Author Topic: Heat coming in thru the firewall  (Read 2552 times)

Mohan58

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Heat coming in thru the firewall
« on: August 03, 2021, 14:28:17 »
Hi guys,

I notice after a while of driving, i feel a lot of heat around my legs & also my passenger complains about it. We do live in Malaysia & it is hot here(no aircon in car yet). Could it be the insulation that has gone over the years? What are your thoughts please.

Cheers
Cheers,
Mohan

W113 - 250SL
W126 - 280SE
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W212 - E250

Pawel66

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Re: Heat coming in thru the firewall
« Reply #1 on: August 03, 2021, 15:58:24 »
There is limited insulation in the leg room. I would check for:
- uncovered, unplugged holes (although not too many of them on passenger side)
- presence of exhaust heat shields

I never drove a Pagoda in a climate like Malian. On a hot day in my area it may feel a bit warm. But if any of the holes is open - much more hot air is coming in.

There are pieces of insulation under dash inside. You may look at SLS site to see what should be there and compare with what you have.
Pawel

280SL 1970 automatic 180G Silver
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Garry

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Re: Heat coming in thru the firewall
« Reply #2 on: August 04, 2021, 01:36:20 »
Also check underneath to see if you have the exhaust shields in place. Without them the floors will heat up lots.
Garry Marks
Melbourne/ Kyneton, Brisbane. Australia
1969 MB 280SL 5 speed RHD SOLD.
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Harry

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Re: Heat coming in thru the firewall
« Reply #3 on: August 04, 2021, 11:19:16 »
You'll be surprised at the amount of heat (and odors) that snake their way into the passenger compartment from penetrations in the firewall that are not tight.  This is especially true at speed.  Certainly check your firewall penetrations.
Harry Bailey
Knoxville, TN
1966 230SL
Automatic

StevenF

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Re: Heat coming in thru the firewall
« Reply #4 on: September 12, 2021, 03:37:35 »
I had a ton of heat coming into the car but so I replaced the firewall with a new pad and then installed a dynamat  style product
What a difference!
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StevenF

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1971 280sl
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Bamboo MB Tex

doitwright

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Re: Heat coming in thru the firewall
« Reply #6 on: September 17, 2021, 05:09:50 »
This may sound too obvious. Have you checked to be sure the heat is not coming from the heater core? The controls can be confusing for a new owner but the heating system does direct heat to the foot areas on the driver and  passenger side.
Frank Koronkiewicz
Willowbrook, Illinois

1970 280SL Originally Light Ivory - Now Anthracite Gray Metallic

Mohan58

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Re: Heat coming in thru the firewall
« Reply #7 on: September 18, 2021, 13:13:31 »
Thanks for the heads up. Will definitely look into this.
Cheer
Cheers,
Mohan

W113 - 250SL
W126 - 280SE
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W212 - E250

Norm

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Re: Heat coming in thru the firewall
« Reply #8 on: September 18, 2021, 17:13:51 »
You should probably also check your heater core valve.  Mine would not close properly and continued to allow hot coolant through the core resulting in the same problem you described.

There are two ways to check this.  An easy check is to adjust the heat to maximum, feel the heat coming in by the floor, then reduce the temperature lever to minimum and see if the temperature of the air coming in is reduced.  Another way is to block the input (I inserted a steel ball bearing in the inlet hose) or bypass the heat exchanger by connecting a section of hose from the input hose to the output hose in front of the firewall and then see if the heat entering the cabin stops.

If the heater core valve is the problem there is info in the Technical manual to check if it is installed correctly and / or replace it.  Replacement valves with the appropriate washers are readily available through several 113 part suppliers.

Good luck.

Norm
Norm
1966 230SL 162H Blue-Grey
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Mohan58

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Re: Heat coming in thru the firewall
« Reply #9 on: September 18, 2021, 23:20:09 »
Thanks Norm.
Cheers
Cheers,
Mohan

W113 - 250SL
W126 - 280SE
W126 - 300SE
W212 - E250