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Discussion Starter · #1 ·
Dear Montreal enthusiasts,

Since summer last year I am the owner of a Montreal of 1972. During test drives of 15-30 mins the car was running without issues. When I extended to 45 mins plus I discovered bubbling of the cooling fluid in the expansion tank. The car has been at 2 Alfa shops now, gone through several tests and we still have not been able to indicate a root cause of the bubbling behavior.

Below I present an overview of all checks done and associated findings:
  • Cooling system cleaned with Bardahl
  • Fan and thermostat checked on function: good
  • Thermostat cap renewed: tighter spring version installed
  • Cooling fluid checked for exhaust gasses: none
  • Motor oil checked for cooling fluids: none
  • Radiator effectiveness tested: very good
  • Cylinder walls checked with endoscope for boiler scale presence by: very clean, just some corrosion
  • Engine is running very well, no white smoke whatsoever and oil and water temperatures are good also after long drives (the engine is not overheating)

The mechanics of both shops indicate that the head gaskets, neither head cracks can be the problem given their measurements and observations, but they do not know what is..

Any suggestions, advice, thoughts are very welcome to help solve this mystery

Many thanks,
Corwin
 

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Hi Corwin,

So sorry to hear of the issues with your Montreal. Unfortunately I have the same issues with my car and learned that the engine was rebuilt two or more years prior to my purchase. As I understand from my experienced Montreal engine re-builder, the same head gaskets (from MrFiat (or I believe Spezzio)) were used for another car and it exhibited 'fire ring deterioration'.

after a spirited drive I noticed the temperature gauge approaching 100C and coolant overflowing the reservoir when the engine was turned off, so perhaps the gaskets failed. When checking head nut torque only about 30 ft-lbs were required to loosen the nuts prior to oiling and re-torquing them. They were torqued to 67 ft-lbs or so as suggested in Montreal the Essential Companion but the bubbling continues. MtEC suggests other reasons for coolant loss but I believe you've checked off all of them. When performing the chemical 'Block Test' my engine was 'fine' -until turned off, at temperature, at which point bubbling became very pronounced and the block test chemical shifted to show exhaust gasses bubbling up out of the overflow reservoir. They could only come from the engine...

Despite the failed block test, there is no oil in the coolant or coolant in the oil. After each 30 minute drive or so, I check and use a radiator cap tester to pump coolant back from the overflow reservoir into the thermostat housing (with caps removed). If I didn't pump the coolant back into the radiator, eventually the coolant level would drop below the temperature sensor in the radiator, which would most likely prevent the fan from coming on and cause overheating. In my case, I know that at least the head gaskets need to be replaced. I have put off this major job for a couple reasons; mainly fear of the Spica and fear of finding heads that need expensive (crack) repairs. I have purchased new gaskets from "Gaskets to Go" and Reinz (I think).

Mark
 

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Discussion Starter · #3 ·
Hi Mark, sounds like 'we're in the same boat' wrt being left with no other option than to have the heads removed and check out what's wrong. I've heard stories from a reknown Montreal specialist (Fred van Lingen in The Netherlands) of cases where (very) small head cracks can cause the problems we are facing with our engines. They only reveal themselves when the engine is completely heated. I need to discuss now with my current Alfa shop what to do next and I'll keep you posted on the proceedings.

Best regards,
Corwin
 

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I think that the head gaskets or cracks is a likely cause for this overheating and just not showing up with a chemical block test for hydrocarbons in the coolant. If the Water Pump as not been rebuilt recently I would seriously consider removing the engine from the car and rebuild the water pump while the cylinder heads are removed.

I just finished dealing with a Triumph TR6 that could be driven around town for an hour without overheating but as soon as you started driving at highway speeds or in the mountains it would start overheating. The head gasket was not sealing well.

On another note here is a Gates part number for a 160 degree or 71 Cel. Thermostat for the Montreal engine

 
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Corwin, if you have not already tried it, it might be worth the effort to re-torque the head nuts on your engine. Shazz (Steve) had luck doing this on one or two of his Montreal engines. Also, Bruce Taylor states that "A minor gasket leak may cause a continuous stream of bubbles in the coolant reservoir when the engine is running. However, bubbles can also be caused by air in the coolant circuit if a malfunctioning filler cap valve prevents coolant returning from the reservoir to the engine after it has stopped" -this is harder for me to visualize but I understand that a malfunctioning cap or even a loose hose clamp on the return line would allow coolant to leave the engine but not get sucked back in when returning to room temperature. I understand that you've replaced the cap with a higher pressure cap. I did the same thing and it did noticeably increase pressure in the lines but the issue remains.

Ric, you are right. My car exhibits very slight bubbling while it is running but when the engine is switched off, the bubbling in the overflow increases significantly. If the coolant reservoir is more than one inch above the 'Min' line, cool; when hot the coolant will overflow the reservoir upon switching off the engine. (Page 103, in MtEC covers bubbling in the reservoir and compression testing)

Like Jeff suggests, if the engine is removed it presents an opportunity to up-date the water pump. I spoke with Delmas Greene last week and he strongly recommends the water pump modification Bruce describes in MtEC. Eliminating the highly stressed and complex loaded outer ball bearing (that is working at nearly 100% of its design load) on the water pump shaft and replacing it with a roller bearing -that has nearly 10 times the load capacity AND drilling a hole in the front cover as shown to allow lubrication of the bearing. Delmas has done this modification to 5 or 6 of his Montreal's and has not experienced a failure since; in over 25 years! (Pages 59 and 63).

Mark
 

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I have removed my engine and rebuilt it. What I originally thought was a Head Gasket failure turned out to be a Water Pump Bearing / Seal issue. If it comes to this, I suggest removing the engine and doing the re-build on the bench. But, before you go down that route, check your Cylinder Head Nut Torque. With the engine cold, loosen and re-tighten the Cylinder Head Nuts doing it in the "correct" sequence. I would Torque the Nuts to 65 ft/lbs first and then take them up to 70 ft / lbs. Leave overnight and re-check the Torque. If you still have the same problem, it's probably time to get the engine out. It's not such a big deal. There are a couple of threads here about it, so take your time and do it right. Some people may be worried about cracked cylinder heads. I would not jump to that conclusion right off the bat.
Yes, a good set of Head Gaskets make a big difference. They should not have been on the shelf for a long time. New Head Gaskets are available from Classic Alfa or Alfaholics in the UK. 3 days from time of order to delivery. Good Luck! By the way, do you have a Cylinder Head Nut Tool available?
 

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Discussion Starter · #9 ·
Dear enthusiasts, thank you for all your comments and suggestions. I’ve decided to have the engine removed and do all the needful to analyse what may be wrong and install proper, new head gaskets and upgrade the water pump bearing. I want to secure having a car I can drive for a decent couple of years without worries. Will keep you all posted on the next steps.

Corwin
 

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With the Water Pump it's not about any history. As a number of us know, the Bearings, Spacer and the Seal has been under stress for more than 40 years. It's not a matter of not failing, it's a matter of when it will fail. Unfortunate piece is that to remove the Water Pump and the Front Cover, you have to remove the Cylinder Heads. That is why most people will tell you to pull the engine out and rebuild it on the bench. This allows you todo the modifications to the Water Pump and the Front Cover, Cross Drilling the Oil Holes to better lubricate the Water Pump Bearing.
 
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