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  #1  
Old 03-05-2004, 11:37 AM
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Question 300CD: endless appetite for anti freeze?

Here's a wierd one:

I keep adding anti freeze to the overflow tank, about half a jug twice last month. I do this when I notice that the temp guage goes WAY up but I still have no heat in the car after about ten minutes of morning driving. After I stop and add the anti freeze, things go back to normal for about a week or two.

This has been going on for the last month, after I had the block heater replaced, then did the thermostat myself.

There is zero leakage anywhere, and I don't ever see any white or other smoke coming out the back.

Engine is warm after driving (I only go a few miles to school) , but the radiator is stone cold to the touch.

Water pump and radiator are less than two years old.

Mono valve looked fine when I checked it two summers ago (I took it apart and inspected the diaphragm)

Recently replaced the CCU, since the fan speed was all over the place; this didn't help very much, but I also hear a slight whining inside the car whenever I turn on the heat. Sounds like vaccum escaping somewhere. Not sure if this relates to the anti freeze situation.

SO: Where the hell is all that anti freeze going, and why does it sadistically pick the coldest mornings of the year to decide to stop working?

Why don't I ever get the easy stuff like flat tires any more?
Waaaahhhh!

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Old 03-05-2004, 12:29 PM
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HEAD GASKET

ITS YOUR HEAD GASKET
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Old 03-05-2004, 12:35 PM
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Question Head Gasket?

If it's the head gasket, then where the hell is the white smoke, anti freeze smell, etc?

Wouldn't the head gasket be accompanied by sigificant loss of power also? Not that this is noticable in a diesel...
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Old 03-05-2004, 12:58 PM
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not necessarily in the small doeses you talking about. you could go to a parts store and get a leak dection kit for not too much money and the be sure where it goes.
sorry i am not more help
JOHN M
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  #5  
Old 03-05-2004, 02:13 PM
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Replace your radiator cap and make sure the thermostat actually works -- I assume you put it in right side up (flap and capsule toward the engine).

If the thermostat is bad (they sometime are, right out of the box)and not opening, in combination with a bad cap, you are boiling the coolant out while driving.

You should pressure test the system to verify that you don't have a leak, too -- may only leak under pressure like the Volvo TC -- bad heater hose on the back of the head, only leaked when hot.

Peter
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1985 Volvo 740 GLE Turobodiesel 218,000
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Old 03-06-2004, 03:01 AM
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Bad cap?

When I take the cap off after running the engine, there's a slight gas escape, but not much.

I'm very certain the thermostat was inserted correctly, as I just put it in exactly the way the old one came out. I'm not so sure it fits the other way, but you could be right.

I'm surprised to hear that sometimes they're junk right out of the box. Should I just go with an MB original, or are they just as bad?


Thanks!
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Old 03-06-2004, 07:15 AM
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Bad cap - Yep

I had this exact same problem with my 93 400E. I was losing coolant but could not find any evidence of leaking. To make a long story short it ended up being a bad coolant tank cap. When the rubber seal on the cap gets brittle it does not seal well - when the car heats up and the cooling system builds up pressure coolant will escape past the cap and down the drain tube.

On the W124 cars this escaping coolant is a hard thing to spot because there is ANOTHER coolant overflow tank located inside the front fender. (at least there is on a 93 400E) This tank has an obscure drain hole and for some reason my car would only leak while it was running, and even then not too often.

I was finally able to isolate the problem by building a homemade cooling system pressure tester. My cap was leaking at more than 5 PSI pressure. A new cap fixed the problem for good.

Good luck - Tim
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Old 03-06-2004, 02:23 PM
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I think you might be correct. Now that I think of it, on the top of the overflow thank, there is a little dimple in the plastic that always has anti freeze in it, and I couldn't figure out how the hell that was getting there. It's probably what's left over after the coolant overflows past the cap. I think I'll invest five bucks in a new cap.

Is there any point in getting one with a higher rating (more PSI, or whatever)?
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Old 03-06-2004, 02:45 PM
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No, just get a new OEM cap. You can inspect the rubber seal on your current cap, if it is cracked or brittle replace this is almost certainly at least one of your problems.
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Old 03-06-2004, 02:52 PM
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...one of my problems? Hey, now, let's not get personal. It's taken me years of therapy to make it this far.

Seriously, thanks for the tip. I'll check it out.
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  #11  
Old 03-06-2004, 03:55 PM
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I leave my cap loose even on the cars without Evans Coolant. As long as they don't get to the boiling point, where's the problem?

P E H
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  #12  
Old 03-06-2004, 04:41 PM
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So don't tell me let me guess.....

He is wasting his money buy replacing the radiator cap?
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Old 03-06-2004, 04:58 PM
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Tim,

Could be.

P E H
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Old 03-06-2004, 07:12 PM
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Whoa- wait a minute!

I didn't buy one yet. Are you suggesting it could be something else? I went out and looked at the seal on my cap, and it didn't look all that bad.

What's your theory?
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  #15  
Old 03-06-2004, 07:25 PM
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Gil:

It's a bad cap. Only blows coolant out when at operating temp. They look fine, but the spring is collapsed, so they open at low pressure, the coolant boils, and burps liquid coolant out the overflow tank.

I've replaced a couple now for that very problem -- worse in hot weather. The TE would be fine unless you drove it with the AC on in the summer, and then wasn't a problem til you stopped. Then it burped up a quart of two of coolant every time you shut the engine off.

New MB cap holds 20 psi.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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