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V8 radiator replacement


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I know the V8s have a different ECM to the 4-pots, but on my S4s I believe the fan override wiring to have been the cause of my ECM's demise due to the lack of a protective diode. Not sure if the same

Undertray rusty brackets. Be creative with some stainless steel, cobalt drills and grinding tools, and some epoxy and glassfibre. I also made a jig first.  

Finished and ready to go on the radiator 👍🏻

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Hmm... it's a dual tank set-up with two separate pressure cap.

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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9 minutes ago, mike_sekinger said:

Hmm... it's a dual tank set-up with two separate pressure cap.

Not on the later cars, Mike.

S4s and GT3 use a single Peugeot 205 header tank that looks like a cow’s udder, which has a hose connection to/from the top of the charge cooler itself. This is presumably to accommodate expansion. The systems are therefore not separate.

Margate Exotics.

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Oops - excuse my ignorance.  I'll stick to comments on the V8 🙂

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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  • 5 weeks later...

Metro,

Have you repaired your radiator tray yet?

I’ve done mine, I just cut out the old parts ,made some stainless brackets and fibre glassed them in. Came our well. 

Nearly in a position to reinstall. Just waiting on some more replacement snapped off fasteners!!

One tip. The air con pipes that connect to the condensers were semi seized and hard to get off. I didn’t want to wreck the threads on the new condensers. So I made up some thread chasers to clean out the female threads on the connecting pipe work . I purchased some steel pneumatic adaptors cheap online. A 5/8 and a 3/4 UNF, I then cut across the threads at 90 deg’s to make some slots . I screwed these in and out of the hose ends to clean the threads. They go on by hand now.👍

 

 

 

 

 

 

 

 

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Soak the pipe ends in caustic soda / hot water bath and ensure you are outside and at a safe distance. It will dissolve completely the aluminium in about 15-20 mins

Only here once

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13 minutes ago, Barrykearley said:

Soak the pipe ends in caustic soda / hot water bath and ensure you are outside and at a safe distance. It will dissolve completely the aluminium in about 15-20 mins

Barry that would be a lot easier But! the threads are attached to an aluminium pipe that you need to keep! 2nd photo. 

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9 hours ago, andyblackman777 said:

Metro,

Have you repaired your radiator tray yet?

I’ve done mine, I just cut out the old parts ,made some stainless brackets and fibre glassed them in. Came our well. 

Nearly in a position to reinstall. Just waiting on some more replacement snapped off fasteners!!

One tip. The air con pipes that connect to the condensers were semi seized and hard to get off. I didn’t want to wreck the threads on the new condensers. So I made up some thread chasers to clean out the female threads on the connecting pipe work . I purchased some steel pneumatic adaptors cheap online. A 5/8 and a 3/4 UNF, I then cut across the threads at 90 deg’s to make some slots . I screwed these in and out of the hose ends to clean the threads. They go on by hand now.👍

 

 

 

 

 

 

 

 

84B9A8CC-EC06-4639-8F06-342CD73CEF7C.jpeg

A311A9F3-F13B-48FD-B332-617E9E52542F.jpeg

2180BF9D-FCCD-481C-A59E-91BA7E931407.jpeg

70D97B07-E20F-44E7-A642-60D5F05D6EB7.jpeg

Hi Andy, unfortunately I haven’t had chance to look at it yet due to stripping the suspension off the car.  I got replacement support brackets from SJ to fit in but I’m not sure if I’m just going to buy a new tray assembly.  I’m terrible at fibreglassing and by the time I’ve bought a kit and sanding bits and the time it would take me I might just bite the bullet and get a new one.  
 

you have made a fab job of your repair 👍🏻

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  • 2 weeks later...
  • 1 month later...

Finally I found the solution to the overheating issues of Lotus Esprit V8. My mechanic installed a switch to turn on manually the fans. So whenever I am stuck in traffic, or right after spirited driving when I slow down, I turn the switch on and the fans start operating cooling off the engine !!

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I would suggest @MD355 you still have something wrong there. A nice manual switch is helpful - but is the rad pack full of dead flies and road detritus 

Only here once

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I know the V8s have a different ECM to the 4-pots, but on my S4s I believe the fan override wiring to have been the cause of my ECM's demise due to the lack of a protective diode. Not sure if the same driving mechanism from the ECM applies to the V8, but worth considering if you plan to use the override long term.

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28 minutes ago, tomcattom said:

I know the V8s have a different ECM to the 4-pots, but on my S4s I believe the fan override wiring to have been the cause of my ECM's demise due to the lack of a protective diode. Not sure if the same driving mechanism from the ECM applies to the V8, but worth considering if you plan to use the override long term.

What you are saying is that the override switch can cause damage to the engine ECU (ECM is ECU right ?) ?

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In the case of my car, yes I believe the way the previous owner wired in the fan override fried one of the QDMs on my ECM.

I don't know whether the V8 ECMs have any form of inbuilt protection or not, but if not I'd be inclined to suggest the use of some form of protection diode. Hopefully someone more knowledgeable on the V8 ECM can confirm/refute what I'm saying. Being a more modern design it may well have protection but I don't know.

The lack of a protective diode shouldn't be an issue short term, but long term it could kill the ECM if it doesn't have built in protection.

 

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I must be missing something here-is the radiator overheat sensor a simple open or shut-to-earth sensor? So a switch wired in parallel to it to earth or infinity would give an identical input to the sensor?

If not, that might explain why the ECU wouldn't like the input, but if it is just "earth" or "infinity" the ECU would not know the difference.

Happy to be educated!

 

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1 hour ago, LotuStuart said:

I must be missing something here-is the radiator overheat sensor a simple open or shut-to-earth sensor? So a switch wired in parallel to it to earth or infinity would give an identical input to the sensor?

If not, that might explain why the ECU wouldn't like the input, but if it is just "earth" or "infinity" the ECU would not know the difference.

Happy to be educated!

 

Exactly, that's what I thought !! My mechanic brought in a car electrician and he put this switch on the central tunnel right next to the tank opening button and alarm bypass switch... It is a simple on/off switch and I believe he did his electrical work inside the front trunk where the relay/fuses are...

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Just looking again at the post, i see the following..." the way the previous owner "

so who knows how the other one was wired in! Still, the question stands-is the V8 sensor just a switch to earth or infinity?

Reminds me of another forum I am on, where a guy said about a problem he had had  "...I was advised to check for yellow gunk in the oil..." and so we assumed he had checked the oil.

Two pages later, it turns out he had no oil in the car-no reading on the dipstick! He had not checked the oil, even after having been given that one piece of advice and specifically repeating it on the thread. Meanwhile he had spent hours replacing a difficult to reach fuel filter....

Ho hum...

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2 hours ago, LotuStuart said:

I must be missing something here-is the radiator overheat sensor a simple open or shut-to-earth sensor? So a switch wired in parallel to it to earth or infinity would give an identical input to the sensor?

If not, that might explain why the ECU wouldn't like the input, but if it is just "earth" or "infinity" the ECU would not know the difference.

Happy to be educated!

 

If we ignore the override for a moment, the fan is controlled via a relay. One side of the coil on that relay is connected to +12V and the other to the ECU which controls the ground. When the ECU doesn't require the fans on it drives its output pin to +12V which prevents the relay coils energising and thus the fans don't come on. When it wants to enable the fans is drives its output to earth energising the relay coil which turns the fan on. In the case of the S4s this circuit on the ECU is providing this control through a QDM device, which internally is essentially just a transistor.

In the case of my car, a previous owner connected a switch between the ECU side of the coil and ground to bypass the ECU control. While that had the desired effect of turning the fans on/off independent of the ECU it also provides an unprotected path to earth from the ECU output when the ECU is trying to drive its output to 12V to turn the fan off. At this point my electronics knowledge is a bit rusty and I've not investigated my ECU or the QDM datasheet thoroughly yet to try and determine the likely cause, but my suspicion that the ECU QDM got burnt out by voltage spikes caused by the use of the manual switch, backfeeding of the ECU output or the fact that you're essentially shorting the transistor output to ground on the ECU. 

I've never looked at the V8 ECM, so I don't know what components are controlling the fan output or if there is built in protection for overrides like this. Mine worked fine up to the point where the ECU died and it did it without warning, I've also got no idea how long the override has been in the car, so it might last years like that, I simply don't know. I'm just urging caution if you don't want your ECU to follow the same fate as mine.

 

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Ahhh.

Thanks Tom, as suspected and as you noted, it was the way it was done that fried the ECU.

Jeez. Shorting out the ECU is crazy! I suppose it must have been easier to reach the ECU than the radiator sensor. Typical Lotus problem, and also due to pure presumption from the person who wired it up. A little knowledge is a dangerous thing.

 

Talking of typical Lotus problems, I have a weak horn to fix, which is simple, but physically getting my hands on it is a PITA. So i have a horrible duck fart honk at the moment.

Maybe once it warms up a bit I'll give it a go. And before the MOT.

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Modern vehicles use the ECU to control the fans not because it's simpler for them to do so but because the ECU also controls the fans for the A/C and to adjust the idle to take into account the additional electrical load from the fans.

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