355 M5.2 coolant temp

Is it normal for the 355 M5.2 to have the coolant temperature to always be changing depending on the outer temperature and the air flow to the radiators? on a +17C(63F) on the pic. it is about 140F (+60C) and on a hot day with a +28C (82F) it's going between 185F (+85C) while on the move to 220F (104F) on a traffic light standing still?

Both L and R fans are working on/off when standing still.

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Hey long time no see!

Is your pup having always the same water temp or it varies during the ride?

 

In my case it was low coolant. The matter is there always will be coolant like 1cm/ 1/2" from the bottom so I thought it's a thermostat. When I replaced it and added in about same amount of coolant that I lost everything was exactly the same. Then I replaced the fans switch in the left radiator and when unscrewing it I learned on the top of the radiator there was no coolant coming out but air. So I replaced the switch (1 change at a time) and learned the coolant temp improved a little on the gauge but not much. So my original fans switch was made on 41 week of 1998 so for 26 years of service its sensivity must be degraded but only very little. So I started reading the WSM vol 1 and it says in there coolant needs to be not less than a 6cm from the top of the expansion tank. And I had like 8mm from the bottom which is like 8.5cm from the top. Adding cooland solved the problem. FYI: The WSM saying to add coolant on a working engine with setting the heater to the highest temp and you need to balance b/w coolant expanding when it warms up and not to overspill the expansion tank and yet the cooland will circle in the engine until the temp rises to 180C (82F) only then the thermostat starts opening up letting the coolant to the radiators so I was adding it little by little until a half-tank then stopped engine put a cap on and added more overnight to those 6cm from the top of the cap - I used a clear plastic straw with a marks I put with a black marker on it.

The discrepancy is the WSM vol. 1 says: coolant MIN is 6cm from the top while the 355 Owner's Manual says: the coolant MIN is 6-8cm from the top.

 

In my case it was low on coolant.

 

I had replaced the thermostat to the 355 M5.2 part number (yellow copper thermostat) - I had a silver thermostat for 355 M2.7 which is the same just a diff. manufacturer and re-added same amount of coolant and the behavior was exactly the same. Then I replaced the fans switch in the left radiator and when unscrewing the original switch I learned it was air in the top of the radiator and no coolant was coming out. So I replaced the fans switch (1 change at a time) and learned it as a very little improvement but very cosmetic meaning the original fans switch which was built on week 41 of 1998 lost some sensitivity to the temp on closing/opening but very-very little. The matter is there was about a little coolant on the bottom of the expansion tank so I thought it's either the thermostat or then the fans switch. So I looked into WSM vol 1 and it says the expansion tank should have a minimum 6cm of coolant from the top which is about 3.5 cm from the bottom and I had 8mm. Adding the coolant resolved the issue. And per WSM the coolant needs to be added when the engine is warming up (so the thermostat opens @180F letting the coolant to the fans (and with the heater set to the max). Then I let the car cool overnight and added the coolant to a cold car.

The matter is the WSM says the min coolant is 6cm from the top and the 355 Owners Manual: 6-8cm from the top.

 

Sorry I didn't get your comment. What I was trying to say because it was some coolant on the bottom of the expansion tank I initially thought wasn't too little of it since the tank is not having any min/max marks nor any built-in measuring sticks.

 

The expansion tank has 4 pipes: 2 on the bottom 2 drain on the top. The thicker hose #28 on the bottom on the left is going to the pump. The less thicker on the right hose #18 is a return from the heater. Left drain hose #7 takes air from radiators return and the right drain hose #3 takes air from the water pump. So. the hose #18 is connected to the nipple which has some ditch cylinder on the bottom of the expansion tank so it always will get the coolant regardless of the coolant level of 6 or 8cm below the filler cap edge.

Now, the hose #18 which is a return from the heater as I observed is the key. the intake pipe in the tank seems is higher that the bottom of the tank. I think it is right below the 8cm from the top mark thus you need never to be below that 8cm mark.

Air pressure. The cap for 355 (Part 145030) is a 1.00Bar cap, it's not some are 0.9 and some 1.1. It's all the same for 355 (and for many other models) so the matter is all liquids expand and shrink when the outside temp is higher or lower on a cold car. So, the Owner's Manual is right, but they needed to say the 6cm below the filler cap edge on when it's warm and 8cm when it's cold. In the WSM they just simplified it saying 6cm.

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One more thing. The WSM says to bleed the system when filling it up, but the bleeding screw #29 is just below the steering pump expansion tank and with the coolant expansion tank in-place (or even hung but with the hoses connected back up there is no way to move anywhere out the way the steering pump expansion tank and its' 2 hoses will be in the way even to reach to the coolant bleeding valve. The thermostat cap/pipe #28 is a carry-over from Mondial-T so I think it was bled with the screw on that one (and the self-bleeding became popular in the late 90-s on so in the Mondial T which is MY88-93 it was no such a thing as self-bleeding. The same pipe with the bleeding screw also is used for the 348, the 348 diagrams showing the cooling is very similar to 355 but the pictures of the engine in the engine compartment not showing clearly if the 348 bleeding valve is reachable when everything is in-place or not?

Anyhow, as in the 355 the bleeding valve is not reachable I was tending to believe the 355 cooling is a self-bleeding thus after adding the coolant on the warming-up engine as stated in WSM, I drove the car next day (with the over-night cooling) with the heater to the maximum to ensure all air is out from the system.


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Why don't you to take your smart comments elsewhere?

 

pump feed pipe (?) - Yes.

No as it's unfolded in my case, it's not. To see of where the nipple inside the tank for the heater return intake is you need to rip off the tank or use a tiny videocam they use to see inside the engine cylinders over a spark plug hole. But as I had stated, had like ~8mm from the bottom (maybe 7mm) and thought it's OK and learned when replacing the fans switch the left radiator had air in it.