which warmed thermostat for proper "timing". Bypass system fixed the problem.
The other good thing is all flow go through radiator when engine s hot, also engine get warm quicker.
But, in my opinion again, 1600 and 1300 are fine without thermostat controlled bypass.

I measured factory made restrictor, it was ID 5,5mm so you are really close. Good Luck!
 

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Discussion Starter · #19 ·
Hi gasolina,

today I took the car for a drive.....and still there is more heat at the lower part of the radiator than at the top! At least at idle or revving the engine while stopped....

I guess this is the way it should be (My theory is that this happens as long as the thermostat is closed) and originally this wasnt a problem because the belt driven fan was always spinning....in my case it bothers me because the electric fan turns on although the temp at the gauge is dead at 80 degress.....

Or...do you have any other suggestions?? such as ....leave it alone?? :p

thanks!
Demian
 

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Hi Demian,

Have to say that I am not measured temperatures in different part of cooling system. After looking at some fan temp switch values which seems to be surprisingly high, start 96 - 102C and stop 10C less, that is the way how it should be. Temperature inside radiator and all the cooling system can be higher than one can expect. Allways learning something new(to me) :)
My summary is that your system works fine, but keep bypass restricted, cause it means more flow to radiator.

Thanks,
Jorma
 
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