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Old 07-06-2001, 03:12 PM
450 SLC 5.0
Posts: n/a
This may seem like a dumb question, but I have to ask. I changed the water pump and thermostat plus flushed the cooling system in my girlfriend’s 300 diesel (turbo engine with 200K on it) a month ago. It now shows just the very smallest wisp of oil in the expansion tank. There is probably less than one drop worth of it in there, and it is definitely oil NOT transmission fluid. (I blotted some up with a paper towel and it is not red.)

I know what this means: head gasket time. But there is no coolant in the oil, in fact the cooling system holds pressure in it overnight (strange?). There is no coolant in the transmission fluid either. In fact, there is no coolant loss at all. The car does run warm, about 95-100 degrees in hot weather with the air conditioning on.

But I was wondering if there is ANY chance at all that re-torqueing the head bolts might even have ANY chance at sealing it back up? Is it worth trying, or do I even have to worry about this small of an amount of oil? I hear about diesel’s leaking, but I always assumed that means external, not internal leakage.

Thanks for the help everyone!

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Old 07-06-2001, 04:22 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,504
These bolts are not designed to have to be re-torqued.
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Old 07-06-2001, 05:16 PM
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Join Date: Dec 2000
Location: Fairfax County, Virginia
Posts: 856
Interesting question - logical. However, depending on the types of bolts used, this could be an interesting test, or a disaster.

I understand some bolts are designed to stretch at the appropriate torque ... they are actually longer than a new one when removed from the head to block interface.

I have the same basic problem on an old mini-van ... would like to experiment some, but even then ...

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Old 07-07-2001, 12:10 AM
Posts: n/a
Did you take the front cover off (the one with the two o-rings) for any reason while changing water pump? I am not sure of the water pump configuration on a diesel but I'll bet you can find an independent service shop somewhere that can answer your questions as to the possibilities. Wish I could help. Good luck.
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Old 07-07-2001, 02:55 PM
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Join Date: Aug 2000
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Posts: 858
Interesting. My new baby (84 300D, 199,000) acts in the same way in regards to the “(strange?)” cooling system pressure characteristics that you mention.

When the engine is warmed up, the level in the expansion tank drops – I was assuming that it is due to the expansion of the hoses & resultant increase in their volume/capacity.

However, like yours, it holds pressure overnight; the hoses are still firm (pressurized) in the morning. If I open the expansion tank cap in the morning, the system gurgles quite a bit & the level in the tank goes back up to normal. My other (gasoline engine) cars do not do this, so I am concerned about this being ‘normal’ or not. I hope that someone can chime in on this?


By the way, I am not sure if the 617.95x engines use stretch bolts or not. But remember that IF they do, stretch bolts cannot be reused, they must be replaced. As far as re-torquing the head to eliminate a leak, depending upon the circumstances, it MAY work temporarily, but I wouldn’t consider it a proper cure even if it does work.
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Old 07-07-2001, 06:36 PM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
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RTH - my '95 300D does it too. I am not losing coolant and the oil consumption seems to be pretty normal - 1 qt between 3k mile oil changes so I don't worry about it.
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Old 07-16-2001, 03:54 PM
450 SLC 5.0
Posts: n/a
Just thought I would give an update. I decided to go for broke and re-torque them since I would have to pull the head anyways. Unless I get rid of this girlfriend also.

I have not seen any more oil in the coolant, just a little left over stuff floating around. I don’t know how long it will hold, but I have my fingers crossed. I will keep yyou posted!
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Old 07-17-2001, 10:21 AM
G-Benz's Avatar
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Join Date: Apr 2001
Location: Dallas/Fort-Worth
Posts: 5,711
You probably haven't done much to the bolts it you're talking about 1/4 to 1/2 of a turn or so for each bolt. Maybe even squeezed the head down just enough to keep that trickle of oil from getting past the water jacket.

If you ever decide to LOOSEN them for whatever reason, and then re-torque, you are going to be in for a blown head gasket for certain.

Had a Chrysler Conquest with the same type of head bolts. Did some head work, and replaced the head bolts with new APM head bolts, designed for the one-torque applications only. Other owners of similar models continued to have recurring head gasket failures because their mechanics would reuse the head bolts.

Lesson learned.

2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car
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