engine and drivetrain Radiator/Cooling system question - a dumb one.

[7502]

OK this may be a really dumb question but I ask because I've never had a car w/ a radiator before. I've driven air cooled  VW's for 35 years and always joked to my friends that I didn't trust radiators.  I have a '75 02 that the PO had recently installed a new, I think he said 320i radiator that does in fact look new. I have no coolant leaks or any specific problem that I can point to but it just seems like the engine/valve cover gets really hot and some of the coolant hoses get hot but the radiator doesn't seem to heat up as much as I expected. This morning I jacked the front of the car way up, started the car and turned on the heat and allowed the car to warm up with the intention of maybe burping the coolant of any trapped air. My coolant is clean and just over the level of the coolant fins. I didn't see any burping but I also didn't see any movement what so ever of the radiator fluid peering into filler opening. I also observed that the lower radiator hose (below the thermostat) was completely cold even after warming up the car. I measured the temperature of the coolant and it showed about 140F after 15 minutes warm up time in the garage trying to burp the coolant.  My engine temperature gauge was at about 2 oclock.

 

So do these observations seem normal? I'm concerned that maybe my thermostat is stuck closed not letting the solution circulate properly  I have a new one on order, wish I could just swap it in right now but have to wait for the package.  Of course the other thing could bad water pump, hoping it's just the thermostat or perhaps all these observations are normal?

[Simeon]

Simplistically the radiator is designed to shed heat from the water into the air so water being hot entering at the top and cold coming out the bottom is conceptually normal. 

 

What does your temperature gauge say when you are driving normally?

 

your thermostat won't be open much (correctly) at 140F, still warming up but you will get some spread of heat through convection / conduction of the static water.  The system is unusual compared to a lot of cars as the thermostat works as a diversion valve rather than a simple stop / start like other cars. It's worth pulling it to understand what temperature it is and check it's working by heating in a pan and checking it's opening through different temperatures. 

[Simeon]

Some good info in this post. 

 

 

[7502]

Thanks for that link. I knew the thermostats were dual acting in these cars and the cooling system was a little more complex, but have so little experience in this area has left me prone to overheating worries. He describes the my exact observations, although my radiator and coolant are very new and clean. I'll pull the thermostat and have a look. I guess I also have an excuse to take it for spin and see if I can heat it up enough to open that lower thermostat valve.  It's just been bugging me how every time I check that lower hose it's completely cold but the thermostat and everything above seems pretty hot.  Who knows it may be behaving exactly as intended.

Edited September 28, 2016 by 7502

[Simeon]

There are usually a few things you can see together in my experience. Cars with new radiators have often had issues with overheating. Before splashing the cash on a radiator people may try installing a lower heat thermostat or even butchering the innards to remove the plates. This isn't the same as doing this on a conventional stat so check that the plates are all in there and working. 

[TobyB]

Quote

My engine temperature gauge was at about 2 oclock.

 

You mean, above horizontal?  Most of us like to see horizontal, or a little below.

 

BUT that gauge is notorious for being wrong, so I tend to put a real gauge on, first thing.

 

Yes, you want a cold lower rad hose.  Means you have a good radiator.

Water pumps very seldom fail, but if yours did, that would give you low flow.

Thermostats can be boiled in a pan on the stove.  You get to watch it work.

Stick a candy thermometer in the water and stir, and you can see when it opens.

and maybe more importantly, watch HOW it opens- which should be smoothly. 

If it suddenly jumps, either opening or closing, it's time for the float test.

And if it's not fully open by the time the water boils, same thing.

 

hth

 

t

 

[7502]

Thanks Toby, I took a nice drive this morning freeway, country roads, ending w/ city driving and the lower radiator hose was cold again. My heat works very well so I guess my pump is doing it's job.  My thermostat always ends up around 2:00 to 2:30 o'clock, so above horizontal.  I'll remove my old thermostat and test it when the replacement arrives. Here's a shot of the radiator it's marked Behr. Is this a common replacement style?

[KFunk]

55 minutes ago, 7502 said:

Thanks Toby, I took a nice drive this morning freeway, country roads, ending w/ city driving and the lower radiator hose was cold again. My heat works very well so I guess my pump is doing it's job.  My thermostat always ends up around 2:00 to 2:30 o'clock, so above horizontal.  I'll remove my old thermostat and test it when the replacement arrives. Here's a shot of the radiator it's marked Behr. Is this a common replacement style?

 

Just an FYI, that E21 / 320i radiator is a common swap.  Some people don't like the plastic top ones, but it should work well and be a bit of an upgrade over the stock one.  It does mount differently.  Notice that the ears at the top aren't used, and instead holes are drilled on the sides.  The tabs holding the bolts on the rad are actually meant for the E21 fan shroud, so a little flimsy, but it works for me and many others.  Also the lower hose exit point is different, so you may see a bit of a hack job there to get a hose to fit it (make sure its not pinched).  

Edited September 28, 2016 by KFunk

[Mike Self]

Your thermostat should be marked on the outside with its opening temperature--in Celsius.  I normally run an 80 degree 'stat, and in warm weather my temp gauge generally runs just above the horizontal--between 2:30 and 2:45.  It also means quicker warmup and more heat more quickly in cold weather (no, not in snow!).  

 

If you do remove your thermostat to test it in a pan of water on the stove, suspend the 'stat on a piece of string so it doesn't touch the pan.  If it touches, the pan will conduct heat to the thermostat body and affect its opening temperature.  

 

cheers

mike

[jimk]

3 hours ago, 7502 said:

I'll remove my old thermostat and test it when the replacement arrives

Test the new one before you take things apart.  Make sure it is ok.  Plus you get all that experience of testing.  With that knowledge, it will be easier to convince yourself that the old one is good or not.

[jgerock]

I come from the air cooled crowd too.  When you said "burp", did you have the radiator cap off and squeeze the large hoses (not hot but warm)?  Engine off at first so you can see any bubbles in the top of the radiator.

 

 The temperature gauge should not jump around when you turn the lights on or use the blinker. If it (or the fuel gauge) does, then you should add a separate ground wire to the rear of the gauge cluster.

 

Neat Ghia in your picture...

[7502]

What i meant by burp, or attempted burp since in my case it failed to burp, is to raise the front of the car about 18 inches and run the engine w/ radiator cap off.  I made sure my heater valve was open and turned the heat on high. As it was warming, I tried squeezing the hoses and looked for bubbles or anything else exciting through the radiator cap opening. I did this for about 15-20 minutes but saw nothing, so air in the system doesn't seem to be an issue.
My temp gauge doesn't bounce around, it always moves real gradual.

 

I will look for the temperature rating on the old one and test both side by side. I can't remember the rating of the one on order. I like to clear things like this up and then put them out of my mind. 

[PaulTWinterton]

To add to your knowledge base: you can get modern cores for the radiator.  Some people go for the 3-core (3 stacked channels) or more cores per inch, which means more channels from side to side.  Both these options mean more coolant (up to 25%) to cool your engine.

 

I opted for using my original rad with more cores per inch.  For 2 years my gauge has stayed at the 3:30 position, even idling at the US/Canada border crossing for an hour at the height of summer.  The only time it rises significantly is after a spirited run and turning off the engine abruptly.   Start up would show the temperature at the 2:00 position and then drop back to 3:30.

 

I spent years watching my gauge climb and drop through different weather, and driving situations.  It's a joy not to worry about overheating because of marginal coolant flow.

 

One other thing that is commonly ignored is the drain plug in the block under #3 exhaust port.  Draining your block to ensure there is no sludge is a good practice.  If you do have sludge in the block it can hinder the flow of coolant.

 

For me a basic rule is: if your heater blows hot air, you have good coolant flow.