cooling

[peterm]

another 90 degree day in NY and I won't be driving the pagoda-  makes me think has anyone been successful with aux electric fans?  if so which one and how difficult was the conversion?

http://www.innerauto.com/store/products.php?year=1971&make_text=mercedes_benz&model_text=280sl&category=cooling_system&subcategory=electric_cooling_fan

[Rolf]

I live in New Jersey and have been driving mine without any problems with the temp. Have you taken a look at the thermostat, water pump, clogging in the radiator, hoses? The temp in mine has been around 180 deg no matter if I'm driving around town or on the highway. Has the system been flushed any time recently?

Rolf
1966 230SL Auto
1992 300D
1991 FLHS

[peterm]

recored radiator, shroud in place, new water pump, fan clutch, timing change water wetter, thermostat replced etc etc  been driving with the heat on in traffic for 2 years.  my ac does blow cool except can only use it at highway speed

[enochbell]

Hate to raise this spectre, it may have been very rare and isolated, but before my engine rebuild I had an overheating issue.  When I pulled the head, it revealed a temendous amount of corrosion and scaling in the coolant channels, enough so that the channels were probably very inefficient.  I ended up replacing the head (short block was OK).  I hope that is not your issue, but maybe others have had experience?  The rebuild and new head cured the problem, but I don't know how or why.

Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[peterm]

that makes me happier, sounds like my engine needs an endoscopy but I've heard that cooling was always an issue with many of the air con cars right off the bat, and that some resorted to electric fans

[doitwright]

Mercedes made a retrofit kit to allow a bypass of the heater core.  It seems that without the heater valve open, coolant does not flow through the head.  Others on this site have talked about a DIY solution that meerely introduces a T fitting spliced into the hose at both the inlet and outlet on the engine compartment side of the heater core.  This will allow continuous flow of coolant when the thermostat is open.  I am planning to make this mod on my car using a 1/2" copper T plubing fitting and a valve.

Frank Koronkiewicz
Willowbrook, Illinois

1970 280SL Light Ivory

[jeffc280sl]

I've been using the heater core bypass hose for about a year.  It works great and I recommend those who have an habitual problem giving it a try.  Its one of the least expensive mods you can make to your car with a potential for big savings.  I think the T fittings work best.  The hot water is under pressure and as it flows towards the T it meets a 90 degree turn facilitated by the closed heater core valve.  Water circulates over the head to the heater core return line and all is good.  When you want heat, open the valve as per normal and water will rush by the T and in a staright line head for the heater core.  Thru the heater core to warm the cabim and out to be recirculated.  I don't drive mine in the winter so I can't say how effective the mod is regarding cabin heat.  I do drive on cool days in March and the heat is just fine.  If you do drive in the cold of winter a simple manual stop valve in the bypass hose will make sure all water flows to the heater core.

Jeff C.
1970 280SL 4-speed

[nick350]

david brough has one fitted and has posted pictures on this site, have a look.

[DavidBrough]

Hi Peter,

I did have an auxiliary blower fan fitted to the front of the radiator and it worked very well but I had to remove it when I recently fitted A/C. I have now ordered a SPAL suction fan and plan to fit it in place of the existing viscous unit.

In the meantime I fitted the heater bypass pipe referred to earlier and whilst it keeps the engine cooler on the move it doesn’t work for me when stationary so I do need to try something else. I am hoping that the SPAL unit will work and plan to have a thermostat fitted directly into the radiator core to switch it on and off. I will post progress when the unit arrives.

David Brough
1969 280SL Auto with A/C

[Benz Dr.]

You could try the auxillary water pump used on a 123 or 126 sedan. They're designed to move coolant into the heater core when the car is at or near idle speed. Might be just the ticket. You could probably wire it into the throttle solenoid circuit if you have an auto so it only runs while sitting at a stop light or stop and go traffic.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[hill]

quote:Originally posted by jeffc280sl

I've been using the heater core bypass hose for about a year.  It works great and I recommend those who have an habitual problem giving it a try.  Its one of the least expensive mods you can make to your car with a potential for big savings.  I think the T fittings work best.  The hot water is under pressure and as it flows towards the T it meets a 90 degree turn facilitated by the closed heater core valve.  Water circulates over the head to the heater core return line and all is good.  When you want heat, open the valve as per normal and water will rush by the T and in a staright line head for the heater core.  Thru the heater core to warm the cabim and out to be recirculated.  I don't drive mine in the winter so I can't say how effective the mod is regarding cabin heat.  I do drive on cool days in March and the heat is just fine.  If you do drive in the cold of winter a simple manual stop valve in the bypass hose will make sure all water flows to the heater core.

Jeff C.
1970 280SL 4-speed

Pictures any one ? Please.

Happy Benzing
Darryl, Hill
350 SL4.5 #60
1967 250sl "California"

[Willis69]

Peter - I too live in NY(Manhattan) and have also had problems w/ my thermometer indicating the engine is too hot while I'm in slow traffic or idling.  It goes way past the red "too hot" indicator, and has twice maxed out the thermometer.  I always wory that after running it for an hour or two on the NJ freeways or LIE that I'll get to the traffic at one of the tunnels and stall out whilst in there.  I have a '71 280 Sl, and factory installed air-conditioning which I never use.  Do you have problems w/o using the air-conditioning too or does it just get too hot w/ the air-con on?  How long can your car run before it starts getting too hot?  Thank you.

[jeffc280sl]

Here a pic of the heater core bypass.

Download Attachment: Bob Bypass 001.jpg
57.44 KB

Jeff C.
1970 280SL 4-speed

[hill]

quote:Originally posted by jeffc280sl

Here a pic of the heater core bypass.

Download Attachment: Bob Bypass 001.jpg
57.44 KB

Jeff C.
1970 280SL 4-speed

Thank you very much. I will do the same with a valve on the bypass. I really like top down driving on a crisp morning.

Happy Benzing
Darryl, Hill
350 SL4.5 #60
1967 250sl "California"

[jeffc280sl]

Hill,

So you don't mess up the MB hoses I went to a local parts store and in the back picked out pre-formed heater hoses that matched the top and bottom bends I needed for the T fittings.  That way you can easily go back to factory later on if desired.

Jeff C.
1970 280SL 4-speed

[Dick M]

Does anyone know of any downside from making this bypass modification.  Jeff, good suggestion for T fittings.. just in case.

Dick M
1970 280SL

[jeffc280sl]

A partial answer to your question may be found in the similarities of the heater core bypass to the MB supplied kit.   The heater core bypass that I installed serves the same purpose as the MB kit.  My bypass and the kit both take hot water from the head and recircuale it.

There are mionor differences in implementation as follows.
1) I tap into the heater core outlet at the mid point in the head.  The MB kit taps into the thermo time switch outlet at the rear of the head.  The outlet in the rear of the head is quite a bit smaller in diameter than the heater outlet mid head.

2) My bypass returns to the heater core return line which feeds at the water pump for recirculation.  The MB kit return feeds into the lower radiator hose which then flows to the water pump.

If we assume MB looked at potential problem areas when designing their kit and went ahead there are very minor differences between the implementations.  I'd be interested to hear what others think.



Jeff C.
1970 280SL 4-speed

[hill]

quote:Originally posted by jeffc280sl

Hill,

So you don't mess up the MB hoses I went to a local parts store and in the back picked out pre-formed heater hoses that matched the top and bottom bends I needed for the T fittings.  That way you can easily go back to factory later on if desired.

Jeff C.
1970 280SL 4-speed

Thanks, I'll do the coat hanger trick and get some. Hill

Happy Benzing
Darryl, Hill
350 SL4.5 #60
1967 250sl "California"

[awolff280sl]

Hi all,
I'm new to posting on this forum. The wealth of info has been very helpful, thanks!
Question for Jeff C. on the heater bypass. Did you use a pair of 3-way PVC T valves that fit the hose size, and if so, where did you get them?
Thanks.
Andy W.

[jeffc280sl]

Andy,

I used 5/8" metal Tees I found on a website that specializes in parts for Corvettes.  I'm sure brass barb type Tees would work also.

Jeff C.
1970 280SL 4-speed

[zoegrlh]

I would consider a recore of your radiator.  Had mine done this past spring and have not had one problem with overheating.  There are new cores on the market now that will increase you cooling capacity, and still look factory orig.  I had the new capacity core installed and am very happy with the looks and the results.

[awolff280sl]

Jeff, Thanks. Before I think about proceding with this project, could you explain for me what is the advantage of the heater bypass over a properly functioning heater valve?

Andy
1969 280sl 4sp

[zoegrlh]

Andy,
I would think a "heater bypass" will not solve your problem.  I had a problem with a radiator on my Maita that was somewhat clogged in a couple of tubes, would overheat in 90 degree days in traffic.  If I turned my heater on full, the water would circulate thru the heater core and would lower the temp reading because the water was being cooled also by heater core.  As you can understand I replaced my radiator before summer's end.  Anyway, I would think there is no advantage to bypassing.  The water still has to be cooled.

Robert Hyatt
Williamsburg, VA.

1970 280SL, Red on Silver,4-speed, Euro spec, 1999 C230 Kompresser Sport, Black on Black, 1990 Miata, Black on Red, 5 Speed

[jeffc280sl]

Robert,

Certainly the heater core does provide a surface for heat to dissipate.  Along with this function it also routes hotwater out of a large port in the head and returns it to the cooling system.  I think most will agree the hottest part of our cars is in the head.  The bypass performs the hot water circulation action of the heater core without introducing heat into the cabin.  Something you don't need in the summer months.  It is similar to a modification MB designed for engine cooling.

Jeff C.
1970 280SL 4-speed

[Paddy_Crow]

Yes, that's more or less what a bypass does. It's actually the thermostat that's bypassed, not the heater core. It's just easy to use the heater lines to engineer it into the cooling system after the fact. When the heater valves are open, it will serve as a bypass. But when it's hot out, we don't tend to like heat coming from our heater cores so heater valves are designed to close off coolant flow when the heater is off. Newer engines have bypass circuits designed right into the water crossover castings.

Thermostats do not open until hot water is present around them. Without some leakage, it takes some time for the water in that part of the circuit to heat up. Meanwhile, the water trapped in the cylinder head can be boiling and exhaust valves/seats overheat very quickly.

Democracy is two wolves and a lamb voting on what to have for lunch...