Hello,

I blew an oil cooler and can’t find anything on what a good replacement would be. I would like to keep the original placement if I can, but I will relocate it if I need to. What do y’all recommend for a replacement? It’s for a 90 GTU with a half-bridge port.

 

I purchased a new oil cooler for my 1988 GXL, the original one was quite bent but did not leak. I did not use a backer wrench when I tried to loosen the oil line at the front cover, twisted the metal line so I ordered new SS oil lines from one of the well known RX-7 parts supplier.



The mounts were never removed and after 35 years the bolts just snapped, I was lucky to find a pair on eBay. A bit of clean up and some primer and paint and I am back in business! By the way, Is the mount attached correctly in the pic?

I just tried to attach the new oil lines to the new cooler, the threads on the lines measure 17.9 mm, the plug bolts on the cooler measure only 17.2 mm. That's way too small.

I am going to get an 18MM tap to enlarge the holes on the cooler. This is the second part that needed to be modified. I bought a replacement A/C condenser also made in China that one of the connections was the wrong size, I had to have the proper size welded onto it!

I do not think I will source anymore parts made in China unless I have no other choice. This is what I get for buying the cheaper parts!

 

just a little unsolicited advice ... why don't you try to find a fitting/adapter (Earl's, Vibrant, Holley, Russel, etc.) to use the original hole instead of drilling and tapping with the risk of metal shavings getting into the cooler.

 

The problem of metal shavings getting into the cooler occurred to me right away.

I will insert a piece of oiled white cloth into the cooler to catch the shavings, then carefully pull it out of the hole with the hole in a vertical orientation.

Where do you find an adapter from 17mm to 18mm?

 

i wasn't saying adapt the 17 to 18, i was more thinking if you could find something to adapt 17 to -10 AN. you mentioned buying lines from a well-known Rx-7 parts supplier so i assumed they were -10 AN lines.

that said, i just searched for a few minutes (hoping to provide a link) and nothing seems to be readily available, so you may have to go with your original idea after all.

 

I would look up the specs on the new cooler. I bet they are a Standard and not metric. I'd do what diabolical1 suggested and ger the conversion bungs. That new cooler does not have an internal thermostat like the factory one. You need to add and external oil cooler bypass thermostat like and Earl's or Motec. This would also mean you will need to alter those new lines to put the tstat in. I like making my own lines out of nylon braided -10AN lines. If you go this route, don't get cheap -10AN fittings.

 

i didn't occur to me, but you're probably spot on.

 

I really do not know what size a -10 AN fitting is, going to find out though. This forum is great for learning about mechanics and other things!

The replacement oil lines were made for the RX-7, so the ends should be the same as the stock fittings.

I compared the fittings on the new lines to the stock ones, and they are a match in both size and thread pitch. So, once I re-tap the holes in the oil cooler I will be able to install it without any other problems (Yeah, right!).

 

The following is my attempt to re-tap my new oil cooler to fit the oil cooler lines I ordered.

The problem is that the fittings on this cooler are too small ! 17.2mm verses 17.9mm hose size!

To fix this mis-match I ordered a 18mm x 1.5 tap.

Here is my re-taping of the 17.2mm threaded holes on the cooler.



Here I put some tape into the cavity to prevent any metal shavings from getting into the cooler.



I measured the oil line fitting depth and used tape to make how deep the re-tapping had to be.



Make sure when you start the tap that you are square to the existing hole!



These are the shavings removed from the bore, I used a Q-tip covered with oil to remove any shavings after taking oil the oil covered cloth that I inserted into the bore.



The oil cooler lines fit very easily when I finished re-tapping the bores!

I am going to install the aluminum crush washers supplied with the lines.
Cost of the 18x1.5mm tap was $14.99

 

You could experience a longer warmup time and lower oil pressure while the oil is thick while cold without an oil thermostat.

 

-N numbers are in 1/16". -10 would be 10/16", which reduced is 5/8". -4 is 1/4", -8 is 1/2", etc.

The next time you tap something you don't want chips to get in, coat the tap with grease, the chips stick in the grease and it helps lube the tap.

 

I do not think the flow through the oil cooler would work at all without the bypass valve installed!

It opens the ports to allow the oil into the cooler at 150 degrees.

Below 150 degrees the oil flows only between the oil lines on that side of the cooler.

When I installed the bypass valve I put the large spring where I thought it fit, looked okay to me!

Then I remembered I took a photo when I took it out to re-tap the holes for the lines.



The large spring fits very nicely over the end where the small spring is, oops!

Glad I caught it, I would of bet good money I did it correctly.