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The next test drive is for the mechanical fan and shroud reinstalled, and electric fan removed.

This will prove that this change is causing the problem or not.

This is what you need to work out, before moving forward again.
Pete
 

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The sensor has to be pretty cheap. It's worth a try. There has been a lot of 'advice' on this issue since I last checked...I have a much later Alfa, an 86 S3, but except for fuel injection I have the same setup as you, including fresh head (1yrs ago). The stock fan, new, granaded when I hit a dip in the road. New motor mounts were...what we all get when we order motor mounts. E-fan does just fine, using a relay and a sensor screwed into the lower left corner of radiator. Turns on when temp gauge is just over 175 mark. My fan is a puller in back of the radiator, just like yours. I'm running Prestone and some old Sierra I found (didn't buy enough prestone) and just replaced the radiator with a used one in March due to leaking.

I think that you might be OK. I'm hoping that you saved the Evans, as that stuff is expensive but it does the job fine, and you can re-install it later after purging your system. I still haven't installed mine, as I'm saving it for my 74 TR6, and I'm waiting for the small leak in the radiator to become worse before I replace it and purge the block. I've not met anyone in the British car shop that has an issue with Evans.

I don't have a shroud for the reasons that you don't have one. I hate to offer any more confusing advice...but I like the earlier advice given about checking your fuel mixture. You will find the issue, I'm sure! We always do. :smile2:
 

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Discussion Starter #63 (Edited)
Have you investigated the chance the temperature gauge might be off? I read you had an infrared gauge check the readings- I've had inconsistent results using an infrared gauge.
Using the infrared device, what is the temperature of the lower radiator hose when the upper hose is reading 200/210 ?
165-170F — Touching the bottom hose confirms it is significantly less scorching then the top one, but still plenty hot.

I would be happy to dismiss it as an inaccurate gauge except that it always pointed straight up until the recent work.

I’m this close to throwing in the towel and just ordering a new radiator and thermostat.

Still can’t shake the feeling that it could be an air bubble somehow. The temperature needle moves under cornering which it never did before, but nothing except a steady stream of coolant comes out the bleeder screw.
 

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That's a large difference between top and bottom hose temperatures-10 or 15 degrees is normal, often less than that. Try and additional ground to the engine near the temperature sensor. It need not be a large wire but should have a good connection at each end.
 

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Discussion Starter #65
I don't have a shroud for the reasons that you don't have one. I hate to offer any more confusing advice...but I like the earlier advice given about checking your fuel mixture. You will find the issue, I'm sure! We always do. :smile2:
Thanks for the support!

The carbs have not been ‘jetted’. They are fresh from the rebuilder. Could incorrect jets alone account for these higher temperatures (~20-30F)?
 

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Increased power and/or lean mixtures will create more heat that has to be transferred through the radiator. A stock radiator in good shape should be good for at least 150 HP with correct mixture. My radiator became marginal when the power got up to about 170 HP.
 

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Increased power and/or lean mixtures will create more heat that has to be transferred through the radiator. A stock radiator in good shape should be good for at least 150 HP with correct mixture. My radiator became marginal when the power got up to about 170 HP.
Reading through your thread, it looks like you replaced the head but I did not see any mention of performance oriented changes. Is that correct? Is there a reason you would expect the carburetor jetting to be incorrect? I recently saw a temperature increase of 20 degrees F after significant engine changes and before increasing the idle jet size. This was during the 30 minute cam break-in process. I am running emissions Dellortos (DHLA 40L) and changed from 57 to 65 idle jets, which brought the temperature back down to 180 degrees (and eliminated spit back).
 

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Discussion Starter #68
Reading through your thread, it looks like you replaced the head but I did not see any mention of performance oriented changes. Is that correct? Is there a reason you would expect the carburetor jetting to be incorrect? I recently saw a temperature increase of 20 degrees F after significant engine changes and before increasing the idle jet size. This was during the 30 minute cam break-in process. I am running emissions Dellortos (DHLA 40L) and changed from 57 to 65 idle jets, which brought the temperature back down to 180 degrees (and eliminated spit back).
The cylinder head is from Centerline. They offer a plain head and a performance one. This is the plain head, but Centerline told me it does have some mild improvements over stock. The cams are original.


"Centerline’s remanufactured cylinder heads will put the ZING back in your Alfa! Each head is meticulously inspected for cracks and other damage. Those that pass are treated to all new valves, manganese-bronze valve guides, teflon seals on intake and exhaust guides, and our performance valve springs. A careful multi-angle valve job is performed to ensure peak airflow and performance, and each head is resurfaced for optimum head gasket sealing."​


I don't know much about carbs. I removed the carbs from my car, took them to a reputable rebuilder and asked them to rebuild them for an Alfa 2L. When he handed them back, he said they'd run but would need fine tuning. It's been my understanding that carbs should always be jetted to the specific engine they're mounted on, which can only be done after installation. But I've heard conflicting opinions so I'm not sure if that's true. I have not (yet) had any such tuning performed.

And I *am* getting some spitback!

Could carb tuning be the cause here? The first carb specialist I called said no way, but I don't know what to believe anymore.
 

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If the carburetor jetting worked with the old head, it should work with the new head. I interpret fine tuning to mean synchronizing the throttle plates of the two carbs and setting the idle mixture screws. This needs to be done and should reduce or eliminate the spit-back but I am not confident these adjustments will impact your temperature issue.
 

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Discussion Starter #70
If the carburetor jetting worked with the old head, it should work with the new head. I interpret fine tuning to mean synchronizing the throttle plates of the two carbs and setting the idle mixture screws. This needs to be done and should reduce or eliminate the spit-back but I am not confident these adjustments will impact your temperature issue.
I guess I assumed that new jets were put in the carbs without much regard for what was in them before.

I should've asked, but it's too late now.
 

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If you have any doubt, remove the plastic covers and the jet holders and see what you have. Very straight-forward but you may already know that.
 

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i posted here( I looked around) a modded out t-sat housing, cut the the working parts out?off got a new t-stat from a other car, and dremeled out a new place for the working pasts of a t-sat to work.. this way you could use any temp that you wanted.. even posted photos
 

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Good luck. I'm out. There is absolutely no logic in your problem solving, just a ton of random ideas. That is not how you find causes and then resolutions.

You have to follow a path until it is 100% confirmed the wrong or right path ... you still have not confirmed if it is the change from mechanical to the electric fan that is the cause.

Again, good luck. Hope you accidentally find a fix.
Pete
 

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Thanks Pete. I quit responding to this thread when I brought up some simple issues that needed to be addressed before looking for some abstract reason. I still believe it is the fan, which I suggested he confirm before going further but he is "sure" it isn't the fan. Those electric fans can be set up to push or pull, requiring flipping the fan and reversing the wiring to spin the opposite direction. Very simple to establish whether the airflow is in the proper direction. Quit searching for some fragmented possibilities and go back to basics.
 

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Discussion Starter #77
Good luck. I'm out. There is absolutely no logic in your problem solving, just a ton of random ideas. That is not how you find causes and then resolutions.

You have to follow a path until it is 100% confirmed the wrong or right path ... you still have not confirmed if it is the change from mechanical to the electric fan that is the cause.

Again, good luck. Hope you accidentally find a fix.
Pete
I think if you look past the fact that I haven’t followed your specific recommendation, I am following a logical process of problem solving.

Blaming the fan seems to me like the least likely explanation, since the problem persists at 70 mph and, 1970s Aston Martins notwithstanding, I can’t see how a 70 mph breeze can fail to match the cooling power of the prior mechanical fan with shroud.

And since I don’t have a mechanical fan or shroud to try anyway, I am, for now, ruling out the other possibilities because they are comparatively easier and cheaper. Confirming mixture settings and thermostat type doesn’t seem random to me, since both of these variables were changed at the same time as the fan.

Whatever. I am grateful for the advice you provided, and may yet follow it.
 

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Sorry, I thought you still had all the mechanical fan bits. Hard to test reinstalling them without them ... lol

Best
Pete
 
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