temperature gauge

[deQuincey]

hello I own a 1971, BMW 3,0 CS

the carburetors version, mounting 2 zeniths

I am worried because I think that the temperature of the cooling liquid is excessive, in this photo you see the normal position of my temperature gauge while driving in 4th gear at 80km/h in a flat road with outside temperature of 12 ºC

when I stop the car the gauge goes up even, but not entering the red zone never

I made an important restoration of the cooling system one month ago:

- clean the circuit
- new tubes
- new water pump
- new radiator
- new fan and visco clutch
- new bosch sparks
- new thermostat
- new temperature sensor
- new cooling liquid, complete bleeding of the system

there is also a fact that is: when the engine is hot, if I stop the car, and few minutes later I start it again, the temperature goes down until the gauge is below the middle of the scale for a few seconds
(I may think that this means a sudden and big opening of the thermostat), the question is why this is not happening normally

do you think this level of temperature is normal running condition ?

regards and thank you for helping

 

[pmansson]

I agree about checking with a thermometer. One of those "laser" guns aimed at the hoses and thermostat housing.
Unless you spend time in rush hour Miami traffic, you might try the European 80 degree thermostat (instead of the US 72? degree unit).

 

[tochi]

Unless you spend time in rush hour Miami traffic, you might try the European 80 degree thermostat (instead of the US 72? degree unit).

Last time I visited Miami, there were three types of driving: Slow, stop and slow, and fleeing (which usually involves driving in the oncoming traffic lane!) :lol:

Depending upon the sensitivity of your fan clutch, a slight rise in temperature can be normal if you are idling and the fan is a little slow to engage. I experience temperature fluctuations similar to yours if the engine idles long enough. Its worse if air conditioning is used. With the hood open, as soon as the fan clutch engages, you feel the rush of air it produces and my gauge immediately descends from 2:30 o'clock to 3:30 o'clock. It rarely sits at 3:00, which I attribute to a specific gauge peculiarity. With a different fan clutch or on the hottest of days, the clutch engages earlier. This gauge fluctuation at idle or when sitting in traffic, is often more noticeable with electric fans.

A thermometer including the laser guided type mentioned by PMansson should give you peace of mind.

BTW: I haven't changed by thermostat for years but if memory serves me it is a Whaler or Behr unit rated at 75 degrees C.

 

[deQuincey]

thank you both for your kind answers

let me explain better the problem, because yes, it can be a fault in those parts, but,...

some additional information:

when I start the engine, both big rubber tubes that go to and back from the radiator are cold, and also you can compress them with your hand (they are not hard)

little by little the engine warms up, you can feel that the upper tube that goes to the radiator warms up, and the gauge starts moving up also, but the lower tube of the radiator (the one that comes from radiator to thermostat), remains cold

you will be progressively gaining temperature in the upper tube, and the gauge, but the lower tube remains cold, similar thing happens to the radiator, the left upper side becomes hot, the rest is cold

the fan is rotating, but the visco is not becoming blocked (because little radiation is comming from the radiator), so the fan is not performing in it´s maximum

the gauge stops five millimeters before the red area and is maintained there

another point is that the upper tube by then, has become really hard (difficult to compress with your hand)

that upper tube is very very hot, you can not stand with your hand touching it (i will borrow a laser thermometer tomorrow to meassure that value)

conclusions by now:

the thermostat is not working well, I can not understand this, the thermostat is new, a 80ºC one, it has been bleeded, and a tiny hole of 1/16" (1,5mm) has been done to improve air bubbles passing through to improve bleeding

possible problem:

a mechanic contacted by phone has told me that the problem seems to be one of air leak, more specific, air passing from the engine combustion chambers to the cooling system through the gasket, or a crack, in his opinion this explains the hard upper tube and the high temperature (yes this is not explaining why the radiator is not having running water inside)

this would be a serious problem, but how can I check it before opening the engine ?

please advise

another last corollarium: now with everything hot, if I stop the engine for one minute but maintaining the contact to have the gauge alive, I will see that the gauge goes up a bit and stops there again before the red area, and NOW if I restart the engine, suddenly the gauge goes really down (lower than the middle) for one or two minutes, and then up again, as if the thermostat and radiator had been working for those two minutes only


regards

 

[MMercury]

the thermostat is not working well, I can not understand this, the thermostat is new, a 80ºC one, it has been bleeded, and a tiny hole of 1/16" (1,5mm) has been done to improve air bubbles passing through to improve bleeding

a mechanic contacted by phone has told me that the problem seems to be one of air leak, more specific, air passing from the engine combustion chambers to the cooling system through the gasket, or a crack, in his opinion this explains the hard upper tube and the high temperature (yes this is not explaining why the radiator is not having running water inside)

this would be a serious problem, but how can I check it before opening the engine ?

Unfortunately, parts do not have to be old to fail. :wink: Your temperature observations of the upper and lower radiator hoses warrant removal of the thermostat and either replacement or testing. (Testing = put it in a pan of water on the stove, heat and serve using a thermometer to determine when, or if, it is opening) See "testing" described below.

I am not sure I follow your mechanic's logic. If you have a cracked or compromised coolant passage in your cylinder head, or bad head gasket, gas that is forced into the cooling system should displace the coolant. In fact, this should over-pressurize the system so that you see coolant forced out the overflow tube or see bubbles in the overflow vessel. A compromised head gasket can also allow coolant to be sucked into the cylinders. You would likely see vapor out of the tailpipe and again lose coolant in the process. You might also see evidence of moisture on the spark plugs, and in some cases, the coolant will show up in the oil looking like a batido (milkshake).

Check on your thermostat before worrying about the bigger things. See "testing" below:

 

[Arde]

After seeing your great tutorial on the cooling system rebuild who am I to say anything useful? Just a couple of items from cooling system experiences on E24 and E36 models.

1) Your high temp indication occurs at 80km/h, at that speed in March in Bilbao the fan is not needed for the radiator to be effective, so I would exonerate the fan. I would also exonerate the radiator almost.

2) There is no mention of the heat exchanger in your post. I recall the heater controls should be open when you bleed the system. If the cabin fan cannot blow hot air into the cabin you can deduce that coolant is not circulating effectively through the heat exchanger.

 

[deQuincey]

I would like to thank you very much for your answers, through them some points are arising and hopefuly one of them will be the key to solve the problem

yes I have to check the thermostat, I need a termometer for that (enough to reach 100ºC), and I don´t have it at the moment, I will do in the next days

mr. mmercury, I coincide with some of your ideas about the erroneus diagnosis of my mechanic, some of that points are needed to happen to assess the engine problem, and by now they aren´t

mr. arde (what a nice name for a place: "cupertino", I assume that the pronuntiation in english will be music for the ears), I agree that there might be a fault in bleeding due to the heating system, that system is not working well, (i has not worked well for years), because no warm air is produced.

when I cleaned and refilled the cooling system the heat controls were open, but I don´t know to which extent that meant that the coolant was passing through (many thinghs could be trapped or misfunctioning there to reach that wrong performance, and I can not tell by now)

so, yes, I will have to pay some attention to that

this weekend I intend to perform some temperature checks, to have some nummerical data that may put a little light in this

thank you again

farewell

 

[deQuincey]

dear all

solution has came to me thanks to those disconected ideas from here and there, I want to thank you for those ideas and advises

reason for the problem: air bubbles, so incorrect bleeding, but...

how is this possible if you consider that I have been bleeding the circuit through the apropriate screw up to a dozen of times ?

the answer is: the bubbles formed inside the circuit do not move evenly towards the "exit" sign as if they were schoolboys, so you have to help them in the way out through the "other" egress mean,...eh ?...what ?

yes, say it aloud, you´ve got it ! the expansion vessel !!

but how can you do that ?, it is possible and easy, but you need a new cap, because the old one has to be tortured !

you have to drill a small hole (I did 3mm hole) in the lower part of the cap near it´s center, this hole will allow air bubbles + some coolant pass to the cilindric chamber formed by the neck of the vessel and the cap itself, in that reservoir you have the opening hole that allows excessive presure go out through a tiny tube

pepared this apparatus you start the engine and carefully pay attention to warming up of engine, tubes, radiator,...take a look on the gauge !, and so on

after a while you will see that the liquid + bubbles are starting their way out through the tiny tube, don´t worry, but look again and again to the gauge, check tubes,...

you should accelerate to force the coolant move quickly and this way take the bubbles from inside the engine to the vessel

check the coolant level, the vessel should be full anytime, you will drop away some, don´t worry, if there is enough in the vessel no harm will be produced, and you are not going to spill so much liquid in this process

after some minutes you can assume that the bubbles are away, and then, you can take off the drilled cap, and replace it by the new one, and that´s it !

you liked it ?

it works !!!!!!!!!!!

best regards and vielen danke !

stay safe

 

[Arde]

Cupertino is celebrating the solution of the puzzle. There is wine branded Cupertino (from Italy I think) but don't have one handy to celebrate with you.

Pesky and invisible air bubbles? There is an idea for Orangener who promotes the transparent turn light lenses. How about transparent coolant hoses so you can see air bubbles in the system?

 

[bill]

Looks like DeQuincey has hit on the problem of incorrect bleeding of the cooling system (see Volume 3 of the dearly departed CS Registry newsletter) . Our beloved coupes are not GenMoFordSlers and so require a few more steps before the bleeding is effective. Getting coolant out of the bleed screw is not enough to bleed the system. The main problem I have found is that coolant does not completely fill the hose between the thermo and radiator bottom. This can prevent coolant circulation. So whenever I drain the system, I disconnect said hose at the top and fill it up as much as possible before re-connecting. Then the engine is run for 20 mins. or so, revving it every so often while keeping an eye on the gauge so as to be sure it does not go above 3 o'clock, and squeezing/checking for heat all the hoses I can reach. Then shut off the engine, let it cool down to the blue zone, check coolant level and top up if needed. Run the engine again as before, and generally after that it is OK. Another labor of love!

 

[MMercury]

Looks like DeQuincey has hit on the problem of incorrect bleeding of the cooling system (see Volume 3 of the dearly departed CS Registry newsletter) .

There are apparently several ways to purge the cooling system of air. With no particular favorite, Here is another, courtesy of E28 board and J.Rowe at Metric Mechanic:

"There is a sure way to bleed the cooling system on 'big' six engines.
1. After repair is made (before adding coolant) remove bleeder screw and run a small piece of wire down the hole to dislodge any mineral deposits..
2. Replace the screw, but leave valve 'open'.
3. Open heater control valve and add coolant until it begins to escape from the bleeder hole.
4. Now close bleeder screw and replace the expansion tank cap and tighten.
5. Remove the small coolant line that runs from the radiator to the
expansion tank AT THE EXPANSION tank and hold it as high as you can.
6. Now attach another hose the expansion tank in place of the one you've
just removed. BLOW (gently!!) through this hose until coolant emerges from the small elevated radiator hose.
7. Now remove the 'blow' hose and reconnect the small radiator hose to the expansion tank..
8. Now top off the expansion tank to the full mark.
9. Start and warm up engine and check for leaks!!"

 

[deQuincey]

hello

thanks for that interesting trick

I will check it anyway

regards

 

[DaSurfa]

Sorry to bring up this old thread but my 71 2800 is doing the same exact thing as deQuincey's car after I redid my whole cooling system.

The only difference is that I took out the stock mechanical fan and only put a 16" flex-a-lite electric fan in front of the a/c radiator as the only cooling fan. I ordered the wrong water pump with the flat top and the old stock water pump had a bolt on top and thats why I never installed the old stock screw on fan.

Hopefully the trick with overflow will fix my problem. If not, I gotta find a new fan and fan clutch that will fit onto my flat top water pump. Anyone know what the exact part number for these?

Thanks,
David

 

[deQuincey]

Sorry to bring up this old thread but my 71 2800 is doing the same exact thing as deQuincey's car after I redid my whole cooling system.

The only difference is that I took out the stock mechanical fan and only put a 16" flex-a-lite electric fan in front of the a/c radiator as the only cooling fan. I ordered the wrong water pump with the flat top and the old stock water pump had a bolt on top and thats why I never installed the old stock screw on fan.

Hopefully the trick with overflow will fix my problem. If not, I gotta find a new fan and fan clutch that will fit onto my flat top water pump. Anyone know what the exact part number for these?

Thanks,
David

i would suggest walloth&nesch
regards

 

[echappe]

I have found that it helps to have car on an incline with the nose high when bleeding