Radiator Inquiry: Replacement Brand Recommendation? and, Single Pass Procedure?

Ahoy !
Assistance, please with two radiator inquires, driver cars, not racers, not show cars.

  1. 1990 XJ-S 12 cyl. Recommendations for replacement radiator, “bolt-in” or, as close as possible considering we are talking XJ-S ?

  2. 1992 XJ-S 12 cyl.
    a) Can someone please point me to the procedure for doing the Single pass conversion ?
    b) Recommendation for a replacement radiator ?

Thank you.

Richard Cielec
Greater Chicago Metro U.S.A.
ps: A joyous and profound Independence Day to All.


The cars have left and right header tanks, stock the left header tank is divided about a third of the way down from the top so all the fluid from the left head flows across the top third of the core from left to right where it mixes with the right side fluid and both flow back to the left lower header tank where the single return hose goes to the water pump.
The modified kits have the left and right header tanks but the flow out of the left head goes to a cross pipe that “T”ed into the right side just behind the single upper right inlet. All the fluid flows across to the left header tank that has a single lower outlet for the return hose. A kit was offered by a place in Texas but many owners had issues with them, I got mine used off this site 10 years ago so never really delt with them.
My first jag 71 V12 2+2 had heating issues that took me a while to solve. But one of my first attempts was a bigger radiator by Griffen Radiators it was a perfect fit and excellent quality. The E Type 12’s had header tanks top and bottom, so each upper corner had an inlet from the head and the fluid flowed down to the center outlet. I think that was a better design, of course that did not solve my problem and I tried everything to keep it from overheating, the very last thing I learned was that the thermostats must be “double action” for these engines and not one Jaguar parts shop ever knew that! The fourth set I bought was the right kind and that car has never even started to run hot since then.
I think Griffen will make a radiator for your XJS, your biggest decision is to make your own mod, but I think a big core Griffen with a stronger aux fan and a good/new fan clutch will serve you well. Stop and go traffic the problem is air flow, good fans will fix that.
In very hot Georgia
Have a Great 4th and Fly Navy!


In my 1989 V-12 I just installed a Wizard Cooling aluminum radiator. Very pleased, fit and finish were of very high quality. Drop in replacement for the original.

Had the proper connections for the transmission cooler. In the left header tank below the divider plate (ie cool outflow region) they had welded a M22 x 1.5 bung for the aux cooling fan temp switch, which I didn’t need as it was installed in the water pump housing. I installed a brass plug and was thinking for potential future use.

No affiliation, just a pleased customer. I actually visited their shop just outside Buffalo NY, as I decided to do some modifications for a dual electric fan setup. They gave me the grand tour and all I can say is very professional well outfitted shop.

Paul Stoneman
1989 XJ-S V-12

Hello, Mr. Stoneman.
Thank you for the reply.
Your description sounds like you did not install a single pass but the original configuration (pass and a half? half passed ? whatever the descriptor is?).
All the best,
Richard Cielec
Greater Chicago Metro, U.S.A.

Hello, Everyone.
Thank you for the on and off list replies. Your advice and support are sincerely appreciated. And, thank you, also, for realising I am not trying to free-load but, to learn so I, too, can “pass it forward”.
Best Regards,
Richard Cielec
Greater Chicago Metro, U.S.A.

Hello, All.
Here’s is what I’ve learned from the replies received both On/Off list. Feel free to comment and adjust my thinking.

  1. Be Cool, Wizard, Griffen are each excellent choices for single pass radiators. But make certain single pass is the configuration being discussed.
  2. Ask about / have installed a drain plug or spigot.
  3. Ask about/ have installed a tap for the Auxiliary Fan Temperature sensor
  4. Ask if they supply the needed hoses and piping for the Single Pass conversion.
  5. Ask about the automatic transmission lines connexion points - WHAT SHOULD I ASK ? A) IF THEY ARE THERE? B) THREAD DIMENSIONS ? C) OTHER ?
  6. Ask if they provide mounting bosses for Auxilliary Fans mounting.
  7. Anything else I need to ask them ? (If I get a compleat check list maybe it can be placed on the Jag-lovers site as an Aid to those desiring a radiator replacement. Nit-picking through years of postings is nuts. Thoughts ?)
    Thank you.
    Richard Cielec
    Greater Chicago Metro, U.S.A.

Oops !
6A. Ask about cross-over LH to RH piping to configure the flow for Single Pass.

Richard Cielec
Greater Chicago Metro, U.S.A.

Something to think about: In OEM configuration, the radiator is electrically isolated from the car – mounted in rubber bushings and connected using rubber hoses. This might be important in preventing electrolytic corrosion between the aluminum block and the brass radiator. Going with an aluminum radiator might avoid that issue. Whatever, if you find it’s convenient to electrically isolate your new rad, it probably couldn’t hurt anything.

In 2014 when I started the engine bay restoration of my wife’s 1990 XJ-S convertible (5.3L V12 with Marelli ignition) I did a lot of research on a replacement radiator because the inside of the original one was badly clogged contributing to higher coolant temperatures. Much to my surprise at the time the best deal I found at the time was an OEM radiator (MHE4190BA) from the local Jaguar dealership for $752.92 plus taxes. Of course it fit perfectly and the coolant temperatures have been much lower.



Yes, it is the original configuration.

It came with a drain spigot. Although I find I don’t use it anymore. I use a marine oil change vacuum oil extractor to pull all the coolant out through the right side tank after removing the banjo bolt. Much cleaner and neater.


Yes, but does it get the crud out? Or does it just remove the liquid and leave the crud in there?

You raise a good point.

The inside diameter of the suction hose is about 1/4", when first inserted the bottom of the tank feels kind of squishy, ie crud. After sucking the everything out the bottom “feels” cleaner, ie no more squishy feeling. Can’t do anything for the outlet tank as it’s blocked by the divider plate in the left header (from above). I start with the left side inlet tank, then move to the right side “mixing tank” after I can’t get any more out.

Having said that, I’m not sure either the drain petcock or the disconnecting the lower rad hose would remove much crud either. As both are several inches above the bottom of the their respective header tanks.


Shame on Jaguar for not providing a functional coolant drain. Yes, disconnecting the lower rad hose accomplishes nothing, not only because it’s several inches up from the bottom but also because it’s on the downstream side of the core – the crud has already plugged up the tubes, never gets that far. And the cute little petcock on the cars that did have a drain pretty much prevented any serious removal of crud.

All why I replaced my petcock with a hose barb, connected a short length of hose, routed it out the bottom of the car, and plugged it there with a plug in the end of the hose. Easier to drain – just remove the plug – and serves as a “dirt leg” to collect crud while you’re driving. Still, the passage through the hose barb wasn’t as large as I’d like; to do it right would involve taking the rad out and brazing in a much larger port there.

BTW, that hose barb was an impossibility, some oddball thread, probably BSPP or some such. Had to drill out the original petcock and braze a hose barb to it.

Why do you want to do that?

Thank you for the interest.
Radiator needs replacement. I am deferring to the common wisdom among contributors of this forum to replace with a single-pass configuration.
Richard Cielec
Greater Chicago Metro, U.S.A.

Not sure if it is the “common wisdom” among contributors (smile) There are certainly those who believe the dual pass radiator should be scrapped and replaced with a single pass unit.

There are also those (including myself) who believe the dual single pass radiator is fine and all the cooling system needs is proper maintenance.

This topic has been discussed at great length over the years, to the point where I added a link to my website detailing my thoughts on keeping the dual pass radiator.

If interested you can access the website link at




I agree with Bernard, a well maintained stock system will do. In my post I did go with the single pass change because I got a used complete kit cheap, and since my car was getting a new water pump is why I did that. I do describe how the mod kit works. Bernard’s plans for a down flow mod would really have been the way to go, to bad that Faster Jag’s did not fab that style up. That Wizard Rad looks good and an easy drop in, I think a clean rad and stronger aux fan is our best set up.
if you really want a cross flow you are going to have it fab-ed up so copy Bernard’s if you are going through that much effort.
if you want to go with a cross flow I can send a few photos.

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The OEM 1-1/2 pass configuration will work fine when kept in tip-top working order. The primary reason to convert to a single pass configuration lies in what happens when it’s not in tip-top working order. With the OEM 1-1/2 pass setup, the upper 1/3 of the radiator can get plugged up and cause valve seats to start rattling in the B bank while the A bank is running fine and the temp gauge is indicating all is well. With a single-pass setup, it takes more crud to stop up the radiator to the point of trouble (if you opt for an aluminum radiator it’s all but impossible), and when it gets stopped up the symptoms are as you’d expect, creeping higher temps on the gauge.

Unfortunately, converting to the single pass requires a suitable radiator and a bit of plumbing to get the flow from both thermostat housings to the same side and teed together. Not a lot of room in the XJ-S engine compartment for such shenanigans.

John’s Cars offers a great radiator for use with big block Chevy engines, designed to fit the XJ-S. Unfortunately, if you mention you’ll be using it with the Jaguar V12 engine, they’ll refuse to sell it to you. That’s the kind of shop they are. So, most have opted for a custom aluminum rad. Supposedly some Mustang or other Ford radiators will fit pretty well, though.

The stock V12 radiator works perfectly well in the hottest of conditions in my experience in Florida where I have been daily driving an 89 XJS.
It is recommended that if you don’t know the condition of the radiator have it rodded. After which, braze in a drain plug as I have done and many others on this forum.

http://www.georgiajag.com/Documents/BeCool%20Radiator/Be%20Cool.html This might help. I did this on my car and ran nice and cool although it really did not have much trouble beforehand.