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GT6 radiator modification. Still some cooling problems. Is this "normal"?


RichardS
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I imagine waterless coolant with water still in it wouldnt be a good combination because you still got the corrosion potential of water without the protection of inhibitor in normal coolant☹️

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14 minutes ago, Jim-GT6 said:

Thanks Clive. Your breakdown of how to do this job is super helpful. Makes great sense. Really appreciate the step by step. Not sure I have the wherewithal or kit to ensure the gauge and sender are calibrated. Really wish I did.

I've added a new temp. sender, thermostat and voltage regulator (in addition to what was on it's way) so I can do my best to rule all those out. I think the regulator is worth a check as my fuel gauge hits the top end-stop when I fill it, way off the scale, and I imagine there can be a few causes for this, but I've been reading that the OEM voltage regulators can become poor with age and be thrown off by temperature. It certainly gets toasty under my dash! May as well change the regulator as it could easily be causing or confusing an issue, what with the whole 'always at 60% hot' thing too. I've ordered an OEM one from ANG, and I've also got a solid state regulator in my basket on eBay, as I'm tempted to try both. Are these any good? https://www.ebay.co.uk/itm/254122537915 More stable than the standard ones?

I've looked through the history, and found everything cooling related:

1991: Rebuild Radiator (Guildford Radiators Ltd £95 + VAT), Thermostat 88 degree, Hose set

2003: Recon exchange radiator assy (Six Spares, Teddington £120 + VAT), Radiator cap 13lb, Heater water valve, Thermostat 82 degree, Hose set

2014: Voltage stabiliser, Hose set

These jobs coincide with burst of receipts for all sorts of work, and there are big gaps in between.

Mileage I have references for: 1999: 85,627. 2002: 95,138. 2014: 95,145. 2015: 96,378. 2016: 96,652. 2017: 97,122. 2019: 97,267. late 2020: 98,249 (when I bought it) 2021: 00,118 (now)

If this is correct, it last had a last proper cooling overhaul in 2003, then barely moved for 11 years. It did 3k miles between 2014 and 2020.

Last rad overhaul 18 years ago, hoses 7 yrs ago, and 5k miles over the whole period.

Current plan:

1. Drain and discard the waterless coolant (no confidence it's <3% water, and it looks quite rusty)

2. Flush everything as described above, poke until everything is flowing, taking particular note of flow through the rear block drain

4. Once cleared, fit heater valve, front radiator cowl, 82 degree thermostat and 13lb filler cap (but keep voltage regulator and temp sender change in hand until after the test run to measure the flush effect using the same kit)

5. Fill with water+speedflush, run, check for improvement on the readings

6. Drain, refill with 30% antifreeze and water, fit voltage regulator and temp sender, go on another run, if it's changed, it due to the sender or regulator

If it's all not happy and stable after that, It either needs a clear-through of the block with the head off, or a recore of the rad., or both.

I know I've just repeated back everything you've collectively told me, but I can now print this as my to do list! 😄

Cheers,

Jim

 

 

That sounds like a thorough plan. Having done that, you will know for certain that all the basics of the cooling system are right.

Waterless coolant is a Marmite product, personally I'm not a believer and will not use it in my classics.

One point to add... Airlocks. When refilling with coolant, make certain the heater valve is open and jack the front of the car as high as possible, to encourage any trapped air out through the radiator filler neck. Start the engine without the filler cap on the radiator, then fit the cap after a couple of minutes, when air has burped out and you've topped up the coolant.

Nigel

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28 minutes ago, Nigel Clark said:

That sounds like a thorough plan. Having done that, you will know for certain that all the basics of the cooling system are right.

Waterless coolant is a Marmite product, personally I'm not a believer and will not use it in my classics.

One point to add... Airlocks. When refilling with coolant, make certain the heater valve is open and jack the front of the car as high as possible, to encourage any trapped air out through the radiator filler neck. Start the engine without the filler cap on the radiator, then fit the cap after a couple of minutes, when air has burped out and you've topped up the coolant.

Nigel

Thanks for the tip Nigel. I don't have a garage, and I was a bit unsure if all this would be easy on the flat in the gravel carpark, but if it's only a question of front end up for refill, and the rest is okay on the flat, we should be good. I wouldn't have thought to lift the front for the refill. 

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On 19/06/2021 at 04:41, clive said:

pay attention to the metal bypass pipe under the manifolds

Similarly the pipe that goes through the manifold, I blew compressed air through and the result was 'surprising'.  This means you need the heater valve off which you have mentioned.  Caution, when removing the old valve if it it does not move easily do not go mad and think a longer spanner will free it, it will sheer off and you are in a whole new world of pain.  Having tried all the usual (Plus Gas, diesel etc) in the end a cloth wrapped around the base soaked in vinegar for several days and it came out easily.

Dick

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I always wonder if the overheating symptoms will be different for dirty engine cooling passageways as opposed to a dirty or inefficient radiator. Surely the first will result in a hot engine with possible pinking and run on but not show in gauge water temperature or boiling over while the second could have all these? 

My thinking is that if the heat is restricted in escaping from the engine the water temperature will be normal or even lower if the radiator is functioning well. On the otherhand if you have high water temp then the heat is getting transferred out of the engine ok but not being liberated correctly to the air...

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there s a good few on here have used washing soda and it worked better than any £££ stuff

add it in hot water solution or spoon it in the flller about a good  2 mug fulls   or more 

give it a few hours of running hot and flush out well .with bottom hose off 

cheap  and effective   dont leave it in for days   it can attack the thermo hsg alloy

Pete

 

 

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1 hour ago, Dick Twitchen said:

Similarly the pipe that goes through the manifold, I blew compressed air through and the result was 'surprising'.  This means you need the heater valve off which you have mentioned.  Caution, when removing the old valve if it it does not move easily do not go mad and think a longer spanner will free it, it will sheer off and you are in a whole new world of pain.  Having tried all the usual (Plus Gas, diesel etc) in the end a cloth wrapped around the base soaked in vinegar for several days and it came out easily.

Dick

Another great tip. Thank you. I was looking at it and wondering how easily it will come free. On this - should I be putting anything on the thread of the new one when I fit it? To help seal it, and / or help it come undone in future? Is there a gunk or paste I should be using?

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17 minutes ago, Jim-GT6 said:

should I be putting anything on the thread of the new one when I fit it?

Jim

Plumbers PTFE tape works well.

Also regarding the tap in the rear of the bloc, remove the whole tap rather than just opening it.

I use a funnel and short length of tube set into a bung in the radiator filler to get a good head. I posted the procedure previously and will try and find it.

I have used the 2-part Holts Radflush before with good results.

Happy flushing.

Ian

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If you need to poke about to get water out of the drain plug there is probably a load more crud in there that you can get out with a bit of wire - or at least that was my experience.  I think flushing using holts or similar didn’t work for me.
Bob

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11 hours ago, Bob Horner said:

If you need to poke about to get water out of the drain plug there is probably a load more crud in there that you can get out with a bit of wire - or at least that was my experience.  I think flushing using holts or similar didn’t work for me.
Bob

+1

That's been my experience too.  The only way I could get the compacted crud out of the water jacket around cylinders 5 and 6 was cylinder off,  then dig it out with a small screw driver and flush with plenty of water. 

Nigel

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Further to another post re fan controllers not working, I ran it up to temperature in the garage last night to check out what was wrong. To get my GT6 up to temperature without a fan running in the garage seemed to take forever -  really reluctant to overheat.  I'd say about 15 to 20 mins or more of ticking over before got anywhere near hot enough for the thermostat to open.  Even then took a while for the gauge to start to creep up and the electric fan was only needed for a minute or two.  Prior to taking the head off and attacking the crud around nos 5 and 6, it would boil in no time at all.  One thing that I noticed was the bottom hose didn't get that hot which I assumed was because hot water didn't seem to be circulating around and into the engine at anything like the correct rate (indeed the in line temperature controller in the bottom hose wouldn't actually switch on as a result). 

I honestly can't believe the difference after the clean out and, as a result, from assuming the Gt6 was marginal cooling-wise due to received wisdom, I'd say it was better than the TR4 or the spitfire.  Heating/ overheating is a delicate balance and therefore, small restrictions like a build up of crud upset that balance I suppose.  

Bob

  

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An update.

I took my rad to Motorads in Redditch http://www.motoradsonline.co.uk/ which was recommended by my Son.

Andy, the chap on the desk, was extremely helpful and asked if I could wait whilst he took it off for some quick testing. When he came back he said that it was in pretty good condition and, although it was not operating at 100%, he was used to seeing far worse and would be surprised if the rad was the only issue.

We then talked about all the other work I had done and the symptom that whilst the car was moving it all seemed OK but after I came to a halt the temp started to creep up. His view was that I had done what was needed and that he also agreed that the rad now seemed to be the weakest link in the chain.

I did tell him that the Kenlowe did keep the temp down but he stated that they did not recommend after market fans and would not fit them because they caused other problems which, at this stage, he did not elaborate. His view was that with my cowling in place, an electric fan should not be required.

By this stage, Andy seemed so reluctant to actually accept the business that I was beginning to wonder if they had too much work on. Anyway, once we had reviewed all the options, he agreed to recore the rad but said that they were fairly busy so it would take a while. Here we go, I thought, so how long I asked. About a week he replied! Good grief .... I was thinking in months!

At this stage another chap walked in with a rad from a TR4 which was also fitted with a Kenlowe still in place. He said it seemed to have suddenly started leaking and could Andy take a look. Andy did that whilst me and the TR4 man chatted.

Andy explained that the plastic tie fittings for the electric fan had vibrated against the core and worn it through and it was now weeping. He said that they get a lot of rads in with exactly this problem which is why they do not fit fans using the plastic ties and that he could repair the leak but would give it back without the fan fitted as they did not keep any of the ties and the owner would have to re-fit it himself. Andy advised that he should get some brackets fabricated if he really wanted to retain the fan.

Anyway, there's quite a bit to think about there. I'll soon be £250 lighter so let's hope that it does the trick.

Richard

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if guys  knew how thin the tubes really are you would never tether a fan through the matrix as a means of fixing

its just sensless   hang a ruddy great vibrating motor and fan assy on tubes made from thin foil 

its  asking for trouble 

Pete

 

 

 

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On 20/06/2021 at 20:40, clive said:

A plain plug is 3/4" (18 or 19mm should work) At least that is what I remember.

It may be very tight. A few light taps with a hammer may assist.

 

Managed to remove the drain plug. It is 3/4AF but some of the corners were a bit rounded. Nothing came out apart from a flood of clean coolant so guess it must have already been looked at recently.

As everything else looked good I dropped the number plate a couple of inches (Spit 1500) and it has made a significant difference. Previously, the fan was coming on soon after I dropped below about 30MPH whereas now it doesn't until  I have been stationary for about 30 secs and switches off again soon after I'm on the move again.

My number plates have those cosmetic chrome effect surrounds fitted so slightly larger than standard which might have exacerbated the impact. It's only about 1/2" all round the edges but I suppose that adds up to several square inches of airflow blocked.   

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8 minutes ago, cliff.b said:

Managed to remove the drain plug. It is 3/4AF but some of the corners were a bit rounded. Nothing came out apart from a flood of clean coolant so guess it must have already been looked at recently.

As everything else looked good I dropped the number plate a couple of inches (Spit 1500) and it has made a significant difference. Previously, the fan was coming on soon after I dropped below about 30MPH whereas now it doesn't until  I have been stationary for about 30 secs and switches off again soon after I'm on the move again.

My number plates have those cosmetic chrome effect surrounds fitted so slightly larger than standard which might have exacerbated the impact. It's only about 1/2" all round the edges but I suppose that adds up to several square inches of airflow blocked.   

What temp is the fan set to come on? Many have them set too low, a hazard of adjustable switches. If you have an 82degree thermostat, it wants to come on at about 88-92 degrees if in the top hose. Sadly the temp gauge in the car is not always very accurate, but if the car runs bang in the middle at say 60 on the open road, the fan should come in at about 3/4.

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37 minutes ago, clive said:

What temp is the fan set to come on? Many have them set too low, a hazard of adjustable switches. If you have an 82degree thermostat, it wants to come on at about 88-92 degrees if in the top hose. Sadly the temp gauge in the car is not always very accurate, but if the car runs bang in the middle at say 60 on the open road, the fan should come in at about 3/4.

Fan thermostat is in the bottom hose and set to 85C so at that point I think the top hose would probably be towards the top end of the range that you suggest. Gauge now reads just under halfway when on the move and fan cuts in when just over halfway. 

Running on the drive with the rad cap off and a thermometer inserted the fan came on at 85C (No airflow through rad so assume lower hose temp roughly same as top) for about 10 seconds until temp dropped a couple of degrees. Leaving the car running, the temperature at the radiator oscillated between roughly 83C to 86C and the gauge either side of halfway, the same as when driving. 

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4 hours ago, cliff.b said:

Fan thermostat is in the bottom hose and set to 85C so at that point I think the top hose would probably be towards the top end of the range that you suggest. Gauge now reads just under halfway when on the move and fan cuts in when just over halfway. 

Running on the drive with the rad cap off and a thermometer inserted the fan came on at 85C (No airflow through rad so assume lower hose temp roughly same as top) for about 10 seconds until temp dropped a couple of degrees. Leaving the car running, the temperature at the radiator oscillated between roughly 83C to 86C and the gauge either side of halfway, the same as when driving. 

I like that. The proper way to check things out!

I think there is usually a 7ish degree difference between rad in and out, when moving or fan on. So your 85 in teh bottom hose sounds good to me.

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26 minutes ago, clive said:

I like that. The proper way to check things out!

I think there is usually a 7ish degree difference between rad in and out, when moving or fan on. So your 85 in teh bottom hose sounds good to me.

I might lower the fan cut in temp very slightly so it comes on almost immediately when I stop, but I don't want it to come on during normal driving unless there are exceptional circumstances.

As I can adjust while I'm driving it's easy to fine tune on the move or adapt to different conditions, if required.

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Another update ..... I actually collected the radiator on Monday as the guy managed to do the re-core a bit sooner than expected.

Before the re-core, there was a 3mm gap at both the front and the back of the frame between the frame and the core. They managed to fit in a bigger core which, I think has an extra row of tubes or perhaps just larger tubes, so that although the rad is the same size, both gaps are now gone.

They also said that the old core was rather slimy and messy but not actually blocked as far as they could tell.

I had drained the radiator into my large pan without losing any coolant but when I came to pour in back in I was about 700 mls short of coolant which I had to top up. I think this is due to the extra capacity of the new core.

Anyway, I took it for a high speed run this afternoon and then let it idle for 10 minutes or so and the temperature did not even reach 80 degrees which suggests that the thermostat was opening and closing and the cooling capacity was never actually reached. 

The issue could well be that it is around 8 degrees cooler today than it was the last run but we seem to be heading in the right direction.

Richard

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