On the face of it, it certainly looks like a blockage. Unlikely that foreign matter has entered the water system, but it could be that a part of the car has come loose - perhaps from the heater or some other waterway?
I would persue the 'low return water flow' problem and try to isolate exactly where the low flow is occurring.
One thought on removing the heads - what state is the car in now? If it's still largely dissassembled due to the water pump being removed, then this will account for more than half of the labour charge to remove the heads, so you the additional cost may be less than you think.

Sorry I cant be more help. Post an update on Monday.

 

We don't have those cars here and I have never even seen one but after years of working on Alfas I will chime in anyway.

I am not clear about just when this happens. Will it overheat if you start it and let it idle. If not does it seem to be related to speed? If it doesn't overheat sitting still but does when you drive it then it's probably a blockage in the radiator or thermostat. If it will overheat idling it probably the thermostat or the fans.

1. This really sounds like a thermostat issue. I would change that out regardless of the fact that the mechanic thinks it's operating correctly.

2. I have never heard of a cooling system blockage this severe inside the motor. It's FAR more likely to be in the radiator. I just don't see any reason to pull the heads.
Greg Gordon
www.hiperformancestore.com

 

Hi,

There is an issue on the water pumps that these engines have.

The fan of the pump is made out of plastic and although the pulley rotates the fan won't as it slips against the shaft.

The symptoms for a failed water pump is lack of coolant circulation meaning low temps at the radiator hoses and no coolant flow to the coolant expansion tank via the small diameter hose.

I also doubt about engine block blockage...

You don't mention if the water pump was removed, inspected out of the car or renewed. When the car overheats have you grabbed the radiator hoses to feel their temp?

Regards,

 

Is there a remote possibility that the radiator fan is running backwards? I had this happen to my old Milano (75). My fan connectors were replaced, they were reversable. Once after service work overheating followed, the wires had been reversed. This would never happen by itself, we are talking human mistake.

When the fans blow backward, the car works fine at idle. On the road, the fan offsets airflow which leads to overheating. At speed the airflow might overtake the fans, yet it would be insufficient for proper cooling.

Ken

 

Going off what was check, and assuming the mechanic is correct, heres my advice.


I'm not familiar with new alfas. But as a BMW mechanic, dealing with, and also having a similar situation, maybe my advise will help.

First off. Is the arrow on the thermostat pointing the right way (usually up)? Is it in the right way? Find out where Alfa likes it.

Have them pressure check the system cold and hot. At least up to 20psi.
Watch the gauge, and inspect all hoses, reservoirs, etc while system pressured.
remove valve covers (while cooling system pressured) and inspect to see if any of the heads are cracked up top (if there is a crack, you'll see a clear line on the head with oozing coolant, but the cooling system must be under pressure, when inspecting). Maybe even pouring a engine leak check fluid in the oil, or radiator.

Compression check, and Leak down test.

I think the inlet is not returning water, due to the thermostat not opening all the way. reason the engine overheating. Not necessarily saying its a bad thermostat. there is a leak else where which is causing the coolant to escape, and the engine is overheating so quick, that there's not enough heat once gone through the radiator to the thermostat to open it, and if you wait till it does open, then you'll be purchasing a new motor.

How about removing the thermostat completely and then checking if the engine overheats? If it doesn't then I'd say its the thermostat, which is bad, or not installed properly. If it does still overheat, then theres definitely a problem in the head/s. Gasket, cracked head, and

p.s. if it doesn't over heat with the thermostat out, then you can drill a hole in the thermostat (assuming the thermostat is good, and the problem is in the head), and more then likely be able to drive the car around with out it overheating. I don't recommend it, but if moneys tight, then you have to do what you have to do. I've seen it done in the past with good results.

keep us posted.

 

The Alfa V6 requires a thermostat for correct coolant flow. The thermostat is very common cause of cooling failure. Verify that the thermostat works properly, even though it is new.

An infrared temperature sensor is most useful for monitoring coolant flow.

 

The Alfa V6 requires a thermostat for correct coolant flow.

Huh According to who?
IMHO opinion you can take out the thermostat (inside the housing) of both the 12 valve and 24 valve V6. The coolant will constantly flow through the radiator in this configuration. Had a milano/75 2.5 V6 this way, and also a 3.7 V6 24 valve race car without thermostat.
Jes

 

Jes,

Maybe what Ken meant was for the flow to be correct in order to maintain a certain temperature (185-195F).

The thermostat is not needed if you don't care for the temperature your car runs at, and its absence will not overheat the engine. The problem is in cold weather the engine's temperature might be too low.

My 164S has no thermostat (for now) and it runs cooler (than it needs to) in winter.

 

Ok. I read the post as saying the flow (as in direction) will be incorrect, and hence could result in overheating. As you say, taking out the thermostat will provide full flow through the radiator (max cooling) at all times. This is too much cooling for a street vehicle.

Appologies for misunderstanding. Though, I have seem such claims elsewhere.

Jes

 

I had a cooling problem once that I attempted to solve short term with no thermostat. It did not help, possibly worse. More than anything, I respect direct observations rather than theory. Your experience without a thermostat speaks for itself. My Milano cooling problem must have been from a failure to purge all the air from the system after a having the heads off.

 

A vehicle that has a ECU would tend to run rich if it never reaches operating temp.

 

If it has no thermostat,block the bypass....preferably run a thermostat.
BLEED THE SYSTEM PROPERLY! There is a bleeder behind the rear head at about cyl # 3 area-REMOVE the front top radiator hose when filling up and bleed the air from the upper hose.Air here cannot go down to the engine and is then trapped in the hose and radiator.
Its easy to check if the water is circulating on these cars...The fan will blow hot when switched on and the radiator bottom hose will warm up-logical.
If this does not happen and the fan switches on,no water flow!

The fan switch goes hot with an open circuit..

Radiator cap is a weak item on the 156..replace with the green high pressure type from the GTA...

My bet is the waterpump impellor as already stated...I replace them with the cast impellor from the gtv6 pump.

Dont rush the bleeding process..do it as I described and wait for the thermostat to open and fill the header again before sealing the system..

 

"I think the inlet is not returning water, due to the thermostat not opening all the way. "

A thermostat opening 8mm is more than enough to bypass water.When its cycling water it rarely opens more than 2 or 3 mm..Its the time that its open and cycling water thats important,not the distance it opens..

Remember that it will first block the bypass before opening to cycle the water..These 2 operations happen within a few deg c,as in 2deg or so..

 

I have a very similar issue with a 3.0 24V 166. One exception is that my coolant does not overflow. I do smell coolant in the garage after parking. I can produce a temperature spike under acceleration at 80 MPH or better. Oddly, the temperature spike to max hot immediately goes back to 90 C when the engine is stopped and the key is turned back on. Replacement items include thermostat, temperature sensor, and radiator.

GRITSOP posted that the water pump impeller is sometimes known to be loose on the shaft. I now suspect that this is my problem and it is plausible with the 3.0 GTV.

Ken

 

The parts guy at the local Alfa dealers told me that the GTV uses a steel impeller wheras the saloons use platic. I can confirm that my GTV does have a steel impeller. I cant see this comming loose on the shaft the way a plastic one might.
On a side note - does anybody have the part no's for the GTV water pump, and for those of the other 24v v6's?

 

- does anybody have the part no's for the GTV water pump, and for those of the other 24v v6's?

Yes, the 916 GTV and Spider 3.0 water pump is 60668486. While 60668487 applies to Kappa, Thesis, GTA, 166 the GT. I speculate that the difference between these pumps is the shaft length.

If it is any consolation, I understand that Ferrari also use plastic water pump impellers.

Best regards,
Ken

 

116 gtv6-steel impellor

new gen gtv 30 24v-plastic impellor

 

I have been reading 156.net and there are many people stating that 3.0 24V GTV has metal impellor, which should also fit to 156 2.5 V6 (original plastic one).

 

Here is a comparison from the ePer parts CD. The 166 version is listed first with a replacement seal, item 9. The 916 GTV is shown next, one can observe a huge variation in the shaft length. Interesting because I had thought that most everything had been standardized between these cars. This is unfortunate, I own both a 24V 166 and a 24V 916 Spider, it would have been nice to have a single water pump on the shelf as a contingency.

 

Although the line drawings are quite different, all other pulleys share the same part numbers. I would really like to see a physical comparison of these two pumps. Why would the 916 be different from all the other late model V6 water pumps? The drive pulleys are fully standardized. The following drawings show the 166 and 916 3.0 engine, all parts are identical, with the exception of the water pump.

 

okay maybe they are wrong there... anyway thats not big problem if you change also the pump with every second belt change or just get metal one

 

I conferred with Mangoletsi today. They think that a water pump is the problem on my 166 overheating spikes. Also, there is a new and improved part number, 55198357. This would apply to all late model V6 engines except the 916 cars. Just my opinion, that one must be an optimist if your an Alfa owner. I am optimistic that the new and improved water pump will have metal impellers. I will be holding my breath waiting for the parts packet to arrive.

Ken

 

Anyone know what has happened to Gvirmacati who started this thread??
We are all throwing ideas around here,Im waiting for an update from this fellow and he`s dissapeared!

 

Hi all,

Wow! i go away for a few weeks and all of a sudden i have so much input into my problem! Thankyou to all who replied to this issue... It had me sweating for quite a while and im glad to say that the heads did not require removal!

I ended up getting the mechanic to take out the throttle body housing and found that the water hose that cools the throttle body was clogged. I got him to blow some compressed air into it and low and behold, a blob of sludge shot onto my suit pants... This hose is meant to return water to the reserve tank and is the highest point of the water level. Apparantly the mechanic found another passage which was blocked... but he only told me about this after i found the initial blockage... so im sceptical at the truth to this... I think he just wanted to make sure i didnt take him to consumer affairs or something.

The car now runs colder than i have ever seen it... while cruising it barely goes above 50 while in traffic it sits just below 90. I reckon the owner who had the car before either never replaced the coolant or changed the type of coolant (this can on rare occasions cause sludginess if the different coolents have a chemicals reaction)

All in all, this escapade cost me $2200AU and this was due to a single clogged pipe... I guess the really really really frustrating thing about all of this is that the mechanic was ready to take my heads off (after already replacing my radiator and water pump for no reason). And if i had not had any mechanical knowledge i would be up for a hell of a lot more $$$... The heads would have come off to which they would then have found that the heads were ok... they would then at some stage stumble accross the cause... but i seriously doubt they would have told me that a small hose cost my engine to be dissasembled completely...

I guess in a nutshell i'm upset at that an alfa certified service center was about to remove my heads... and were going to charge me for it as well... Its sad to say but i find it always the truth, if you want something done, your better off duin it yourself...

Again thankyou to all who had input on this... and i hope this will save some poor bast@rd form going through the same heart ache as i.

cheers,

Gian

 

while cruising it barely goes above 50

That is too cold. I bet you need a new thermostat after all - it appears to be stock open, ironically
Jes

 

Jess,Thats actually correct on these cars...
You will find that out on the open road it will run at 50/60 odd degrees..
As you come into town,start stop traffic,it will go up to 90 and the fan will start cycling...
Some cars here will cruise at 80 and then go up with traffic conditions...

Strange,I know...

 

Jess,Thats actually correct on these cars...

Wow, really? 50C sounds very low. Guess I have been deprived of new Alfas for too long...
Anyway, thanks for pointing that out Barry!
Jes