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  #1  
Old 02-03-2006, 10:16 PM
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overheating in winter

Hi, enjoy reading all the messages this site is a lot better than i was getting with Audi`s. here is the problem. have a 79 300d when the temp drops to -20c i have this problem will driving on the hwy for about 15 min heat is coming from the heater then i notice it is blowing cold air, and the temp guage climbs quickly to the max temp. i pull over and i have found by releasing the theromstat bleed srew but taking it off and letting it sit for 5 min the temp resumes to normal driving temp. what i have checked:1. rad has bee pulled and is good working order.
2. the water pump and thermostat have been checked and are working.
i seem to be creating a air lock somewhere could it be the head gasket? the oil looks fine no indication of contamination. by the way i live in Brandon, MB Canada. if the temp is above -10 i have had no problems. there is one item i have had to take out because it was seized was the aux electric water pump havent put it back

Clive

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Old 02-03-2006, 10:31 PM
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Welcome to the forum.


The loss of heat, simulataneously with the rise in temperature certainly points to air in the cooling system. Now, whether the air is simply there from the last flush and fill, or whether combustion gases are charging the cooling system, is the question.

Some questions/tests:

1) Has the cooling system recently been opened/flushed?

2) How often to you add coolant to the expansion tank to maintain level? After driving for some distance, is the level in the tank down about 8 oz. or so, the next morning?

3) After allowing the vehicle to sit overnight, after running it hard, open the hood and sqeeze the upper radiator hose. See if you can squeeze two fingers together. Make a mental note of the stiffness of the upper hose. Then remove the cap on the expansion tank and observe if any pressure releases. Now squeeze the upper hose, again, and observe any difference in firmness from the original test.

Your answers to these questions will assist us in solving the problem.
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Old 02-04-2006, 04:20 AM
t walgamuth's Avatar
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clive

did you say you are running without the auxiliary water pump?

i think that directs flow to the heater core when the car is warming up. at -10 you may be in warmup mode all day. so i would get a new or used aux pump and put it in and see if that doesnt solve the problem.

tom w
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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.
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Old 02-04-2006, 08:34 AM
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Do diesels produce enough CO to detect it at the coolant tank?
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Old 02-04-2006, 11:03 AM
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thanks for the replies, i have noticed how long the pressure stays in the bottom rad hose but i will check today. about the aux water pump i was wondering if that would make a difference at hwy speed, i thought it was more to help at idle and around town when the revs are not high enough with the main w/pump. my cat doesent have a overflowtank it just exits to the ground, that mod must have come later? the car has 420,000k and 200,000 on a replacement engine.
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Old 02-04-2006, 11:13 AM
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Quote:
Originally Posted by CCPB
my cat doesent have a overflowtank it just exits to the ground, that mod must have come later?
Yes, that's certainly possible. In such a case, just use the radiator cap instead of the cap on the expansion tank (not present).

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