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  #46  
Old 05-31-2010, 04:46 PM
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No one has thought about the actual temp sensor on the head. It could be sending false readings to the gauge. Its a fairly cheap part i suggest you replace it just to be sure. They do act weird when they get old.

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  #47  
Old 05-31-2010, 05:20 PM
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Like the other guy posted earlier, check inlet and outlet temps with like a temp gun rented from an auto parts store differnece should be 10-15 degrees from top to bottom. If thats good its your thermostat. Sounds like its not opening or is stuck open alrdy. Your symtoms are changing and its the only part that changes. But I went with an OEM radiator and the new one that came had more cooling lines so it was "updated" as far as I can figure. I am pretty sure my 8 runs way hotter than your 6, although the radiator may be different there also. I dont think youre tranny could be overheating it but if its slipping who knows.
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  #48  
Old 05-31-2010, 06:47 PM
latief's Avatar
1993 300E 2.8- M104
 
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Failed to mention that the two plug temp sensor was changed recently also with a new Behr unit....i did that to assure a proper function of Aux fans....

I will do some investigative work and update.....
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  #49  
Old 05-31-2010, 07:45 PM
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Above 30Km's (20mph) per hour your fans - main or axillary become irrelevant. The cooling system relies on airflow through the radiator.

(a) So either you have a blockage of air through the radiator or a blockage of the coolant in the radiator itself.

(b) If neither of the above (a) scenarios then you have a coolant circulation problem. Go to a radiator specialist and get the system pressure tested. This will establish if you have a slight leak or circulation problem.

(c) Where I come from you can source a genuine Behr radiator for the same price if not less than the steeelbay Chinese specials.

(d) You have changed your thermostat twice - a Wahler and Behr. I'm not fond of the former however brand new should be O.K. With the new Behr unit you still have the same problems, so the thermostat should be eliminated as a problem. Make sure you have the proper MB gasket for the thermostat. Some of the gaskets supplied with off party units are less than optimal.

(e) Make sure your serpentine belt is correctly tensioned - right up to the correct shoulder on the tensioner gauge. Belt slippage can cause the water pump not to operate at higher revs. Your tensioner may have reached its end of life if you can't tension the belt properly
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  #50  
Old 05-31-2010, 11:04 PM
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1993 300E 2.8- M104
 
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Thanks Ivan for the great post (as usual )

So if my system looses pressure due to a hair-line crack in the radiator, will that cause the car to overheat since coolant is not being pressurized enough....???

The reason for the question is that today i saw a trace of white residue from the lower radiator hose (coming from where it attaches to the radiator)...it is not leaking even with the car on and the system pressurized, but could it be that at a certain point when pressure is really high it leaks a bit? will this explain the symptoms? i am talking about a very small leak here....

I appreciate the responses....
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Last edited by latief; 06-01-2010 at 12:07 AM.
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  #51  
Old 06-01-2010, 03:21 AM
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Quote:
Originally Posted by latief View Post

So if my system looses pressure due to a hair-line crack in the radiator, will that cause the car to overheat since coolant is not being pressurized enough....??? I am talking about a very small leak here....
You see that image above with the hairline crack in the coolant reserve bottle? That was enough to cause the to raise the temp of a M103 engine substantially - in very hot ambient temperatures - however I'm talking 115 degrees in the shad here not your ambient 85 degrees.

You have a new radiator even though off brand shouldn't have cracked up yet - even a real cheapie. The newer radiators have a stronger metal collar in the top radiator inlet to prevent cracking and break off.

Generally at ambient temperatures even with a little bit of coolant loss the airflow at speed and water circulation will keep the temperature down around ninety degrees. When the car is slowed and the airflow reduces then the engine heats up.
Your engine is up around 105 degrees at highway speeds at ambient 85 degrees. There is some serious problem there.

I.M.H.O. you cant screw around here you need this problem looked at before much more expensive damage possibly occurs.
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  #52  
Old 06-01-2010, 03:01 PM
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1993 300E 2.8- M104
 
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So i checked again now briefly. Coolant level is unchanged, the coolant leak i thought i had was not a leak....

What i just found out is that the back side of the water pump pulley is a bit slimy and gooey... but since i am not loosing coolant, what could that be? could the pump stop spinning at a certain point internally? i highly doubt that...

Man changing the thing is going to be messy job....it still has warranty though...
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  #53  
Old 06-02-2010, 10:53 AM
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Still trying to figure out what to do with this...

radiator hoses are both hot to touch while engine warm...i could not find any cold spots in the radiator.......

it seems that with extended periods of elevated engine rpm, the heat is the worse...

yesterday, i took it again to a nice state road cruising at 65mph, and with rpm at 2500...temps creeped-up towards the 105 mark roughly after 10 minutes of driving....

My question is: can a pump spin correctly on the outside (i.e pulley), but not spin enough on the inside (impeller)? anyone ever opened a pump and seen how it looks internally?

I prefer to change a radiator than do a pump change, but i might have to i guess just to be sure...
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  #54  
Old 06-02-2010, 11:18 AM
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What about removing the thermostat completely and see if it changes anything? Like this I would assume you should definitely NOT heat up that quick as coolant would be flowing freely with the power of the pump.
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  #55  
Old 06-02-2010, 11:38 AM
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If the water coming out of the radiator is (nearly) as hot as the water coming in, your water pump is working.

There are two things that can cause this.
1 Not enough air flow (blocked airflow of radiator or condenser)
2 Cooling capacity of radiator to low.

Rob
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  #56  
Old 06-02-2010, 11:54 AM
latief's Avatar
1993 300E 2.8- M104
 
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Quote:
Originally Posted by Rob Pruijt View Post
If the water coming out of the radiator is (nearly) as hot as the water coming in, your water pump is working.

There are two things that can cause this.
1 Not enough air flow (blocked airflow of radiator or condenser)
2 Cooling capacity of radiator to low.

Rob
Makes sense....I think i will get a radiator just to eliminate this problem all together

Isn't the radiator though blocked by default by the AC condenser?
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  #57  
Old 06-02-2010, 12:13 PM
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Have you checked the airflow?

Rob
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  #58  
Old 06-02-2010, 12:34 PM
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How do you check the airflow ?


thanks
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  #59  
Old 06-02-2010, 02:43 PM
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No you remove the radiator from the inside. It is dead easy shouldn't take more than 30mins. Just drain the coolant, disconnect two tranny cooler lines on left side, and 2 coolant hoses on the right side, one on the top. Remove metal clips on top and lift up. It really is that easy. Just remember to top up your tranny fluid after the engine is started.
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  #60  
Old 06-02-2010, 03:36 PM
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If you have the radiator out just look through it.
Otherwise not use a strong light behind the radiator.

If yo have a compressor just blow air through it (from a distance)

Also look at the condenser, it may block the airflow to the radiator.

Rob

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