Which thermoguard is correct for 78 magnum

[Tony Tee]

the top one with the black cap plug has been trimmed to fit a different style battery.
The lower one has been trimmed at the top right corner to clear the battery terminal. Aside from being trimmed, which one is correct for a 78 dodge magnum? Thanks in advance, Tony

 

[XS22J8R]

I can't guarantee my '78's thermoguard was the one it was born with, as I've only owned the car 3 years. But it probably is. It appears to be the lower one in your pictures.

 

[Tony Tee]

I can't guarantee my '78's thermoguard was the one it was born with, as I've only owned the car 3 years. But it probably is. It appears to be the lower one in your pictures.

View attachment 1768945

Thanks for the pic. I wonder what happens when the pump dies? Drill a hole to access the nut and afterwards find a cap to re-seal it? Or back In the day, replace the whole thermguard with a new one. ? Just wondering.........Nice engine compartment!

 

[WileE]

Thanks for the pic. I wonder what happens when the pump dies? Drill a hole to access the nut and afterwards find a cap to re-seal it? Or back In the day, replace the whole thermguard with a new one. ? Just wondering.........Nice engine compartment!

The pump has a seal. I recently replaced the thermoguard in my Cordoba, along with a new pump. It's a simple task. Mine is like the one in the red engine compartment.

 

[Vaanth]

The battery heat shield, Thermo-Guard, was combined with the windshield washer reservoir for B-bodies for 1978. Part number 3799269, marked "ASSY NO. 3799267", was used up to 4-10-1978. Part number 3799494, marked "ASSY NO. 3799485 W/SENSOR NO. 3799486" was used after 4-10-1978 and continued through 1981 on the R-bodies.



When assembled, the pump was installed first, and the upper part of the Thermo-Guard was glued to the bottom part. To replace the pump, if the reservoir had a sensor, the sensor is removed and the pump removed through the hole. If no sensor is installed the cut-out where it would be mounted is removed, and the pump removed through the hole. A black Caplug is installed in the cut out hole after the new pump is installed.

The following image is from the 1978 Service Highlights:

In the following image, the four Thermo-Guards include:
- upper left: 3799269
- upper right: 3799494 that has had the pump replaced
- lower left and right: 3799494 with fluid level sensor

One difference between 3799269 and 3799494, in addition to the different markings, is the addition of two plastic posts, as a pump installation aid, which prevents the pump from turning as the "nut"/screen is tightened in the reservoir.


Another difference between 3799269 and 3799494 is the cutout for the battery vent caps was opened with the switch from individual battery cell caps to the multi-cell snap-in caps.


The prior B-body Thermo-Guard was part number 4005059 which was just the battery heat shield only without the combined washer reservoir:

 

[Tony Tee]

The battery heat shield, Thermo-Guard, was combined with the windshield washer reservoir for B-bodies for 1978. Part number 3799269, marked "ASSY NO. 3799267", was used up to 4-10-1978. Part number 3799494, marked "ASSY NO. 3799485 W/SENSOR NO. 3799486" was used after 4-10-1978 and continued through 1981 on the R-bodies.
View attachment 1777537
View attachment 1777544

When assembled, the pump was installed first, and the upper part of the Thermo-Guard was glued to the bottom part. To replace the pump, if the reservoir had a sensor, the sensor is removed and the pump removed through the hole. If no sensor is installed the cut-out where it would be mounted is removed, and the pump removed through the hole. A black Caplug is installed in the cut out hole after the new pump is installed.

The following image is from the 1978 Service Highlights:
View attachment 1777535

In the following image, the four Thermo-Guards include:
- upper left: 3799269
- upper right: 3799494 that has had the pump replaced
- lower left and right: 3799494 with fluid level sensor
View attachment 1777539

One difference between 3799269 and 3799494, in addition to the different markings, is the addition of two plastic posts, as a pump installation aid, which prevents the pump from turning as the "nut"/screen is tightened in the reservoir.
View attachment 1777536

Another difference between 3799269 and 3799494 is the cutout for the battery vent caps was opened with the switch from individual battery cell caps to the multi-cell snap-in caps.
View attachment 1777560

The prior B-body Thermo-Guard was part number 4005059 with was just the battery heat shield only without the combined washer reservoir:
View attachment 1777540

Thanks! Great info!

 

[RR Fan Dan]

Okay, i’m going to ask a stupid question. Why does the battery need a heat shield? i’m not familiar with these later cars.

 

[RemCharger]

Okay, i’m going to ask a stupid question. Why does the battery need a heat shield? i’m not familiar with these later cars.

So it doesn't get hot.

 

[RR Fan Dan]

So it doesn't get hot.

i get that, hence the name, but what makes that car different than the other 99.99% of cars that don’t have one. What causes the battery to get hot?

 

[WileE]

i get that, hence the name, but what makes that car different than the other 99.99% of cars that don’t have one. What causes the battery to get hot?

Typically it's the ambient temperature of the engine compartment and quick charging or discharging, heavy load from the vehicle's accessories especially in hot weather or climate.

 

[Vaanth]

Like lower temperatures, higher temperatures can affect battery performance. Higher temperatures can lead to overheating of the battery electrolyte, causing degradation and shortening battery life. Elevated engine heat for emissions reduction and further increasing heat due to added loads of emissions systems and electrical loads were causing even higher underhood temperatures.

The Thermo-Guard battery heat shield was introduced on 1975 B-bodies and C-bodies to address higher underhood temperatures. This Thermo-Guard is a molded polypropylene form fitting shield with a molded urethane insulator facing the engine to shield against heat. It is formed with an opening facing the radiator yoke (core support) to allow cooler grille air to enter the Thermo-Guard further cooling the battery. Chrysler tests showed up to a 37 degree Fahrenheit reduction in battery temperature using the Thermo-Guard.

In 1978, the B-body Thermo-Guard was combined with the windshield washer reservoir as shown in the foregoing post to reduce underhood space use of the separate reservoir, and the reservoir with fluid added to the heat shielding for the battery.

Modern vehicles often employ a battery thermal shield for underhood batteries. Ram trucks have a thermal fabric based, formed wrap for the battery, and Chrysler still uses the Thermo-Guard naming, though the spelling has changed to Thermoguard.

.

 

[RR Fan Dan]

Elevated engine heat for emissions reduction and further increasing heat due to added loads of emissions systems and electrical loads were causing even higher underhood temperatures.

Well there you have it, our government working hard for us. Try to fix an imaginary problem and create bigger problems as a resiult.

Thanks for the explanation. I’ll be more mindful looking under the hoods and at batteries of newer cars. i honestly have never seen one before and i have owned lots of vehicles in my lifetime.

 

[LS-300]

Well there you have it, our government working hard for us. Try to fix an imaginary problem and create bigger problems as a resiult.

Thanks for the explanation. I’ll be more mindful looking under the hoods and at batteries of newer cars. i honestly have never seen one before and i have owned lots of vehicles in my lifetime.

This was Chrysler engineers not the Government. If the Government was involved that all automotive manufactures would be required to have them.

 

[RR Fan Dan]

This was Chrysler engineers not the Government

You misunderstood the gist of the comment. If it were not for the government imposing emission standards on the car industry, then temperatures would not have risen in the engine compartments. To meet new emissions standards, Chrysler engineers had to develop lean burn engines that ran hotter to meet the new standards. This caused batteries to overheat, Chrysler engineers developed thermo-gaurd battery covers to correct the issue the government caused in the first place. Hence the government working hard for us.