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  #1  
Old 09-23-2002, 09:59 AM
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New 95 E320 Hd Gasket - Runs Hotter Now

I had an independent shop replace my leaking head gasket (M104 engine) . When I got the car back, it seems to run hotter at low engine rpm (and speed) as measured by the temp gauge on the dash. Head was re-conditioned including valve job. Also timing chain was replaced.

At 60 mph, temps are normal (outside temps to 90F), right around 90C, but when I stop, temps climb toward 100C or beyond, even at outside temps as low as 45F. They go down again at cruise.

Is it possible to mis-install a new head gasket so that coolant passages to the head are partially blocked/obstructed - or is it self aligning. Work was done at a very respected shop specializing in MBs.

I have checked all the usual things, thermostat, radiator obstructions, etc and all check good. Before the head gasket replacement, temps did not climb like they do now after stopping, and I am looking for advice before I go back to the shop. I have driven about 5 kmiles since the repair. Temps never get high enough to kick on the aux fans (107C).

Or am I just paranoid?

Thanks

Tom Latos
95 e320 nubie, 115 k miles
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  #2  
Old 09-23-2002, 10:49 AM
DTF
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Cheap trouble shooting tip is to replace the coolant tank cap first. If the system won't hold pressure because of a bad cap (I couldn't tell mine was bad by looking at it) the water/coolant mix will boil at a lower temp reducing cooling capabilities.
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  #3  
Old 09-23-2002, 12:36 PM
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your thermostat may be showing it's age. i had the same symptoms after HG job, then the temp swings got more noticeble so i replaced the t'stat which made the temps a constant 90-95C. i'm running with an 83C thermostat now which makes it run a little cooler at around 85-90C.
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  #4  
Old 09-23-2002, 12:43 PM
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Runs hotter now

Both suggestions already done. Coolant tank cap replaced with new and new thermostat (87C) installed. No impact on observed temps.

Tom Latos
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  #5  
Old 09-23-2002, 01:24 PM
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mine was same way, in winter with stop and go traffic, my temps went over 100C. with the 83C thermostat - it may still do that but it will take a bit longer. i also have the resistive cooling mod installed which just stops it before it goes over 100C...
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  #6  
Old 09-23-2002, 01:38 PM
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If the temps go down at cruise, it is generally reasonable to assume it is related to airflow ... i.e. not likely head gasket or it would be a problem all the time, right?

Lack of air flow at slow speeds (particularly in low ambient temps) points to vclutch on fan not operating properly ... assuming all else is OK. At that kind of ambient temp, the efan should almost never even get an opportunity to meet the temp limit for operation.

I guess there is some potential that head gasket was badly done and the (1) exhaust gases are leaking into the coolant (can tell with instrument to detect hydrocarbons, I think ... can't remember what it is called), (2) some coolant passages were blocked by the gasket itself.
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #7  
Old 09-23-2002, 02:21 PM
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Hi Tom- a few thoughts for you

>you should have 2 stage (aka- speed) fan- suggest reviewing relay/ resistor system to ensure that low speed and high speed engage as intended by MB

>good previous suggestion- to have viscous reviewed

>may need a new rad itself or chemical flush

good luck and let us know what turns out- - (most common cooling issues are usually very easily sourced and addressed w/o much $$$)

best regards
-fad
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  #8  
Old 09-23-2002, 02:53 PM
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-fad is absolutely right ... I left the radiator out as a separate issue, however, it is pretty clear that, if the radiator is not operating efficiently, that the increase in airflow might be enough to overcome a lack of efficiency ... however, this seems a longer shot in 45F weather ... the engine should have a VERY hard time overheating in this kind of weather.
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #9  
Old 09-23-2002, 03:00 PM
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It is not uncommon after cooling system related work to
find that the anti-freeze mixture percentage has been changed.
This is something you may want to check.
A 50/50 concentration is what you are looking for. [ less in mild climates]

Many times after the system has been opened , it is topped off with straight A/F without concern....thus changing the cooling properties..
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  #10  
Old 09-23-2002, 03:12 PM
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Thanks for the good suggestions. Here is more of my views:

Onset of hotter operation was coincident with head gasket repair.

Fans are a-ok. Two speed operation as controlled by both high/low speed relays (w/wo dropping resisitor) are working - low speed kicks-in on A/C pressure switch command.

Examined interior of radiator at inlets - looks clean with no visable corrosion or gunk build-up.

Coolant quality is very good, no evidence of combustion products.

All engine compartment baffels are in-place and tight.

Is it possible to mis-align head gasket on installation? Is there an expected break-in period (with increased heat rejection to the coolant) after a top overhaul and head gasket?

Maybe this is not a problem, but it's different than before the repair.

As to the Vclutch, a search of the archives indicates that this is rarely a problem - but of course it had to come off to do the repair - is it easily damaged with dis-assembly?

Tom Latos
E320 nubie 115 kmiles
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  #11  
Old 09-23-2002, 03:30 PM
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<>

Did they have to shave the head ??
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  #12  
Old 09-23-2002, 04:24 PM
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I called the shop that did the repair, and of course the machine shop work is outsourced. The chief mechanic stated that if there was a warpage condition on the head that dictated excessive material removal, they automatically get the call. That did not happen for my repair. Normal proceedure is to remove very little material. He also stated that the head gasket is alligned on dowel pins, and can't be installed misalligned.

The chief mechanic wondered allowed about the V-clutch, and stated that there is no good way to test it. And just like the archives state, replacement very rarely solves a cooling problem.
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  #13  
Old 09-23-2002, 04:27 PM
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And I changed the coolant when I got the car back. Installed a 50/50 mix of MB stuff.

Tom Latos
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  #14  
Old 09-23-2002, 04:36 PM
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Tom,

Sounds like you are down to:

1. Bad radiator (corrosion may not be evident) as most expensive I would consider it last
2. Bad viscous clutch - also a very expensive item if someone else does the work ... can trouble shoot by locking it up by bolting the fan blade to the assembly, but, if bad, it will cause overheating at slow speeds
3. Thermostat - I know you said you put in a new one, but if you have done searches on tstats you will find they are very unpredictable - very cheap to replace, especially if you are doing it yourself ... try another one from another manufacturer and source

Me? I would start with tstat and don't change anything else. If that doesn't do it, then lock up the vclutch on the far and see what happens. Radiator is last ... and, expensive ... try getting a used one and giving it a try ... R and R is not all that hard.

If these don't do it, it has to be either a pressure issue (sounds like you believe coolant system is absolutely tight and since it isn't boiling over, I don't think that is it either); or, a head gasket problem.

Try the tstat - a lot of folks have been very surprised to find their new tstats don't work.
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George Stephenson
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg
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  #15  
Old 09-23-2002, 05:22 PM
moedip
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I have been told that if the viscous fan assy is removed and not stored upright - the fluid could leak out and cause the fan not to work. Try giving the fan a spin with the motor off and see if there is any resistance - if there is none - that could be the problem. Just a thought.
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