Radiator and overflow cap pressures

This is 0.7 or 0.9 bars depending on cars. For my 400 GTA is 0.7.
I opened a subject following an overflow problem here :

http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/326049-explosion-coolant-running-highway.html

 

My caps were initially in wrong place but a posting a few years ago corrected that. The pressure cap goes on the expansion tank! A no pressure cap goes on the radiator fill neck. Seems backwards but that means your expansion tank is pressured. Expansion tank is really the wrong name for it; better name is vent tank. The expansion is all supposed to take place in the upper tank of the radiator and if filled per the manual that is what happens. The vent tank should be empty and stay empty hot or cold. If engine overheats the steam will condense in the tank since it is pressurized too.
Ken

 

Ok, so I have been having sporadic, slightly elevated coolant temps lately. A local mechanic suggested I check the expansion tank pressure cap so I did. I did this completely cold and there was a lot of pressure in the tank and the cap broke into three pieces. So I need another one. I looked at Table 18 - Cooling System and it doesn't show a part number for just the pressure cap.

Anyone have a part number/replacement for just the cap, or a spare one for sale?

Also, is a .9 bar or a 1.1 bar? The one I had was 1.1 but other threads seem to suggest .9 is correct.

 

System has two caps and I had them backwards for first couple of years and switched them with no plus or minus differences. The one on the radiator has no pressure or vacuum setting; it is a "flow thru cap" to keep fluid sloshing out. The opne on the tank is 0.9 bar or 12 or 12.5 psig is a typical cap. Both caps are NORMAL everyday old school caps you can get at NAPA (you can add the gold plating yourself).

Looks like I just repeated a previous post more or less.

Now, pressure when cold....???
Ken

 

That does seem strange to me, but it definitely had pressure and it was completely cold. Is this normal?

 

Are you filling correctly? The top of the radiator is the expansion tank not the auxiliary tank! You must only fill (cold) to 15 or 18 mm below the filler spout. If you fill the radiator that could give you pressure when cold.
Ken

 

Thank you for the suggestion. I have never personally added coolant, but if I had it would have been into the radiator. I will check the level tomorrow when I fit the new cap. I wonder if the cap was faulty and never released any pressure?

 

I need the forum's help. I noticed a couple of weeks ago my coolant temp. creeping up above what is normal (just below 90c) for my car. It does run a little warm while going down the road, but really heats up at idle - up to 100c. I shut it off at that point.
I checked the coolant and level. It is green with nothing else in it, and it is below the filler neck as suggested.
I also checked the operation of the fans and they all come on when the temp. rises just as they always have.
I used my temperature gun on the radiator and had a reading of 228F at the top of the radiator near the thermostat, and around 180F at the lower passenger side bottom of the radiator.
Does anyone have any suggestions as to what I should do or what the problem is?

 

The items listed in this topic you will resolve your problem .
The methodology was determined by a specialist of this engine. If you respect it you find disorder your problem . First verify that your calorstat is not useless. Good research...

http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/326049-explosion-coolant-running-highway.html

 

Thanks for the response and I had read that thread prior to posting my question. Any further help would be appreciated.

 

It seemed backwards to me too & the half of me wanted to change it to the conventional way you see in practically every new car now. I still don't understand Ferrari's/Colombo's engineering with this
I still think that you could fill the radiator full with coolant, put the pressure cap on it, & use the expansion tank to capture the coolant as it expands...& install the non-pressure cap on the expansion tank. I'm reluctant to use the car as a ginnypig on this!

Back in the day of no expansion/overflow tank, the coolant level was supposed to be 1" below the filler neck, capped with a pressure cap. That 1" of air was there to absorb the expansion of the coolant (in the form of pressure).
Then along came the expansion/overflow tank. While the radiator remained capped with a pressure cap, the radiator was to be completely filled with coolant. Plus, the expansion tank also contained a small amount of coolant brought to the 'low' mark on the tank (the static condition when the engine is cold). The expansion tank never sees pressure, it only accepts coolant when the engine is heating up & allows coolant to return back to the radiator as the engine cools down. The cap on the overflow cap is generally a plastic one that has an overflow hose attached to it that vents all the time.

As for the 365/400/412 however, there's supposed to be a 1/2" or so of air in the radiator that is capped with a non-pressure cap, plus the air in the overflow tank that absorbs the expansion of the coolant. I've noticed after the engine heats up & thermostat opens, all kinds of coolant comes gushing back into the radiator (observed with the radiator capped off) & I have no doubt that some coolant will find its way through the overflow tube & into the expansion tank. The tube in the expansion tank is a dip style tube, meaning that it goes to the bottom of the expansion tank. As the engine cools down, the escaped coolant will be sucked back into the radiator...thus leaving the tank 'dry' (if all is working properly!).

With your readings of 225 @ top & 180 @ bottom of the radiator, it appears your radiator & fans are in working order...and I'm assuming you're not hanging over the front end of the car @ 60 mph to get these readings but when it's parked
I'm wondering if your thermostat is partially opening, with some of the hot water from the engine bypassing the radiator

 

My car had the pressure cap on the radiator & the non-pressure one on the overflow when I got it. One thing I did notice with this setup was that after the engine is turned off & the heat soak from the engine expands the coolant a bit further you get a lot of gurgling in the overflow tank. Modern cars running this setup tend to have the overflow tank mounted higher than the radiator with the hose entering the overflow tank at the bottom to prevent this gurgling. When I reverted my car back to the setup in the manual I no longer get this gurgling noise after I switch the engine off - nice & quiet.

Cheers Al

 

Thanks for the suggestion. Mine are on correctly, with a new Stant 1.1bar cap on the expansion tank.
I just can't figure out why it runs hot at idle only. All the fans operate correctly, there are no real cold spots on the radiator, and it just started occurring. There are no leaks that I can find - no drips, no sprayed coolant underneath, no loss of coolant as the level remains the same, nothing.
I ordered a new thermostat, but I don't see how that could be the cause of the problem.

Are there any tricks to changing the thermostat?

 

Good day Darren,

It is possible that the thermostat is not opening at the right temperature (or perhaps closing when it should not), but also that it is not fully open ... thus restricting coolant flow.

I would also look towards the radiator as well. Although you indicated that you are indeed seeing a temperature differential through the radiator, it may have some plugged, etc passages which would also restrict coolant flow.

Cheers,

Sam

 

It is possible to dismantle the thermostat to test it, removing the hull as the picture 1 . Extract the thermostat as in picture 2. It heats water in a vessel is immersed in thermometer and checked it closes and opens normally. in this case it all goes . The mark of thermostat BEHR No. 2005 . It equipped many civilians and military vehicles around 1970 . The thermostat tripping temperature is 79 ° Celsius .
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Thank you both for your responses. I hope that it is the thermostat. I have one on order that includes the entire housing, but I now question whether I needed the whole thing seeing one taken apart. Can just the thermostat itself be purchased, and if so, where?

 

I looked the only thermostat for several months without finding one that fit . Purchasing the Full Body is needed. However I paid my own about $ 30 on Ebay while in Superformance it must be worth more than $ 250 .

If the used thermostat fulfills its function simply put it back in the box using joint compound for sealing .

Good research

 

Superformance did in fact have the part (#106393) at the most "reasonable" price - $287.00US. Others had the exact same part for over $500US.

Just a quick question about installation. How hard/easy is removal/replacement of this part? Is there any need to drain the coolant prior to installation?

 

Look Here :
NOS Mercedes Ponton Behr Thermostat 79 C 2 014 79 W120 W121 180B 190B | eBay
The position of the lower hose is not exactly the same but it fits.
The price difference is well worth the adaptation.
For installation simply remove the hoses after emptying the upper part of the radiator.
I know this is not exactly consistent with the spirit of the restoration original state but it can be an alternative waiting to find a "normal" price .
The practice craves a high price under the pretext that it is a replacement part for Ferrari
exasperates me . This spare part is of German origin and equipped many vehicles . Just wait to find the exact reference. I found mine on eBay , brand new for $ 30.

 

Doh! I just bought one of these in a yellow box for way too much.

 

Anothers : Thermostat, Kühlmittel BEHR HELLA SERVICE TH 20 79 | eBay
Thermostat, Kühlmittel BEHR HELLA SERVICE TH 17 79 | eBay

 

More :

Thermostat, Kühlmittel TH 20 79 von BEHR HELLA SERVICE | PartsRunner
80.06401.6001,MAN 80064016001 Coolant Thermostat

 

Are any of these a direct replacement, or would they require some modification?

 

No change, the hoses of our car are in 45mm.