Cooling update and a couple of questions

[The Warden]

Hello!

Greg, before you yell at me again I successfully completed half of the trip; I'm currently in the L.A. area (actually at my grandmother's at the moment; I'm going back to my dad's on Tuesday and coming home on the 4th.

So far, things have been pretty good overall. I've got a weird creaking in my front end that I'm going to start another post about; other than that, I believe the car's happy. I was able to go over the Grapevine twice without the car overheating.

I do have a couple of questions, though.

First, I'm noticing that the car's running warmer than it had in the past. Before the old thermostat went bad, the gauge would get to just a hair above 80°C and stay there, except on warm days where it would get up into the 90° range. With the new thermostat, it's getting up to a little bit above 90° before the lower radiator hose starts getting hot. In addition, the gauge seems to be moving quite a bit more; mainly slowly fluctuating between 85° and 95°. My first thought is that the thermostat's opening up later than expected ("80°" is cast on a flange on the new thermostat), but without pulling it and checking it (that'll wait 'till I get home), I can't be sure. Also, I remember hearing that the thermostat's supposed to start opening at a temperature and should be completely open by a different temperature, so mayube this is normal? BTW, if it makes a difference, I'm running a roughly 50/50 mixture of distilled water and Zerex G-05, with one bottle of Water Wetter.

Also, how long should it take for the cooling system to be completely purged of trapped air? I filled the system through the upper radiator hose and the expansion tank (which should have filled the radiator), and I'm assuming that there will be air trapped in the system that needs to work its way to the expansion tank. It's been about 300 miles since the last flush, and in that time I've checked the expansion tank level (I really wish that there was a cap on the radiator itself) 5 or 6 times and have had to add coolant each time (maybe 3 cups worth; that's just an EWAG).

Sorry to bug everyone again on this again I know people are getting sick of me yappin' about the cooling system on my car, but I'm hoping that this'll be over pretty quick (unless I have an undetected leak, I can see the light at the end of the tunnel).

Any comments would be appreciated...thanks in advance!

[leathermang]

The thermostat has two holes to control flow through.. and springs that are calibrated to open at different temperatures for each....
I think you are in good shape and should try just enjoying your holidays....
I have been getting in trouble lately giving 123 chassis info out of my manuals to non 123 people...
Just keep watching that expansion tank and try checking it at the same temp ..... either cold or hot.... so you don't overfill it ....
So are you running a fan clutch or not ?
Are you running an engine fan at all ?
I don't remember what you decided for this trip....

[Ken300D]

I'm a few days behind you with a thermostat change in the 300SD. After the first run (hot-cold) cycle, I lost just about the whole reservoir to (apparently) replace air. But I only filled the system through the reservoir.

I'm getting fluctuations too as the engine heats up, but after about 30 minutes run time it settles down to a nice steady 90C or so indication. I'm fully satisfied with that.

And, I expect the fluctuations to generally go away once all the air gets purged from the system. At this point I'm not sure how many more hot/cold cycles that will need.

I'm running 50/50 Mercedes coolant. Although the head is iron, the thermostat housing looks to be aluminum, and you don't want those to corrode because that's where the cooling system "bypass" gets sealed off by the thermostat flange. So far I have no corrosion there.

Have a great trip and enjoy a heated car.

Ken300D

[samiam4]

Seems strange,

Are you using a mercedes or aftermarket thermostat? My car acts up when the radiator didn't hold pressure. Are you leaking any fluid over time??
Mine with the leak fixed is rock steady 86 C. It's factory part.


Michael

[psfred]

You need to burp it, you still have air in there.

I think you can use the system for the M103 and OM603 -- get a pair of pliers or channelocks, whatever will squeeze the hose from the rad to the tank shut.

Squish the upper radiator hose flat (with cap off tank), then holding it flat with one hand, squeeze the small hose to the tank shut and release the upper radiator hose. Usually get some gurgles the first couple times with a significant drop in level and you suck the coolant out the bottom of the reservior. Repeat until the upper tank hose delivers only coolant. Keep tank full.

Your temps should steady up then.

Run engine with the heater on full blast, then repeat -- this will purge the heater core too.

Getting these things full of coolant takes some time and effort, you cannot just fill them up and be done with it.

Peter

[The Warden]

Originally posted by psfred
Getting these things full of coolant takes some time and effort, you cannot just fill them up and be done with it.

I had a feeling that that was the case. Peter, thanks for the explanation on the procedure on how to get the air out; I wish that I had had this earlier. Maybe it'll work with a Ford too (the 6.9l IDI is also prone to getting air trapped in cooling passages following a flush).

Just want to double-check; when you talk about the hose going to the expansion tank, are you talking about the tiny hose that goes to the top of the radiator, or the larger one that goes to the bottom? I presume that squeezing the upper radiator hose with my hand will be sufficient for that end.

Thanks again

[psfred]

Yes, the tiny hose at the top of the rad.

You would think that the system would simply gravity fill with the air venting out that small hose to the expansion tank, but it doesn't. You have to help it. Otherwise the radiator stays half full of air, and you get funky cooling -- hence the oscillating temp gauge.

I nearly fried the TE after putting a water pump on -- engine temp shot way up and all the coolant in the tank vanished, but when I added more, even with the engine hot, it just sat there until I remembered the trick -- got it full in next to no time, no trouble since.

Peter