Friday, May 13, 2011

Rebuilding the Lotus Esprit S1 Radiator Assembly

The S1 Lotus Esprit has a prominent radiator shroud (a huge piece of molded fiberglass which bolts underneath the front of the car and holds the radiator in place). Since the outer face is visible from underneath the car, it was important to get everything back to factory spec. Mine was in bad shape and broken in several places. Since the radiator was not properly secured (all of the fixing bolts had worked themselves free over time), the heavy radiator was jumping around inside the shroud which broke the fiberglass in several areas. I re-glassed the bits together and then added a few more layers to ensure the new assembly was stout. The process took a long time, mostly because the fiberglass cloth had to be cut in the right pattern in order to create a uniform pattern on the backside of the shroud assembly.

From there, I sent out my radiator to get rebuilt and then welded a new metal radiator surround thanks to a kit supplied by SJ Sportscars. The old radiator fans (antiquated by today’s standards) were replaced with more reliable 7 x 2 inch fans. I needed to fabricate mounts for the fans to bolt directly to the radiator, but it was pretty easy to figure out.

As the last step, I refinished the exterior of the fiberglass shroud assembly, fixing some curb rash and rock damage on the lower edges, as well as smoothing out the seams and pinholes that were left over by a shoddy build process at the Lotus factory. After fitting a new metal grille, mounting hardware and a strip of sealing foam, I bolted the radiator back in place. Now it's ready to mount back to the car.

Working on the fiberglass radiator shroud after having
re-glassed the entire structure.

The shroud after the color was applied.

One of the aftermarket radiator fans.

The radiator fans attached to the radiator assembly.

A side view of the radiator shroud, which was re-inforced
with three full layers of new fiberglass.

A new radiator shroud grille, which I had powder coated
in wrinkle black.

Job done!


  1. What a fantastic job your doing, Congratulations and good luck on the finished product. Can you let me know the Chassis number for my S1 register. I'm sure your documented work would be of great use to the many enthusiasts in the world.
    Many thanks

  2. Hello Steven,

    Thank you for the note. Where exactly is the Chassis number stamped? I feel a little stupid not knowing this given how far deep I am into the project. I've done research online and found a list of chassis numbers that correspond to all S1 Esprits, yet none of the numbers stamped on my car seem to match any of those. Let me know and I'll gladly send you the info.

  3. Hi Renn,
    There should be a plate under the (Front) bonnet above the passenger foot well. Here is a pic of the plate on James bond's S1 (TSWLM)

    Or the number should be on your log book.

    The number should be something like 7702 0244G
    77 being the year, 02 being the month 0244 the car number & G being the country destination.

    If you don't have the number let me know the engine number & i'll find out more information for you.

    If you dont's have the chassis plate for your car don't worry I can get one for you.

    Cheers Steve
    Keep up the good work. (I'm jealous of your ability)

  4. Hi Renn - great work and love how the cars coming together. Do you think you could fit 4 fans if you spaced them closer together? Any chance you could post where you got the fans from as I would like to get some. Gavin, S1 #165H

  5. Hi

    Fantastic Job

    I am also restoring an s1 right now. We are at about the same point in the restoration.
    Only thing I have seen which may cause an issue is the radiator fans. I tries fitting them there too, behind the radiator. You may find that there is not enough room for them there, and the gap between the radiator and the anti roll bar is less than an inch.

    I had to fit them in front of the radiator.

    I can show you some photos if you like



  6. Mine is number 127G



  7. Hello Renn, did you have any clearance issues with the fans? Doing my fans right now. Thanks Gavin, S1 165H