Heater hose return fitting replacement

[1991 Corvette ZR-1]

Hello all,

For those who have replaced the heater hose return fitting on the remote thermostat housing, did you leave the housing assembly bolted in place during replacement?

[1991 Corvette ZR-1]

Well the assembly looks fairly sturdy so it should be able to remain in place. Does anyone recall how many amps the fan relays are rated for? I picked up some spal fans to replace the factory fans and they are pretty beefy compared to the factory.

[secondchance]

If your question regarding fan relay amperage rating is because of concern over Spal fan, Spal fans will run with no issue with existing relays. I am running two Spal fans.
If anything, 120 amp alternator may be underpowered. I am running 200 amp rated Quality Power alternator. Quality Power high output alternator is newer generation Nippon Denso unit in custom CNC aluminum housing to work with CS144 mounting points.

[1991 Corvette ZR-1]

Originally Posted by secondchance

If your question regarding fan relay amperage rating is because of concern over Spal fan, Spal fans will run with no issue with existing relays. I am running two Spal fans.
If anything, 120 amp alternator may be underpowered. I am running 200 amp rated Quality Power alternator. Quality Power high output alternator is newer generation Nippon Denso unit in custom CNC aluminum housing to work with CS144 mounting points.

Good to know and I also have a 200 amp alternator fitted, so the electrical demands should be covered. Do you recall the connector route you went with the spals? Figured I would ask before I start cutting up wiring. The male connectors on these as is has PA6 marking but I can only seem to locate Delphi PA66.

[secondchance]

Spal fans I bought was from Dewitt and showed up with GM connectors. You might have to de-pin Spal connector, take a WAG, connect/run and see if the fan is running in correct direction.
200 amp alternator and Spal fans, good aluminum radiator and overheating will become a distant memory.

[1991 Corvette ZR-1]

Alrighty, I am open for to some suggestions? Appropriately sized EZ out? This happened while trying to remove the plastic retainer from the heater hose. What is left of the aluminum gave up before the plastic retainer did.

[A26B]

Try to remove the remaining bit still in the housing.
I have resolved problems like this by using a hacksaw blade to cut into the remaining band 2 or 3 places around. Then using a small chisel or center punch, drive the sections downwards & inwards away from the threads. If you cut into the female threads a little, no worries, just try not to go too deep with the hacksaw blade. Pipe threads are tapered, so you can chase the threads with a pipe tap just enough to clean them up. I suggest a couple of wraps with teflon tape on the new nipple.

[1991 Corvette ZR-1]

Well, team I have resolved the heater hose fitting issue. A 1/2-14 NPT tap finished off the material left stuck on the threads. So that problem is out of the way. One more problem has cropped up now and that is the fitting of the fan shroud to the Dewitts single row. Even the single row is a little beefier than the stock unit. The fan shroud fits inside the driver side against the end tank without too much issue. The passenger side is way off and may need some trimming. Wondering if others had to do this that went Dewitts.

If I do not do this, there is a noticeable gap from what I can see. Wondering if others had to trim the shroud. Pic attached.

[HAWAIIZR-1]

Originally Posted by 1991 Corvette ZR-1

Well, team I have resolved the heater hose fitting issue. A 1/2-14 NPT tap finished off the material left stuck on the threads. So that problem is out of the way. One more problem has cropped up now and that is the fitting of the fan shroud to the Dewitts single row. Even the single row is a little beefier than the stock unit. The fan shroud fits inside the driver side against the end tank without too much issue. The passenger side is way off and may need some trimming. Wondering if others had to do this that went Dewitts.

If I do not do this, there is a noticeable gap from what I can see. Wondering if others had to trim the shroud. Pic attached.

Glad to hear you made good progress with the hose fitting. You should have received an install kit so to speak with instructions with the radiator. They come with foam, spacer, and hardware. It is plug n play and a very nice fit and seal.

Having said that, last year I upgraded to spal fans, but I bought the whole Dewitt?s unit with housing to replace stock system as plug n play also. I?m not one to reengineer and like to keep it clean and simple. The spacers were able to be removed and not needed and the Dewitt?s housing for fans are real nice how it seals to the radiator and shroud. I removed the accumulator bracket that try to mod it to fit and held in place by other straps. Love it.

[1991 Corvette ZR-1]

Alright, Team I got this finally resolved and she is back on the road. The fan shroud does rest against the end tanks of the DeWitts radiator. The spacers worked as intended when the upper shroud was as placed over the radiator. Had to trim the cushions inside slightly. I would never expect anyone to follow in my footsteps on this procedure, but despite the amount of down time, I am happy with the results.

So here is a checklist for any owners brave enough to do their own heater hose nipple replacement in the future.

The old plastic retainers will be done for, you will need new ones for the press on fittings that connect to the housing. Jerrys replacement heater hose fitting comes with a retainer , however the other hose will need a replacement. You will need Dorman 800-407. It contains the retainer you need plus you end up with a spare heater hose fitting retainer.

There is a good chance your heater hose fitting will snap off close to flush with the housing. A special large size EZ out might do it but most likely will not. The pot metal will shred up before the corroded threads seized in the housing let go, that is what happened to me. I then used a 7/8 reamer drill bit to slowly eat away at the snapped off fitting. When I say slowly, hours of letting the bit eat a little into the fitting and visually checking the progress. Housing needs to be in a vice and be very careful not to clamp onto a section of the housing that compromises the bolts and connection containing the thermostat and seal.

Jerrys suggestion on the punch was spot on. It helped remove a good portion of material that could not be removed by the reamer because it was too far down in the housing. It takes a while though, pack your patience. You will need a thread tap 1/2-14 NPT to chase the housing threads and knock out any remaining material lodged in the threads you cannot reach with a punch. Go slow and take the tap out often to visually check threads are being cleaned off.

The fans I used are 12 inch spals. You can get them from summit part number SPU-IX-30103202.

https://www.summitracing.com/parts/s...SABEgLmiPD_BwE


About $500 for two including tax. They will need to be trimmed to fit. The passenger side will require a significant amount of trimming, including removal of one of the support fins to clear the accumulator and its bracket. The fan side closest to the thermostat housing will need to some clearance to fit around the housing. Yes, these fans are huge. Together they both move about 3800 cfm of air and I believe it, even with the curved blades they are loud. They are not on for very long either.

Overall, I would recommend just getting the DeWitts shroud for about the same amount of money as it is direct fit. If you like trimming and custom brackets, the extra 1000 worth of cfm the summit spals flow over the DeWitts drop in unit is a nice reward. You do not need it, but it was fun to make them fit. I ended up needing to re-pin the connector off the spals to new 12 gauge plugs to fit the factory female plugs. These work:

https://www.racetronix.biz/p/connect...-2f-2m/rcs-011

The Summit Spal wiring will need to be swapped to match the factory wiring flow for positive to ground, otherwise the spals will push air instead of pulling as intended. Red wire off the spall needs to connect to the black w red tracer wire on the factory connections.



TLDR; Take your thermostat housing to a machine shop for R&R