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XK Cooling #2

XK- Cooling #2

Hello to all, Now that warm weather has finally arrived in Chicago, I am reminded that last summer I vowed I would do something to curb the overheating in my 150 fhc. The temperature is fine as long as the car is moving, but if I get into any stop and go traffic, the temp gauge starts to rise. I have the radiator boiled out at a radiator shop but it didn't help much. What should I do next? An auxiliary electric fan? If so, who has them? - Don Sime

Don, How hot is hot? The car is fine in the 200F range. Make sure you are running 50% coolant and a 7lb cap (use the correct depth cap for your filler neck-VERY CRITICAL!). If you can find propolyene glycol coolant, use it. Available at most racing shops. I have aux electric fans. Various capacities. - George Badger

I think a local shop here in the Seattle area has successfully retrofitted waterpumps from the later 4..2 engine to eliminate this problem. - William C. Burke

The late 4.2L waterpump can easily be retrofitted into any earlier XK engine. Take$ - George Badger

A common problem, Don -

The real cure is to move North! Second (very close) is to hustle down to State & Archer, in Chi-town and pick up a large auliliary electric fan from J.C. Whitney / Warshawsky & Co. Ensure that it's 12 volt, install it on the front of the radiator (unless you can verfy that it won't interfere with the main fan if mounted on the rear) with through-the-radiator fasteners (carefully, so as not to harm the radiator) and, during installation, ensure that it blows air through the radiator. Connect it to a separate switch carefully mounted under the dash panel (so as not to call undue attention to it), and try to run a separate fused line from the switched side of the ignition switch to the fan, and from the fan to battery ground (this way, you don't forget and let the fan run the battery down!). Don't connect it to the other switch that controls your starting carburetor; though it looks the same as those used for fan control on the later crs, the closure temperature is different, and it won't work as needed.

Best of luck with this effort! Of course, and good auto shop (Pep Boys, Penn Jersey, even U-Haul (they supply them as part of a towing cooling system upgrade package) can also supply you with the fan. A 'better' solution ould be a newly-fabricated radiator with more cooling tubes and fins (thicker - 4-row), but expenses mount up fast - not a bad solution for a daily driver, though; poor for a concours d'elegance competitor, though. - Larry Schear Twin Cam, Inc.

Me Too. I am moving my XK120 to Florida this summer and also would like specific info as to what kind of electric fan to install?? Is it worthwhile to completely remove the mechanical fan and just use an electric one?? Second question: Is there an overdrive unit that can be retrofitted?? Sure would be nice to cruise at a lower RPM. - Steve McDonald

Steve, The answers to your questions are YES and YES. I have various electric fans per your requirement and OD is available but I doubt the expense is worth the trouble. Your call. - George Badger

Don, Some further info to hopefully help with your overheating problem.

Have you checked your thermostat. This should open at 72 degrees. Coventry Auto Components sell the correct original bellows type part TC2 at just £6. They also sell an auxillary Kenlowe fan system for the XK. This is priced at around £85 plus VAT and can be set to correspond to different temperatures / times of the year. CAC can be contacted on:

Tel: 01203 471217 Fax: 01203 421123

- Dave Roche

Don, With respect to your overheating problems, have you checked the usual carb settings, timing, leaks and radiator condition. Even with all the above OK, standing in traffic with the XK's small radiator aperture, will cause the temperature to rise, but moving should return the temperature to normal.

By far the best aux fan I have seen used is the Kenlowe fan. These are available for the XK at Guy Broads in the UK at around £110.

For further info, send an email via the web site at: - Dave Roche

Be sure to check that you have a by-pass thermostat. This is available from XK's Unlimited. This thermostat type ensures that all of the coolant goes into the radiator for cooling. - L. Eggers

A short-cut for making an electrical connection for an occasional-use auxiliary fan (on my no-turn-signal 120 OTS) was to put bullet ends on the fan wires plugging one into the extra side light hole and the other into the extra"ground" hole at the 10-way connector on the left side in front of the radiator.

The fan now operates when I turn on the side lights. It is neat, and easy to disconnect whenever I want to take it off. Just label the wires after you've figured out which way pushes air through the radiator, not back in your face.

XKs with turn signals don't have the same spare connectors but it's a simple matter to add a double connector to the side light hot wire (above or below the 5/10-way plug) and attach your fan wire there. There are several options for the ground wire either in the 5/10-way connector or directly to the body.

It surely saves time and the trouble of adding another switch. The only down-side is that your fan will run whenever the side lights are on, day or night. I did not put a larger fuse in the circuit but after several years of use there's been no problem.

"Water-wetter" products will also help as they increase the heat-transfer efficiency of the coolant but they may also increase the possibility of leaks. I have experienced near a full 10 deg. C lower operating temperature using water-wetter in my 120s. - Dick Cavicke 120 OTS & FHC

A very 'elegant' solution, Dick. Thanks for the idea(s)! - Larry Schear Twin Cam, Inc.

On this subject, I would like to know if there is an easily removeable electric fan for an XK120. It would be nice to be able to drive to a car show in warm weather using the electric fan as auxiliary cooling and then remove it once you are parked on the lawn and people are gawking at your finely restored engine. - Carl Hanson 1951 XK120 FHC

Don, 1. Make sure the radiator cap is of the proper specs & is new. 2. Make sure the thermostat is the correct type for the XK engine and the correct temp. 3. Install a coolant recovery system. 4. Acquire an XK-specific flex fan (from XKs Unlimited and other suppliers) & replace the stock fan with it. It provides a helluva lot more airflow across the radiator cooling fins than the stock fan does. You don't need to waste time cramming in an ugly electric fan if you do this.

The latter two recommendations will alter appearance & will no doubt cost you points in a Concours as the "bow-ties" look down their pointy noses at your alterations, so you have decisions to make. Either show or go!

My 120 fhc, with these changes, will idle in summer California weather without overheating now. - Mike Plechaty

Amongst many things affecting cooling, "overheating" is often caused by a mis-reading temp gage. Mine, after a complete re-build from a reputable restorer, read ten degrees C too high. The only certain indication of overheating is a boiling radiator. To check the gage calibration, remove it and put it in a glass of freshly boiling water with a mercury cooking thermometer, and compare the readings as the water cools. I believe most people will get a surprise ! As a standard for comparisons, my XK140 FH does not boil in traffic in summer in Pheonix AZ at 110 F and many stop lights. (New modern copper radiator core (same thickness), correct bypass thermostat, original water pump, rebuilt engine, electic fan). But I've learnt to subtract ten from the gage ! I think the XK140 had slightly better cooling than the 120 ?. Remember that electric fans make cooling worse at speed. And the boiling point is increased both by the pressure cap and the coolant mixture. John Spence

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