View Single Post
tduncan001 tduncan001 is offline
Registered User
 
tduncan001's Avatar
 
Join Date: Oct 2010
Location: Twin Cities, MN
Posts: 34
914/4 Easy heat exchanger fix

For minor repairs only - my HEs are solid almost all the way around but there was some deterioration at the ends where the HE joins the exhaust tube causing "some" of my warm air to escape outside rather than into the car. I also had a slight exhaust smell in the car due to the less than perfect integrity of the seals. There is not that much pressure within the HE space so this fix works. I do not think it would last for an exhaust repair as there is a lot more pressure.

Having purchased a set of stainless steel heat exchangers that I do not want to install until I fix the small oil leak on the right side (looks like it is coming from the push rod tube seals and maybe a tad from the valve cover), I came up with an easy, inexpensive and successful solution - I will call this an A+ half-ass repair job until I can do it right. Weird how only the right side has an oil leak.

Materials:1)
One silicon cutting mat (I took one from my wife). This material has high heat resistance, is easy to form and stays flexible. $10
2) One roll aluminum foil tape (the stuff you would use to fix a hole on a water heater flue). $3
3) Hose clamps (buy the 100% stainless steel ones). $12

Process
1) Take a wire brush and get as much of the rust off the metal as possible.
2) If there is oil on the area, use brake cleaner to get it off.
3) Take small pieces of the aluminum tape and apply in overlaying patches to cover any small gaps. This stuff has very aggressive adhesive so working with small pieces is the key. This stuff sticks to rusty metal!
4) Turn on your rear heater blower fan (car does not need to be running) and inspect the repaired area for any air leaks (use your hand and feel for air). If you have some, go back and put more tape on. After there is no leaks, apply several more layers of aluminum tape to build up the thickness (might as well do the half-ass repair right).
5) Optional - As an added measure for structural integrity and longevity, cut a piece of the silicon mat into a strip maybe 3 inches wide and 12 inches long. Stretch this over the repaired area tight and secure with a hose clamp. I did this for each area where the pipe and HE join (total of 4 in back). I figured this would help secure the repair and because the silicon is flexible, it would provide some cushion and allow minor movement of the repair without breaking the seal.

Result
I now have hot air (no oil/exhaust smell) blowing into my cabin at a strong flow within 2 minutes of starting the car. I live in MN and drove the car in our first blizzard as a test. Had to do it. No gloves and my windows were fog free.

One side note, I have read many articles where it says the the heat is either defrost or floor. That is not true - you can slide your heat lever to the middle and have heat diverted to both defrost and floor at the same time. I keep mine about 60% floor and 40% defrost.

I did purchase new heater blower hoses from Pelican and all of my other hoses (the ones connecting to the flapper boxes) were in good shape.

Hope this helps any chilly 914 drivers.
__________________
1971 914/4 1.7L all OEM
MB 2005 SL55 AMG
2008 Acura MDX
Past
Too many to list
Old 11-16-2010, 05:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)