Replacement thermostat housings - Warning | FerrariChat

Replacement thermostat housings - Warning

Discussion in '206/246' started by TonyL, Jul 25, 2018.

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  1. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    Tony
    I just thought I should warn fellow Dino owners of the following tribulations encountered with my housing / pump replacement. My lesson not to take new parts for granted.

    After a routine service I noticed that the water pump had a slight stain from the bearing housing so decided to fit a replacement pump. After removing the thermostat housing things looked bad as can be seen from the attached photo, the aluminium just started to disintegrate.

    Ordered a replacement thermostat housing as this one looked beyond repair. 2 days later it arrived in the post and just fitted the unit with the thermostat it came with. Big mistake, I should have checked the quality.

    A small tutorial on how the cooling system works on the 246.

    The thermostat housing (TH) bolts directly onto the water pump but has three hose connections, the top one (front) is the return from the radiator, the next one down on the rear end is for engine recirculation (bypass) and the lower connection is the heater / expansion line. The flow to the radiator is from the upper nosing coming from the heads with a branch connection to the thermostat housing, middle connection (bypass)

    The middle (bypass) connection (TH) takes water from the cylinder heads / block via the upper nosing and circulates it through the pump and back into the engine so it can heat up quickly. Once up to operating temperature 82C the thermostat opens and shuts off the middle port and then directs the coolant to the radiator via the upper nosing and back via the oil heat exchanger and into the top thermostat housing connection.

    After letting the engine warm up I noticed the temperature starting to rise above 195 F 90C, the fans kicked in but the temperature continued to climb way above its normal operating band.

    Switched the engine off and started to fault find what has gone wrong, airlock possibly? Checked this through and all OK.

    Thermostat faulty? removed the front nose on the thermostat housing and to my horror discovered that the bypass face was just a rough casting (I am being polite) and didnt shut off the port properly causing water to short circuit around the engine block and heads

    It is critical that this seating is perfect for the thermostat to seal off the bypass circulation around the engine when the thermostat opens, otherwise it will short circuit around the engine and overheat the engine block / cylinder heads even though some of the coolant will pass through the radiator.

    The face on the original TH has a bronze liner which extends into the hose coupling, it looks like its pressed in or cast in with the housing. I guess they did this for two reasons.

    1. To get a good seal

    2. To ensure corrosion of the aluminium doesn’t corrode over time and not seal the hole.

    Decided to change the fan stat and replaced it with a Valeo unit 84C on 74C off, this is the correct one for the 246, the others sold on the market are too high, including my one!

    So my warning and to potentially save a cooked engine is to make sure you buy a housing that has a good machined face as an absolute minimum.

    Now here is the mystery, anybody ever noticed bubbling in the expansion tank, it caused a big concern as I initially thought it was a cooked head gasket. However after a few hours I blanked off the top small hose connection from the expansion tank and the bubbling stopped, released the clamp and it starts again.

    Revving the engine the bubbling stops as well.

    Tony

    PS did a hydrocarbon test and negative



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  2. pshoejberg

    pshoejberg Formula 3
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    Nice write up Tony. It makes me wonder if I have a leak the same place. My engine has Been running mysterious High since overhaul and i tried to change the thermostate with no effect. I Will check the housing after driving season.

    Best Peter
     
  3. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    Thanks Peter,

    The thermostat is set at 82C so should open up and shut off the bypass 100%, the temperature sender unit as you know is mounted on the front cylinder head.

    Although the radiator circuit is probably working OK, the sender unit is measuring a higher temp because the bypass isn't closed off properly. ie short circuiting
    I changed the fan switch and sender unit for the correct type as well, most on the market are too high. Some sell the Fiat X1/9 stat but that operates at a higher temperature than the 246.

    I spot checked the temps on the heads and rad etc and there was a big difference in readings. The Veglia gauges are crap really.

    Also make sure the thermostat is within the measurements of the original design, again most sell the Wahler or Behr units but the aperture is smaller than the original Savara unit (not made anymore) Make sure when your stat is open and has enough travel to close the opening. The Fiat 4222883 unit is close by the looks of it

    I have not done any extensive research into this (just a lot of head banging) but installing an original housing, the problem has disappeared albeit I have bubbling in the expansion tank when the cap is off. Its weird that the bubbles stop when you clamp off the top hose on the tank. I disconnected this thinking that air is being drawn in or air in the system but dipping the hose in a cup of water didn't show any bubbling from the system!!

    Best
    tony
     
  4. Eltel246

    Eltel246 Karting

    May 14, 2012
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    Hi Tony,

    What supplier did the replacment thermostat housing come from?
     
  5. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    I would rather not say at this point but dino parts in Germany appear to have well machined housings as do Eurospares in the UK. No bronze liner though, this is a photo of one of their units sent to me.

    Fortunately I managed to find an original, not in perfect condition but will do for now.

    With modern technology I would have thought these parts could be much better than the originals!

    Tony
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  6. Eltel246

    Eltel246 Karting

    May 14, 2012
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    I recently fitted one from SP. No apparent problems so far.
     
  7. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    Peter - Doing some investigations as my car temp gauge seems to be running higher than normal as well, seems a coincidence following fitting a new (after market) sender unit.

    I have found that the sender unit is not matched to the Veglia gauge. The reading at 195 is not correct. If you have fitted a new unit then this may be the cause of your problem as well. Trying to find a unit that matches but think the gauge and sender unit need to re-calibrated to suit.

    Hopefully it will be OK.
     
  8. pshoejberg

    pshoejberg Formula 3
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  9. TonyL

    TonyL F1 Rookie

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    What readings did you take / measure?

    The one supplied by SF is just a generic sender unit as I understand it so cannot possibly be a match for the VB gauge, a 10% error can make a difference further up the scale!

    Have you done a leak down test?

    Did you change the water pump?

    Do you have bubbles in the expansion tank when idling?

    Best Tony
     
  10. pshoejberg

    pshoejberg Formula 3
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    I am seeing up to +-100 deg C. Both the cooling water temp sensor and the oil temp sensor is purchased from SF. I now see from my old notes that I am running the oem 246 thermostat from SF as well. Looking at the SF website I see that there excist a specific thermostat for the 206, maybe I should be running this type in my early L-series? I wonder if there is a dimensional difference that could cause bypassing issues?

    Never done a leak off test on the overhauled engine and I have never observed the bubbles that you are observing. The waterpump is overhauled with an new impeller from DP.

    Best Peter
     
  11. TonyL

    TonyL F1 Rookie

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    my gauge always sat on the 195 mark and rose very slightly at standstill then the fans kicked in.

    Now it sits much higher with the new sender unit and unless the two are calibrated together then you will not get a accurate reading, you cannot alter the sender unit so will need to open up the water temp gauge and alter the coil pick up. I will send mine to speed cables as they are the experts in this field, I don't trust myself with this delicate operation! Infra red spot temp around the engine block and heads show average temp of about 87C so my gauge is about 10% out.

    Apparently the veglia gauges need the right sender unit and I don't think the SF ones are.

    The thermostat housing I think is the same for all 246 series cars, it was only upgraded from the early 2 litre 206. The fiat part number for the thermostat is 4222883 which was made by Savara, these are no longer made. I am trying to find out the replacement part from various thermostat manufacturer's and so sent a sectional drawing of the housing to them so they can advise on the correct part. From what I see, some of the specified units don't have enough "closure" travel when the stat opens and the secondary disc doesn't shut off the bypass enough. any leakage around this port will show up increased temps around the block/ heads. Still waiting for some replies?

    Tony
     
  12. pshoejberg

    pshoejberg Formula 3
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    I appreciate your hard work on this subject Tony! I have also checked my piston head and expansion tank temperature with a infra red instrument and it indicates too high operating temperature, so I am quite sure I have an issue. I can easily follow your thoughts regarding the sensors not being calibrated / or completely compatible with the old Veglia instruments, but it should be fairly easy to measure the sensor resistance and compare old with new. This will be on my to do list this coming winter.

    Best Peter
     
  13. Ken Ivey

    Ken Ivey Karting
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    Peter, I've had my '73 GTS for about 4 years now and the coolant has always run at 90c to 100c, the oil lags that slightly. The thermostat appears to open at 90 degrees and the temperature will rise a bit under load or in very hot weather. We put about 600 miles on the car this weekend during at a vintage rally - the weather has been in the high 90s. The temperature gauge stayed around the 100c mark and I was pleased because it was only a bit above the thermostat.

    Regards, Ken
     
  14. kjw9028

    kjw9028 Karting
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    I drove my 69 L series tonight and it was running pretty hot, got up to around 110 and the fans weren't turning on. This had happened last season so I purchased a replacement fan switch, the one that mounts at the bottom of the radiator. I had bypassed it and the fans fired right up. Any tricks to replacing the switch? Do the threads require any tape/sealer? I assume I'll lose a bunch/all of my coolant? What do you recommend as a replacement coolant? Thanks.

    Ken
     
  15. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    Ken

    Make sure the new stat operates in the range of 84c on, 75c off, the Valeo 819749 switch is perfect for the 246 engine.

    You should not loose to much coolant if you are able to do a quick changeover, I lost about 1/2 litre if you prep up the new one before. Use a good thread sealant on the face of the washer butting up to the rad face. They are a parallel thread so pointless putting anything in the them. Dont remove the rad cap as that will stop the fluid running out as it will create a vac lock.

    De-ionised water and antifreeze is best imo.

    110C (230F) is way to hot imo, the rad fans would be running all the time?, the stat should open up at 82-85 C and keep the fluid around that temperature.

    Tony
     
  16. TonyL

    TonyL F1 Rookie

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    Problem I have is the old veglia sender unit was defective so couldn't take any readings, the only mway I know is to re-calibrate the gauge to match the new unit. I'll let you know how I get on.
     
  17. kjw9028

    kjw9028 Karting
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    Thanks Tony, always appreciate the advice!

    Ken
     
  18. swift53

    swift53 F1 Veteran
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    #18 swift53, Jul 30, 2018
    Last edited: Jul 30, 2018
    I am not very clear, I bought a new thermostat housing a few years ago and it only has ally,
    should it have bronze sleeve as in the pic? I mean, I can go to my lathe guy and have him make a sleeve,
    but I do not understand why. Or, by the same token, it should have bronze on the large hose hole also?

    On another related topic, I really do not understand why Veglia / Jaeger, is such garbage. That goes for every Italian marque.
    Where they ever accurate?
    Possibly with the old cars, and even then, had to be rebuilt?...

    Regards, Alberto

    PS. What number and model thermostat should be used? (preferably STANT)
    All Alfas (well most) will work wonders with a Stant thermostat for a small block FORD.
     
  19. TonyL

    TonyL F1 Rookie

    Sep 27, 2007
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    Alberto.
    From my perspective the bronze liner was installed to ensure a good seal is formed on the bypass to prevent leakage through the port when closed off by the thermostat secondary disc when up to full operating temp of 82C. If it was ally, as earlier models were, then this face would / could corroded over time. In the grand scheme of things I doubt it would be a problem but some housings on the market are very poor machined quality in this area and can (do) lead to seepage past the port. For me this seating must at least be a machined face rather than a rough casting as it will lead to a proportion of coolant being circulated around the bypass port and not the radiator circuit. The pump / coolant will therefore take the easiest path and so the heat generated within the engine is not circulated and dissipated to the rad.

    I guess the liner was made that way so it could be pressed into the housing as a mod to the original design but I am guessing here.

    The gauges are not the best but given that they were made in the 60's I guess they were good at the time. The accuracy is made worse now that we can only get after market sender units. The original sender unit was a veglia unit so was matched to the gauge, I think the Maserati sender units are a matched unit but cannot get them here in the UK. For me I want to know exactly what the temperature is and it doesn't sit easy with me knowing the accuracy is made worse because of the sender unit

    I have contacted several thermostat manufacturer's and not had much luck, Stant replied and said the 13378 unit would be a suitable candidate as the pri flange is 56mm dia and will fit in the housing body with the rubber gasket, the pri disc is fine at 35mm. All good so far, what I don't know (stant wouldn't comment!) is the overall length of travel when the stat opens, will it reach the bypass port and close it off 100%. I am still investigating this. They wouldn't send me any tech details so I can work it out, which I find bizarre. Behr Thermot, Hella, Wahler, Gates and Beck are yet to contact me

    Another problem encountered is the replacement water pumps on the market. The unit I purchased doesn't have the bleed hole drilled into the casting to allow air trapped in the pump upper chamber to be vented into the upper thermostat housing. See pic of my original and you can see a small hole drilled into the pump body. All the units I have seen haven't got this and can lead to airlocking and possibly pump cavitation.


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  20. DinoParts, Stefan

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    Mar 1, 2015
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    Tony, I was following your thread after our discussion and did some more investigation myself in special as our housings don't have the bronze liner. I have two original housings we used as samples and pulled a third one out of a late E-Series last week. None of these have the bronze liner. This leads me to the opinion that the liner in your housing was pressed in afterward. Of course the liner still is a good idea to keep a good sealing surface on the long term in contrast to corroded aluminum.
     
  21. TonyL

    TonyL F1 Rookie

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    Thanks Stefan

    The housing I have is the original so not quite sure what is happening with these!

    As a side issue can you comment on the thermostats you stock for the 246. The Wahler 4033.82D seems to be a good replacement for the original fiat part as it has a much larger aperture and therefore better water flow than the others.

    Kind Regards

    Tony
     
  22. DinoParts, Stefan

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    Hi Tony,
    the thermostats in my stock are 56mm diameter. They have about 5mm more travel then necesarry to close the bypass well when hot. I did not meassure the aperture but just fixed a 246 in my workshop that was overheating. Step by step we changed water pump, thermostat, thermostat housing after your input and radiator. With every part we changed it improved and now the needle stays right in the middle, even at the 37°C or 99°F outside temperature which we had yesterday. So I consider as confirmed that the parts for the cooling system we stock work fine.

    Btw. we also had too much anti freeze in the water at first. Correcting this had a significant impact.

    Saluti,
    Stefan
     
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  23. TonyL

    TonyL F1 Rookie

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    That's good to hear these are all OK. Did you have the vent hole in the water pump?
     
  24. DinoParts, Stefan

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    The pump we took out apeared to have been overhauled lately. We replaced it because the impeller had to much space between the water pump housing on the one side and the engine cover on the other side. The vent hole was there but blocked. Our pump has the vent hole.
     
  25. TonyL

    TonyL F1 Rookie

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    I wished I had bought your one now, it would have saved me loads of lost time and frustration, most suppliers over in the UK look at me as though I am mad when I mention the problems. It is such an important piece of the cooling system to get wrong

    I had to remove the new one I purchased again (from a UK supplier) and drill the 2.5mm hole, I did put mine slighter higher so it clears the upper chamber of air. My old one was blocked as well which could be a reason why the impeller surface was badly scored / pitted through cavitation.

    I also noted the distance between the impeller was not correct either, the gap was over 4mm when the manual puts it at 0.5 - 1mm max.

    I am glad to hear your ones are much better, thanks for the feedback and hope others take note of the problems.

    Kind regards
    Tony
     

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