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A Definitive Oil - Diesel - Stop Leak in Td5 Coolant thread.


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Bought a Disco II to get me there while I do a nut and bolt restoration on my RRC. I have to admit I like it, I really like it, but I'm glad I only paid a few yoyo's for it because it's been flipping neglected. Today's job was take the coolant system apart to investigate the stuff floating in the coolant expansion tank.

I've been googling like mad trying to find something definitive on identifying what the various things that can arrive in your coolant are, nothing solid, so here I am. I've taken some pictures of what came from my coolant system. It's very difficult to properly represent how it looks but they're below for anyone who can either shed more light or needs light shed.

There are four possibilities as far as I can tell:

1. Oil (from a corroded oil cooler) Can seemingly show up as black oil, and/or get churned up to an off white mayonnaise.

2. Diesel (from a leaky fuel cooler) Diesel I know least about but seemingly can sit on top of the coolant in the expansion tank and cover it all.

3. Congealed gunk (from incorrect antifreeze mixing with OAT type) Reported as reddish globs floating in the coolant.

4. The remains of some sort of stop leak additive in the system. (also described often as brown gunk floating)

My car has produced reddish brown floaters. I have no definite evidence that it's a result of incorrect coolant, or stop leak, but I believe it's one of the two based on the following:

1. I haven't lost any oil in two weeks of watching.

2. I haven't lost any coolant either. (I don't know the car well enough to know where temp needle should be, but it sits solidly in the horizontal position, pretty much dead centre on the gauge and just above the wavy line of the level symbol.)

3. Diesel couldn't possibly be getting into the coolant because it has an unrestricted flow out of the car through the pressure reg. (that's a joke :D )

4. My coolant isn't the colour of any OAT coolant I've ever used. If I had to say it had any colour I'd say it had the palest tint of green, or maybe that kind of barley water colour. The photo's you'll see make it look brown/red but that's just from the accumulated carp in the expansion tank. I'm not even convinced it's not just water.

5. The car has a new rad and thermostat (dated 2012), which could point to a leak in the old rad that someone attempted to repair with stop leak.

6. I'm fairly sure the amount of gunk in the expansion tank hasn't increased since I bought the car. But inconclusive.

Speaking of the 'stat, it seems to open late. The temp gauge comes up in a normal time to about 1/4, and sits there for maybe 10 minutes and then suddenly opens fully and the gauge comes up to working temp. But I put this down to the red/brown gunk that was in a thin layer over the thermostat internals. I did put it in a pot on the cooker this eve and it opened before the water started to simmer (after I'd cleaned it thoroughly).

Today I flushed as much of the cooling system as I could with a hose, but something strange - I put the hose directly into one of the heater hoses and then the other. The one that goes from the rad to the fuel cooler wouldn't accept any water. It just backed up and forced the hose nozzle to pop out. What's the story there?

So here are the pics. I should describe this stuff. It's not unlike mayonnaise (the car type) in initial texture and it is kind of gloopy but actually not hugely greasy. If you rub it between thumb and index (wearing laytex gloves) it seems to get more viscous, almost sticky, and less willing to lubricate. Once rubbed in like that it takes a fair amount of rubbing with neat fairy liquid to clean off. Some that I rubbed on a rag yesterday, and was thick and sitting on top of the rag at the time was reduced flat by evaporation today and almost dry. It floats but as you'll see it sticks easily, this bottle hasn't been jostled too much. Oh and if it is, the smaller bits don't make a B line to the surface, they will swirl around for quite a while and will sink.

This could still be oil from the cooler, or a head gasket tell tale. The Td5 is very good at not always showing typical symptoms. So any input from anyone with experience would be great! I hope in the meantime this helps someone else with similar symptoms.







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Looks like accumulated gunk from years of neglect to me. Personally i would drain the system down, refill with water and add a few spoons of washing powder (biological kind) then run for a few days, before flushing with clean water and then adding the correct antifreeze. Green (or blue) is usually ethylene glycol based, rather than the usual pink/orange OAT brand.

A few years ago Ford started using 10 year long life antifreeze, which was a nice purple colour, and if the LR cooling systems were more reliable, then i was going to use some of that in my previous 300 TDi.

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I've used dissolved SODA crystals... That was the 2nd attempt and very successful. I'd actually misheard the instruction from my mate the first time round and used Lux SOAP crystals. Holey smokes, that produced a lot of very fine bubbles that pumped out of the overflow pipe... Unfortunately I was a mile into the "thrash it clean" trip, and had made it down the high street in the village... Laying my own personal white lines. Even a blind man would have been able to follow the trail back to my house!

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Don't use dishwasher tablets or anything of the like. I know a guy who ruined his engine using that.

That stuff starts to foam like mad and your waterpump isn't made to pump air,just water.

On top of that. Everywhere where there is foam in the waterjacket the metal of the cilinderblock and head can't dissipate their heat to the coolant resulting in een engine that overheats.

Just get a bottle off radiator flush. They're not expensive and meant for that purpose.



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  • 1 month later...

Thought a follow up was in order:

I took the rad, thermostat and expansion tank out of the car and flushed/washed them as meticulously as possible. I used elbow grease and washing up liquid on anything I could get at. The termostat was fairly gunked up with that goop, and plenty of it came out of the rad too.

In the meantime I took a hose to the remainder of the system in the car and flushed/back flushed it until the water ran clean.

I made up a solution by breaking up about a 1/2 of a dishwasher tablet into 1.5L of water and shaking vigorously, and put that in the system while refilling. I drove the car for 20 - 60 mile journeys in between flushing the system 5 times until I was satisfied I had gotten all traces of detergent out of the system. It never frothed or lathered more than a few weak bubbles in the expansion tank even in the beginning. Finally I refilled with 50:50 OAT antifreeze:water.

Since mid-late December all has been fine (bar a weep from the bottom metal coolant pipe, that needs brazing). So it seems it was just a congealed mix of the wrong coolants and general neglect. There is a small residue of that brownish goop in the expansion tank but it's so fine I'm sure it's only residual grime.

Thanks for the help gents!

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My gauges on my 109 and soft dash RRC do the same thing, and each has mint condition cooling systems. I think that jump is normal, perhaps because the gauge is more sensitive in the middle of its arc where is should normally sit

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Sorry Divster, just noticed this now.

Yeah the temp gauge still does that.

I think what's happening is that the coolant temp sensor is on the cold side of the thermostat and the sudden jump on the temp gauge is the flush of hot coolant being let through as the thermostat opens.

I tested my thermostat in a pot of hot water while I had it out. It was working fine. I noticed that there's a small hole in the metalwork inside. It allows a small stream of coolent to pass through at all times. Without this I presume the length of time the tstat would take to open would be greatly increased.

Initially I thought the gauge thing might be a problem because my other Td5 doesn't perform like that. But then I remembered I have a custom temp sensor set up towards the top of the system because of my engine conversion. :rolleyes:

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