240D Valve Adjust and Retorque of head

[Fisherman]

Once again I need help...
I have the CD coming but need to do some work today on the car.

It appears I have the 616 engine according to my manual? 1975 240D 115 body. Does this sound right or could it be the 615 engine or does it make a difference anyway?

Anyway, I have two settings to use .10 and .30. The .10 is for Intakes? I have read in great depth all of the threads (about 6 hours worth) on valve adjustments so I believe I have my plan well thought through on this.
The image attached is from my valve cover and seems to indicate two different settings for the valves based on engine temp. It seems odd though because the higher temp indicates a wider gap? Shouldn't this be reversed due to expansion of the valves when warmer?

Secondly, while I am in, I was thinking of retorquing the head as I have a minor water leak at #4. My questions are:
1. Does it make sense to try to retorque the head?
2. Will the bolts be so set already that I may fail miserably, i.e. snap a bolt or at least not get the correct setting due to the bolts being "locked" in place over time? Perhaps backing them first a quarter turn and then retightening?
3. What is the torque setting for these bolts?
4. Is there a pattern used for loosening and then retorquing?
5. I believe they are the hex key bolts that I see, what size are these?

Sorry for all the questions but I'd like to do this right the first time.

[franklyspeaking]

The first question about the valves is a good one. I believe the reason is that the head expansion is the reason you set the valves looser when hot. The rate of cooling of a piece of metal is proportional to its mass. Therefore the valves (light) cool quickly in relation to the head (heavy). Cast iron probably has a higher coefficient of expansion also. At any rate, the distance between the valve seat and the cam grows when hot and takes awhile to cool off, and the valves which cool quickly and expand less, become tighter when the head cools.

I don't have my manuals here to answer the second question about the specs. I would try tightening the head bolts and even resort to Bars leak to avoid taking the head off. But my guess is that may very well be what you have to do to fix it.

Good luck.

[leathermang]

Well, since you are wanting to work on it today I will offer my opinion on some of the items...

I only set valves when the engine is stone cold. The best mechanics I know of insist on this also...unless it is an actual emergency... and then just to get you home in order to do it cold.It is very hard to interpolate the expansion of the valves and most people don'r really know what temp a warm engine is anyway.. the critical factor being that if you get it wrong you almost certainly will burn up an exhaust valve... very bad kharma....

Playing the odds on the water leak,, very unlikely that will seal it up.... and if you have read the torque reading threads you know that after a bolt has been in a threaded hole for a while you really need to take a tap and run it into it and clean the hole and lightly lub the bolt in order to have confidance in the torque being correct...

Yes, if gunk has built up below the bolt , from years of small water leaking.. then you could break a head bolt and have to go through a lot of grief to get back to zero..

My books do not go back to cover the 1975 so I can't be specific on the other stuff..

However, there is a definite order in which you gradually tighten the bolts to secure the head. I go through the proper order repeatedly at 10 lb increments... but I am compulsive obsessive according to some... .... it only takes 6 minutes longer than other peoples methods and it makes me feel good.

Sorry I don't have more information more specific to you engine, but someone will, and good luck... Greg

1980 240d manual

[Fisherman]

Thanks for the quick replies.
I already did the Bars Leaks thing and it helped but did not stop the leakage, hence the thought of the retorque. I think I'll skip this tough... I've too many times started something simple and spent days fixing the one little thing that Murphy throws at you. You know, Murphy's Law about the last bolt is the one that is frozen or breaks.

[leathermang]

where is the water leaking TO ? into the cylinder or out the side of the engine ?

[Fisherman]

Side of the engine just above the number 4 exhaust port and it wa extending all the way to the back fo the motor but it could have been tracing to there.
It is now limited to just over the #4 hole and is a small (maybe one inch long) trace after running hard for maybe thrity minutes.
It is not signifcant yet and does not appear to affect the compression but this might turn into something a little more aggressive if I don't get to it.
I am planning on pulling the head but I have no time and need a vehicle right now so I am trying to work with what I've got.

[leathermang]

Probably the most important aspect is that it means your not running a pressurized coolant system.. so you really need to watch for overheating....

[Fisherman]

I thought of that too and took it on a spin up to the mountain the other day. It's a good 25 minutes of mixed hill climbs and mild upgrades and the car only got to about 185 (maybe a little less) on the gauge during the longest climb.
Do you know at what temp the aux fan kicks in? I would have thought it would kick on but it didn't as far as I could tell. In fact, I stopped at the top of one long hill and just let the car idle to see if it would heat up and kick on the fan and it did not.
The leak is not severe enough to lose coolant pressure immediately either. I can let it sit for up to an hour before it appears to have bled off enough to not spit hot water everywhere when i take off the rad cap. Brings up a good point though. I have not measured exactly how long it takes to lose the pressure. Maybe I'll try that just for reference.

[JimSmith]

Fisherman,

I have the manual for this car, and the engines go in the following cars:

615 in Model 220D (115.110)

616 in Model 240D (115.117)

617 in Model 300D (115.114)

The valve clearances are:

Intake: 0.10 mm at 20 degrees C; 0.15 mm at 60 +/- 15 degrees C with a note to increase another 0.05 mm at continuous temps below -20 degrees C that only applies to the intake valves

Exhaust: 0.30 mm at 20 degrees C: 0.35 mm at 60 +/- 15 degrees C

The increased clearance at the higher operating temperatures is to account for the differential coefficients of expansion of the valve materials and the rest of the valve train (edit added "train") and head materials.

There is a specific head bolt tightening pattern, and I can scan the image and post it if you like. To make sure you are doing something with a net positive result, you should back them off, remove and inspect, replace if too long or damaged, lubricate them, reinsert, and then sock them up to the torque specification in increments, one at a time, in the loosening sequence. If you loosen more than one at time, you make a condition for Murphy to enter the scene. If you just try tightening them, you may or may not budge the head bolt, but most likely you won't.

Overall, I would not mess with head bolt torque. It was ok once, it is not ok now, and has not been for some time and a number of thermal/pressure cycles. Head bolt torque checks and reapplication of the originally specified torque will likely do nothing to cure your problem. It seems your head gasket is damaged and torque will not cure that.

For future reference the torque is applied to the head bolts in three increments, 40 Nm (Newton-meters), 60 Nm, and 90 Nm, followed by a check to 90 Nm with the engine water temperature at 80 degrees C.

Hope this helps and good luck, Jim

[Fisherman]

Thanks Jim,
You confirmed my thinking on the retorque issue. Leave well enough alone.

As to the clearances I thank you. You didn't happen to make one of those valve patterns like I sawe in the other post i.e. I O O I I O O I I, etc...?

I can look at the manifolds but a cheat sheet never hurts.

Thanks again.

[JimSmith]

Fisherman,

On a 240D the pattern is Exhaust, Intake, Intake, Exhaust, Exhaust, Intake, Intake, Exhaust, or: "O I I O O I I O"

On a 300D the pattern is Exhaust, Intake, Intake, Exhaust, Exhaust, Intake, Intake, Exhaust, Exhaust, Intake, or:

"O I I O O I I O O I"

Hope this helps, Jim

[leathermang]

JimSmith, isn't there something about going to a specified torque then turning an additional 90 degrees... even a special tool from MB to measure that 90 degrees ? Greg

[engatwork]

leathermang - that is true for the later model cars with the stretch bolts. The earlier cars Jim is referring to did not utilize "stretch" bolts so they published the actual torque numbers.

[JimSmith]

Greg,

There may later technical bulletins if the gasket design or the head bolt design changed for the 1975 240D engine, but the manual I have is from late 1977, and makes no mention of the bolt stretching technique you described. It says recheck the fasterners after some 300 to 1000 km.

I know some of the later cars were built with head gaskets that no longer required the follow up torque check. I am not aware of the practice of backfitting such gaskets to the earlier cars, but think it would be a good idea. The head and block mating surfaces are likely ok for the newer gasket, but I would check the technical bulletins before I did that.

Jim

[leathermang]

Cool Jim, I said up front I did not have those manuals... MB is the only place I have seen that extra 90 degree deal so the picture stuck in my mind .... the later models call for that on the rod bolts also.... Greg