Air Conditioning/Engine Heat in Cabin

[fhwlloyd]

I have a 1969 series II FHC since 2012. I love the car and it is generally in great condition.

The only issue I have is the engine heat. The air through the vents into the cabin is always warm. Even when I've been driving on cold evenings I need to open the windows slightly occasionally to moderate the temperature. I can't conceive why a heater was ever fitted as the engine seems to do enough by itself.

I see on many restorations a lot of heat insulation is laid but are there any other tips/pointers to try and reduce cabin heat? Is this a universal problem or may I have an issue that needs fixing? Should the air through the vents be cool? I've always assumed it's just because the duct runs through the engine bay.

Thank you in advance.

[mgcjag]

Hi.....are you sure you heater valve is actually turning fully off........however yes there is a lot of heat from the engine....Steve

[1954Etype]

Make sure you have blanked off all the holes in the bulkhead. Also, the seal between the gearbox tunnel cover and body is crucial. It will let in huge amounts of heat if it isn't sealed. Make sure you have the heat defelctors fitted under the car. There is a lot you can do to help reduce heat.

[Bfastr]

I second what Angus says, look around the openings where the AC hoses come into the cabin, pack them with something, anything to block heat. and then make sure this front deflector is there, mine was missing and after putting one back on it made a big difference. The exhaust is off in this photo, but you can get the front deflector in there if the pipes are on. with some patience and maneuvering.

Bob

[fhwlloyd]

Thank you for the feedback. I checked and the heating valve is at least shutting off.

[MikeMilton]

In addition to the great advice above, there are some other products you might consider. (I have no financial interest in these products)

We will be using Lizardskin http://m.lizardskin.com/car-ceramic-insulation.html in the footwells in a bare-metal restoration that is currently underway. We are also ceramic coating the headers (inside and out) and the first section of pipe.

Also, ZircoFlex form might be a better choice than other sheeting for heat shielding. In addition to using it where there are (or should be) shields presently, it might make sense to also shield the heater box and/or the cold air feed.

[alfred]

I've had the same heat issues with my 68. Two things that have helped me:

I added a shut off valve on the right side of the engine near the firewall so no hot coolant can run through the dash and heater box.

My connection between the air vent on the bonnet and the intake on the heater box did not seal so I added a thicker rubber seal on top of the heater box.

With those two changes I now have air the same temp and the outside environment coming through my vents.

Still a lot of heat comes from the firewall and transmission tunnel on a hot summer day.

[PeterCrespin]

Correct on the air duct seal, which people often don’t check. Less so for the added valve, but only because a correctly functioning heater valve isolates the heater matrix too. Isolating it twice ‘ought’ to be redundant, since coolant flow is needed to shed heat. Granted, many valves may not totally shut off.

For console heat moderation, the big squishy sponge is essential to have all round the top half of the gearbox.

[CoolCat]

If you have all the bottom shields fitted in the engine compartment, the transmission tunnel becomes a primary path for hot air exiting the engine bay. As fitted from the factory, there's a large wad of foam rubber on top of the transmission. It cuts down noise, but also cuts down on heat by restricting airflow through the tunnel.

Instead of commercial heat insulation or padding, I use ceramic paper under the carpet. The paper is sold at industrial supply stores, and is generally used for boilers and kilns. It's 1/8" thick and can be glued right to the floor with 3M adhesive. You need to be careful about building up the carpet under the center console, or you'll have difficulty fitting the speaker enclosure.

[docdcc]

All great suggestions . The only other thing I did was put a gm fan in the heater box which runs at high rpm and has different fan blade curves. This moves massive amounts of air through the cabin. Double check that hot water is not going through heater box.
docdcc

[CoolCat]

Good point about hot water going through the heater box...the valve isn't always effective. The air flap inside the heater box also has a seal which is worth replacing.