Which coolant for a 4.0L in 2022?

[V]

My 2001 4.0L XJ is overdue for a coolant change. I actually didn't record when I last changed it but I remember doing so when other stuff was going on in my personal life so I have a rough date anchor to go by. If I am correct I am overdue by a year. I have topped it up with a 'universal coolant' which I understand is OAT and can reduce the effectiveness from 5 years to 2. It had Chrysler HOAT from new, but they quietly changed to OAT (Dexcool) around 2012/2013 and I didn't notice that I was putting in a different Chrysler coolant than before as the colour was the same. I have both types of concentration float gauges (Ethylene and Propylene), what's in it now still shows up as being effective to single digits below freezing when I last checked a couple of months ago.

 

My 1993 4.0L had an unscheduled replenishment of coolant a few weeks ago. I usually put old fashioned ethylene glycol in it every two years but I am wondering if I should switch to a universal OAT for both of them. I need to change the spark plugs this week. It's a job that requires draining the coolant to remove LPG components that are in the way of plugs 4,5&6. Now seems as good a time as any to fit a new water pump and replace the top and bottom radiator hoses.

 

The coolant I am interested in is ChemFlow 40. Do you think this is a reasonable plan? I guess the gauge I should use to check concentration next year is still the ethylene glycol gauge.

[Vernon]

14 hours ago, V said:

My 2001 4.0L XJ is overdue for a coolant change. I actually didn't record when I last changed it but I remember doing so when other stuff was going on in my personal life so I have a rough date anchor to go by. If I am correct I am overdue by a year. I have topped it up with a 'universal coolant' which I understand is OAT and can reduce the effectiveness from 5 years to 2. It had Chrysler HOAT from new, but they quietly changed to OAT (Dexcool) around 2012/2013 and I didn't notice that I was putting in a different Chrysler coolant than before as the colour was the same. I have both types of concentration float gauges (Ethylene and Propylene), what's in it now still shows up as being effective to single digits below freezing when I last checked a couple of months ago.

 

My 1993 4.0L had an unscheduled replenishment of coolant a few weeks ago. I usually put old fashioned ethylene glycol in it every two years but I am wondering if I should switch to a universal OAT for both of them. I need to change the spark plugs this week. It's a job that requires draining the coolant to remove LPG components that are in the way of plugs 4,5&6. Now seems as good a time as any to fit a new water pump and replace the top and bottom radiator hoses.

 

The coolant I am interested in is ChemFlow 40. Do you think this is a reasonable plan? I guess the gauge I should use to check concentration next year is still the ethylene glycol gauge.

I stopped using OAT antifreeze on older vehicles when it became evident that it can attack rubber and silicone.

 

A Td4 engine in particular suffered O ring failure that looked like the O ring had exploded from the inside out.

 

So I’m happy using “Blue” and will change every two years.  

[V]

I found this useful info from the Federation of British Historic Vehicle Clubs.

 

It appears that the companies producing the new fangled antifreeze formulations cannot agree on a standardised colour scheme. Even worse is that they have started making blue coolant too, so that it is now impossible to buy antifreeze without knowing exactly what is already in your engine's cooling system.

 

It appears that the ChemFlow 40 antifreeze I was interested in is a type of Hybrid Organic Acid Technology because it contains silicates as a corrosion inhibitor. However, after speaking to ChemFlow tech support they did not consider their product to be a hybrid, but a reformulation without the harmful and damaging ingredients of the earlier OAT formulations. The OAT formulations that got a reputation for damaging gaskets and seals in older vehicles did not contain silicate, but did contain other ingredients such as borates, phosphates and nitrites.

 

The ChemFlow tech support guy could not say how long the coolant would be effective as an antifreeze. He said that the vehicle manufacturer's intervals are based on brand new engines that have no deposits in the cooling system. On old engines with crystalline structures coating the cooling system, antifreeze is less effective and may need changing sooner. The dirtier your engine's cooling system is, the less effective the antifreeze will be. He recommended draining the existing coolant and flushing with clean water. Then refill the system only with clean water and bring the engine up to operating temperature on a test drive, dumping the water only coolant as soon as it has cooled enough to do so. He said to do this at least once or as many times as necessary before clean water is all that comes out of it. He then suggested using ChemFlow40 on a weak mix of 25% antifreeze / 75% distilled or deionised water. This would help clean the galleries of any coagulated sludge over a few weeks. If the coolant remains clean then it could be topped up with antifreeze to a higher concentration 33% or 40%. If the coolant is dirty then drain and replace with the concentration that you require.

Edited October 26, 2022 by V

[V]

I think I am going to take a chance on ChemFlow 40 or one of the other universal coolants based on monoethylene glycol in both of my 4.0L engines. I have looked at the tech and safety data sheets of a number of products that have a non-NAP OAT formula with added silicates. They all appear to be suitable with gasket materials, rubber and silicone hoses. A five year interval is claimed with most of them, but all state that when mixed with another ethylene glycol based antifreeze that the interval is reduced to the product that is already in the cooling system. I am not sure how to interpret this. It could mean that a 2 year traditional coolant topped up with a universal antifreeze after 18 months, only has 6 months to go before it needs replacing. Or it could mean that the mixture of both will be good for another 2 years, not 5.

 

My assumption based on the above ambiguity is that when converting to a universal antifreeze after draining and flushing, don't expect more than two years of protection from the universal antifreeze. On the next drain and flush it would be reasonable to expect between 2 and 5 years of protection. If just topping up traditional coolant with universal, it wont extend the protection interval. The coolant should be changed two years after the last complete refill.

[Vernon]

Interesting stuff V - many thanks.  A great update on what’s currently going on.

 

Having seen the damage the original OAT antifreeze inflicted - I am extremely wary of what I now put in a vehicles cooling system.

[digger]

I'm quite concerned re this. I've said else where that the colour means little these days.

In my case I thoroughly flushed the system  in my 4.0l a few years ago using what I have always used, central heating flush!  Then I flushed well with clean water and added  50% antifreeze meeting the Jeep spec. This had a 5yr life and I was going to change it anyway this winter(4 yr) in my big refit. As a matter of interest I top up (seldom needed) with the same mixture and check with a hydrometer.  However , my 'coolant' hydrometer is not calibrated, it just has coloured bands and percentages. Therefore I think it is likely to be inaccurate if used with other chemical formulae. I suppose one could mix up any new formulation, check the reading and use that as the optimum base line. I do have two other calibrated hydrometers some where but would have to check with the new formulations you describe as to what the density should be at different concentrations. it may be possible to find this out but otherwise I would measure specific made up concentrations to establish data.

[V]

4 hours ago, digger said:

in my 4.0l a few years ago using what I have always used, central heating flush!

That sounds interesting. Does it remove calcification? I have heard of people using Coca-Cola + water overnight. I wondered if a 10% white vinegar + water would work left overnight. I don't know if anyone has ever tried Calgon.

[digger]

I have used central heating cleaner because it comes in a larger bottle, which is enough for a house. It works out cheaper, you don't need to use it all in one go. My logic was that the components in CH are similar to a car ie  copper, solder, brass, rubber, plastics, gaskets, steel, felt washers etc. It certainly cleans it out! PH is usually on the low acid side of 7. I could be out of date and the chemicals have changed, but the materials are still the same. If you leave it in a CH system for a couple of weeks it neutralises itself, as far as I know - because it reacts with the sludge, scale etc. I leave it in the car  much less than this, perhaps a couple of days driving around! 

I always put boiled water in the radiator. It may not be as good as distilled but I have never had any problems. 

I would have thought white vinegar would need to be much stronger in concentration to work effectively, maybe 50% with water.

Interestingly 'grannies mixture' is an emulsion formed from 50/50 white vinegar and yellow washing up liquid!! (not in rads! serious bubbles I guess). As I've said before many times,  it is an amazing cleaner.

Coke , I think has Carbonic acid from CO2 and very dilute Phosphoric acid. The latter in concentrated form (care!) is the only acid I know of that will attack Aluminium. This is because it dissolves the oxide coating the alloy, thus allowing it to attack it. I wouldn't put Coke in my rad. In theory any acid will attack alloy if you can remove the oxide but even mechanical removal is useless because it reforms too quickly. I know, I've tried removing alloy from a bore(alloy seized on) with scratch and acid - useless! However with care one can remove the alloy from a bore with conc Phosphoric. It works well!

 

I can't recommend anything I do.  In days gone by a radiator leak could be fixed with a raw egg in the rad!

[V]

I have been reading some of the central heating product instructions and found a few warnings concerning aluminium components. Generally, they reckon they work in 1 hour, shouldn't be in a heating system for more than 4 weeks and if there are any aluminium components, no more than 3 hours. As I have no idea what concentration to use, I am going to chicken out and just use a bottle of Holts Speedflush for car coolant systems.

 

I am thinking that perhaps, there is more of a long term reliability advantage for flushing and changing coolant every two years as opposed to five. Two years gives less time for calcification to build up internally and doubles the cleaning flushes. Instead of converting the 1993 to a five year coolant change, converting the 2001 to a two year cycle may be better for it.

[digger]

Sounds fine to me. Your last comment can't be bad. Its why I'm doing mine again now. I've been saying for years that the majority of problems re Alloy heads/ iron blocks(like XJ diesels) are caused by infrequent changing/incorrect anti freeze  plus overheating. I like to flush mine thoroughly by connecting a hose to alternate places and running water though. I hadn't thought before but my CH engineer has a power flush washer for CH systems???? Maybe not!

 As for 2yrs/5 yrs there was atime when it was said that 2yr AF was blue and 5yr was orange. Of course I had to ask ''what are the green ones then?''

I didn't mean to miss out Aluminium in my list above.

Cars are increasingly being built to minimise servicing requirements. Another reason that services are such a rip off!

Interesting comments re Aluminium. Alkalis attack aluminium as I'm sure you know with the exception above , acids do not. Calcium deposits are eroded with acid as far as I'm aware. This suggests to me that some formulae have been changed. It could be because CH systems have an increasing amount of plastic in them and or a reducing amount of Aluminium. It is also possible that the makers assume that distilled water only is used in cars (Though not in CH) in which case calcium deposits will be lessened.

I wonder whether adding extra inhibitors would be an idea! I think their 'time' comments' are back cover!

I'd love to know how the active ingredients of Speedflush  compare to Fernox F3?

Edited October 29, 2022 by digger

[carls925]

Hi, might be worth a mention, I used newer OAT antifreeze in my 98 4.0l it took my core plugs out 3 out of 4 started leaking same time, leaked so much in a week had to change them straight away. was told due to antifreeze, core plugs were ally, can swop them for brass ones. all ways made sure used distilled water and correct antifreeze for early vehicles.

[V]

For that reason alone, it is safer for me to stick with old fashioned ethylene glycol. I found a local manufacturer where I can get concentrate for £1.40/Litre including shipping.

[digger]

I'm amazed that the core plugs are alloy! The only ones I've ever replaced have been steel !  Is that stock with the 4.0L?

[V]

I will look at both of my engines tomorrow to see if the later one has alloy core plugs.

[digger]

Just thought, actually I guess the calcium deposits are minimalised these  days even if you use tap. At the end of the day there is only a certain weight of Ca in a given quantity of water. These days,in my experience there is very little topping up required because the system is effectively sealed and there are less leak problems.  On the other hand, in olden times there was constant topping up which clearly kept 'topping up ' the Ca in the system which would then  be deposited!

Edited October 29, 2022 by digger

[carls925]

Digger I was wrong..I had to check now to see if core plugs are ally or steel they are mild steel, they are soft because they are the weak link to pop, if water froze so block dosent crack, but being mild steel, soft enough that the wrong anti-freeze finished the off.  

[digger]

Ok, no prob. I actually thought they were a type of  sprung steel which is why you can 'pop' them in and they stay in.

Um, when I've replaced them , one might have failed but they were all rubbish when I removed the rest. I've never done them yet in a Jeep!

They can pop out when frozen but don't believe it will necessarily save your block!

Edited October 30, 2022 by digger

[V]

I was sent a link to a feature article on coolant today. Reading it helped me appreciate why mixed iron/aluminium and aluminium engines can benefit from the modern coolant formulas and the importance of using a flushing chemical.

[digger]

Interesting article. 

It reminds me of two forgotten race things.

First ,his comments re water pump speed. We found different water pumps varied engine temp and therefore power on the dyno. I can't remember exactly but we also learnt the importance of fast warm up.  Until about 50% of normal running temp power was down as much as 10%! Mind you piston clearance was down  3 thou in a Nikasil liner bore.

Second. the picture etc of bubbles  and the mention of the contact area.  Its not just the 'bubbles'! If you splash a bit of water onto a hot plate it immediately scatters into balls, I'm sure you have seen this! One can buy an additive which alters the surface tension of the water so that it spreads evenly thus increasing surface contact. The one we used to use was called '' Water Wetter''

When I began with the Yj I flushed  as described, tested thermostat, fan etc.  Since then (fingers crossed) I haven't had any over heating issues which seems to be a common complaint I hear about.

[V]

3 hours ago, digger said:

the picture etc of bubbles  and the mention of the contact area.  Its not just the 'bubbles'! If you splash a bit of water onto a hot plate it immediately scatters into balls, I'm sure you have seen this! One can buy an additive which alters the surface tension of the water so that it spreads evenly thus increasing surface contact. The one we used to use was called '' Water Wetter''

I think this is the claimed advantage of those expensive 'waterless' coolants.

[digger]

Ah, that's interesting, I've only seen folk like Ed China using them. Certainly expensive and I think it falls into the category of ''is it really necessary''.

 

It never failed to amaze me , the number of people in motor sport who came into our tent, enthusing about their latest gymick, gizmo, new plug, brand etc telling us it had taken ''3/10ths'' whatever, off their lap time. I just put whatever it was on my dyno back home. 9 times out of 10 there was no difference or it was worse!!!  It did increase the size of the hole in one's pocket though! 

 

Just remembered. On very hot days overheating could be an issue. We used to increase water volume by lengthening the water pipes (by going round the seat or something!) which usually solved the prob quickly and easily. On one memorable, extraordinarily hot, weekend half the entrants seized. We  put an extra , spare  rad behind the seat as well, between heats! Problem solved, nothing fancy or expensive, but guess how many super 'water pumps', 'alloy rads', 'special drilled' heads, 'fancy pistons' etc popped up from the trade boys!   Ah well, good luck to them!

Edited November 5, 2022 by digger

[digger]

Extra cooling ideas. Larger longer, route changed heater pipes with surface area increased. Add small rad in the pipes. Fit larger heater matrix. All these can be used as needed too. If you are concerned about the extra heat in the cab in hot weather then fit a bypass to exclude the cab matrix and put extra small rad in the bypass. Hope these help!