Author Topic: Heat exchanger questions (Read 20186 times)

waqas · « **on:** July 02, 2009, 02:09:51 »

I finally took out the spare heat exchanger from my 1967 250SE parts car. I didn't have a 27mm crowfoot handy at the time, so I took out the entire assembly including the oil filter housing (see pics).

I noticed that one of the high-pressure oil lines was not rigid all the way, as in my 1966 250SE (and all other photos I've seen of the heat exchanger setup in other M129 engines).

Is this original? I presume it was done to alleviate the stress caused by the rigid lines on the exchanger itself.
Does anyone have a part number for the replacement flexible high-pressure hose shown connected between the two rigid lines?

I plan on having this unit pressure tested before I attempt to change out my leaky unit. Are these pressure numbers correct for testing?

20psi on the water side
100psi on the oil side

waqas · « **Reply #1 on:** July 02, 2009, 03:38:48 »

For reference, Naj posted the great picture below of the older setup in this thread: http://www.sl113.org/forums/index.php?topic=4940.msg31119#msg31119

As shown, the lower oil line is rigid all the way from the oil filter housing to the heat exchanger.

Dave Gallon · « **Reply #2 on:** July 02, 2009, 08:32:51 »

Of course, the 250SE and 250SL use an M129 engine. The M129 parts catalog (Edition B, January 1967) shows the following for this oil path:
127 180 00 27\
127 180 02 27 | all replaced by
198 180 01 82 /
127 180 03 27
The rigid pipe you normally see is 127 180 03 27 and this is the part specified for this application. However, don't give up ...

I will be talking about this at the PUB but note how three of the four part numbers are of the form: XXX 180 XX 27 while the other part number is of the form XXX 180 XX 82. Now, the first clue is that something like XXX 180 XX 27 is a metal tube related to oil while something like XXX 180 XX 82 is a hose related to oil, so 198 180 01 82 is some sort of hose part. Next, the 198 indicates the part was originally made for the 300SL (either Gull Wing or Roadster). A quick glance at the 300SL Roadster parts book shows that 198 180 01 82 is an oil hose and is exactly the center portion of the assembly you show. Further, we can make a reasonable guess that 127 180 00 27 and 127 180 02 27 are the metal tubes on either side of the hose. The metal pipes appear to be unavailable (no surprise!). However, 198 180 01 82 appears to be available, has a June, 2009 US suggested list price of $31.00 and a suggested wholesale of $25.00. By the way, the Electronic Parts Catalog for the M129 has eliminated this note of replacement making it extremely difficult to identify the hose.

Please send me a private note if you would like me to check MB stock and for my price on this part.

waqas · « **Reply #3 on:** July 02, 2009, 12:39:47 »

Wow, thanks Dave! Looking forward to your presentation at PUB.

So what you're saying is the the full rigid line came after the 3-piece setup? That would imply that the rigid line is superior to the 3-piece setup in some respect, according to Daimler-Benz.

The typical failure pattern of these heat-exchangers is caused by these properties:

the exchanger and the rigid lines are made of dissimilar metals (with dissimilar rates of expansion and contraction)
the mounting point is near the center of the exchanger, but the rigid lines attach near the ends of the exchanger (lever action)

Repeated cycles of excessive engine temperature coupled with the above might lead to intense stresses around the center-mount point, possibly leading to cracks/leaks around there.

So I would have thought the 3-piece setup might reduce the chances of failure/leaks in the heat exchanger.

If the full-length rigid line is correct/better, then I'm inclined to leave it that way.

Dave Gallon · « **Reply #4 on:** July 02, 2009, 19:02:59 »

Yes, the full length rigid line came second.

At times, every engineering organization has made mistakes. Sadly, Daimler-Benz AG was no different than anyone else in this respect. I have no way of knowing why the change. One can guess at reduced production cost, eliminating hose failures, etc. It seems to me that the early version with separate hose is the superior solution. It would be difficult to retrofit because the two individual pipes are not available but, as you already have them, I believe I would stick with the hose solution and maintain some flexibility in the connection.

Dave Gallon · « **Reply #5 on:** July 02, 2009, 19:44:37 »

I have to laugh at myself just a little bit. I realize this morning that there is nothing difficult about finding the part numbers for the individual pipes and hose, just look at the 230SL parts book ...

waqas · « **Reply #6 on:** July 03, 2009, 00:01:07 »

Bad news: the heat exchanger from my parts car is also leaking. The crack can clearly be seen in the center of the second picture.

66andBlue · « **Reply #7 on:** July 03, 2009, 01:01:22 »

Waqas,
perhaps this might help identifying the different parts a bit better.
A good radiator shop should be able to solder the crack in your spare?

waqas · « **Reply #8 on:** July 03, 2009, 01:28:27 »

Alfred, thanks for the great information. As usual, your figures are top-notch.

The radiator shop is already on it. Will post pics as I make progress. The key is not to simply patch it, but to dismantle and re-assemble with new solder all around the main central seam.

I also removed my unit (pic) and gave it to them to also fix up. (spares are good!)

waqas · « **Reply #9 on:** July 03, 2009, 19:10:35 »

In case anyone was interested in what these things look like from the inside....

Dash808 · « **Reply #10 on:** July 04, 2009, 09:20:02 »

Thanks Waqas and good timing. I was just inspecting mine an hour ago. I think it's safe to say we are always interested in seeing the insides of things.

graphic66 · « **Reply #11 on:** July 04, 2009, 18:43:33 »

Would a heat exchanger from an M129 engine fit on an M127 engine without one stock? I have a 66' 230SL and an 67' 250 SL parts motor. It may be a nice retrofit if iit would just bolt in. I know that there is no simple jobs on these cars though.

waqas · « **Reply #12 on:** July 04, 2009, 19:02:47 »

Quote from: graphic66 on July 04, 2009, 18:43:33

Would a heat exchanger from an M129 engine fit on an M127 engine without one stock? I have a 66' 230SL and an 67' 250 SL parts motor. It may be a nice retrofit if iit would just bolt in. I know that there is no simple jobs on these cars though.

These heat exchangers were originally optional equipment on the 230SL, so they will bolt right in. You should collect all the items in Naj's picture in this post: http://www.sl113.org/forums/index.php?topic=4940.msg31119#msg31119

Make sure you have the heat exchanger pressure tested at a radiator shop (20psi for the cooling side and 100psi for the oil side). Also, make sure the oil passages are completely free of debris-- mine is a bit clogged and the radiator shop is boiling it out.

Via Manci · « **Reply #13 on:** July 05, 2009, 01:12:57 »

Quote

perhaps this might help identifying the different parts a bit better.
A good radiator shop should be able to solder the crack in your spare?

I have the book with the pictures of the parts and a # for each part. Where did you get the block numbers shown in the pictures?
Thanks for your patients

Naj ✝︎ · « **Reply #14 on:** July 06, 2009, 18:32:10 »

Quote from: graphic66 on July 04, 2009, 18:43:33

Would a heat exchanger from an M129 engine fit on an M127 engine without one stock? I have a 66' 230SL and an 67' 250 SL parts motor. It may be a nice retrofit if iit would just bolt in. I know that there is no simple jobs on these cars though.

Yes, it woud, provided you have all the rest of the plumbing.
The hardest part for me was to remove the blanking plug from the engine block with engine in-situ.
I had to drill maybe 15 small roles round the circumference of the plug and then break it out. You might want to get a new adaptor to replace the plug rather than try to remove one from the 129.
I did not try heat!

naj

waqas · « **Reply #15 on:** July 07, 2009, 04:57:06 »

Got the heat exchanger back from the shop. Cleaned it up and degreased ready for painting.

My latest questions:

Is the heat exchanger mounted between the engine block and the motor mount arm, or is the motor mount arm between the engine block and the heat exchanger? (I think I recall seeing both configurations)
What is the correct finish for the heat exchanger? (satin black like the radiator?)

DaveB · « **Reply #16 on:** July 07, 2009, 09:38:06 »

From memory I did not have to remove the motor mount when removing my heat exchanger therefore the heat exchanger must have been outside the motor mount.
Mine is a low gloss black (under the grime).
David

mbzse · « **Reply #17 on:** July 07, 2009, 11:42:38 »

These devices were flat black like the radiator and expansion tank, yes.
They fit outside of the motor mount (not directly against the block)

What happens with age is that the solder joints will degrade and become porous - hence the units crack and
coolant leaks become an issue...
So, not much use mounting a used unit onto a car - they need to be re-soldered first, just like you did Waqas
/hans in Sweden

Quote from: waqas on July 07, 2009, 04:57:06

Got the heat exchanger back from the shop. Cleaned it up and degreased ready for painting.
My latest questions:
Is the heat exchanger mounted between the engine block and the motor mount arm, or is the motor mount arm between the engine block and the heat exchanger? (I think I recall seeing both configurations)
What is the correct finish for the heat exchanger? (satin black like the radiator?)

rogerh113 · « **Reply #18 on:** July 07, 2009, 13:43:48 »

Just out of curiosity, why are you putting the heat exchanger in?? Do you have an overheating problem? It seems that they are somewhat failure prone, and having coolant and the lubricant (oil) in immediate proximity in a cannister that might allow them to mix freely sounds a bit risky. Probably why MB moved to an alternate design with the later 113s. My car is a driver, and I disconnected the heat exchanger early on at the recommendation of my mechanic (he was not amused when he saw it sitting in there). The car warms up a bit on longer high-speed freeway runs, but not to any significant extent. I think that if I really needed oil cooling, I would look into a retrofit of the later oil cooler. Unless, of course, yours is a show car and has to be stock.

Regards -- Roger

waqas · « **Reply #19 on:** July 07, 2009, 14:48:00 »

Folks, thanks for the answers!

Roger, I'm putting it back in because I think my car needs it in the Texas heat (the past few weeks the temp here has been 100F+). In addition, my car [allegedly] has AC. (still need to reinstall it once I'm done with all this other stuff). In order to switch to the air-cooler setup from later cars, I would need a radiator from a 280SE/coupe before the changeover to the low-grille coupe design (I think the radiators are different). In any case, I'm also adding a heater bypass to increase the flow from the back of the head during summer months.

As far as the heat exchanger being "prone to failure", I can't really say much except that everyone I've talked to (those who've had the same issue) has reported coolant leaks on the outside (not an internal leak between the oil and water passageways). Also, a couple folks have reported a repeat failure, and at least in one of those cases the repair was done without re-soldering the entire seam (don't know details about the other). I decided to have it completely de-soldered before re-soldering the seam along the entire perimeter. If a re-soldered radiator can hold, then so should this. (knock on wood!)

Regarding the design change, I really don't know for sure why MB changed over to the air-cooler setup. However, the heat exchanger (in M127 and M129) has a dual function of (1) heating up the oil quickly, and (2) keeping it cool after it has heated up. In the M130 cars, my guess is that heating up the oil quickly was much less of an issue than keeping it cool. Therefore, they went with just an oil air-cooler instead of an exchanger. The location was probably changed because an air-cooler is much more effective where there is a good flow of air with a greater surface area (hence, right beside the radiator).

Benz Dr. · « **Reply #20 on:** July 07, 2009, 17:13:38 »

The best of the three cars is the 250SL. It has a larger rad than the other two and the oil cooler. You can't beat that for running cool.

The failure of the heat exchanger is greatly exagerated. I stuck one on my car without doing anything to it and it's been woorking for 15 years. I've never seen one leak or fail so I have no problem trusting them. There is zero reason why they would fail any sooner than the rad out in front of the engine.

rogerh113 · « **Reply #21 on:** July 09, 2009, 01:55:02 »

Waqas,

Sounds like a well considered solution. Best of luck, and I hope any failure is soft.....

Regards -- Roger

waqas · « **Reply #22 on:** July 10, 2009, 16:34:00 »

Anyone know the torque required for tightening all the oil lines to/from the heat exchanger to the oil filter housing?

waqas · « **Reply #23 on:** July 10, 2009, 20:37:19 »

Painted and ready to go back in. One coat of POR-15 and one of satin black enamel.

Also shown are the fuel pump mounting brakcets, shroud, battery bracket, heater box front cover, power-steering pump pulley, air intake housing, heater pipes, etc.

Dash808 · « **Reply #24 on:** July 10, 2009, 22:19:55 »

That came out great, Waqas.

Did you brush or spray the POR-15? I assume brush but just wondering because the finish looks nice and smooth on the brackets and heat exchanger. Or maybe it comes in a spray can now?

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Author Topic: Heat exchanger questions (Read 20186 times)

graphic66

Via Manci