A small puncture in the throttle body heater hose sprayed yellow-colored gunk in the surrounding area.



I opened the coolant reservoir cap to discover more of the butter-like gunk.



I suspect an internal leakage has developed in the radiator core, causing transmission fluid to mix up with engine coolant. What are your thoughts, guys?

 

Only other source would be engine oil through a crack somewhere in the engine block (very unlikely). If the oil fill cap/dipstick show normal oil (no "milkshake"), 99% chance it's ATF leaking from the oil cooler in the radiator.

 

If it's trans fluid I'm surprised the gearbox isn't acting up. Please keep us posted on how you get this resolved and good luck.

Regards
Jeff

 

There is no "milkshake" on the dipstick, and I do not see any looking down the oil refill tube. So the conclusion is ATF leaked into the radiator.

 

My question is "Does the ATF run under higher pressure than the engine coolant in the radiator?"

The pressure cap on the expansion tank is marked 140kPa which is about 20.3psi, so the pressure of the coolant is less than 20.3psi.

I don't know at what pressure the ATF is being circulated to the radiator for cooling, but it appears to be higher than the coolant pressure, resulting in the milkshake formation. The ZF 6HP has definitely lost some ATF, but has not acted strangely so far due to my early detection. After replacing the radiator, I shall also flush the transmission and completely replace the possibly contaminated ATF.

 

Engine oil and antifreeze is usually gray. Yellow is a new one on me

 

Could be mixing coolant types? Bit of green coolant being added to orange OAT could produce that? Perhaps try a coolant system flush first? Gonna have to drain down to remove the radiator anyway?

 

Most likely you face an emulsion of ATF and coolant, caused by an internal leak in the cooler. It will be an exciting job to remove the stuff from the gearbox and the entire cooling system.

Fritz

 

Not sure that mixing green and orange gives you yellow. If you mix green and orange antifreeze, it turns to jelly. But in the artist world green and orange would be a bluish purple wouldn’t it? Anyways having never seen yellow come out of a hose leak before so I googled it and I found this article that talks about a yellow antifreeze made for certain cars. Any chance some previous owner may have put in a yellow antifreeze?https://www.cashcarsbuyer.com/what-h...r-antifreeze/#

 

He was supposed to talk about a yellow coolant

Antifreeze changed from green to bright yellow. - Club Cobra

 

I’m actually finding a lot of things on the Internet about coolant changing to yellow so maybe you want to do the same Google search that I just did which was “why did my antifreeze turn yellow” and read some of the posts

https://www.dsmtuners.com/threads/gr...orange.162567/

 

I have just read the owner's handbook again cover to cover and saw no mention of a transmission dipstick, as per Jaguar's usual zero-maintenance practice with ZF boxes.

My first job is to open the transmission refill plug to take samples of ATF at different levels to look for any contamination. Before taking the samples, I can also roughly feel how far down is the ATF sitting below the plug opening.

Stay tuned for the progress...

 

@Aarcuda Thank you for your extended research into coolant changing in colour. Unfortunately mines not the case.

@flatsix As you so rightly pointed out, I have an emulsion in the radiator caused by a mixing of coolant and ATF from an internal rupture. This milkshake is smooth but does not feel very oily by finger.

As I do not have a good floor jack as well as floor stands, I would need time to source these tools before I can get underneath the transmission to start investigating.

Stay tuned for the progress...

 

Is your trans cooler in the radiator? Bc mine in my STR is separate.

you could try removing a trans line and see what drips out

 

yes, left hand side of the radiator.

Do yourself a favour and do the job on a lifter. Acces to the tranny refill plug is a bit difficult because of the near by exhaust pipes. If you loosen the refill plug while the engine not running be prepared of an ATF shower.

In my opinion the issue is a good opportunity to remove the oil pan and have the ATF changed.

Also draining the radiator is mostly a big mess, the unfortunate position of the drain plug ensures that the coolant spreads around. You are advised to suck as much as possible coolant from above ( reservoir an hoses).

Fritz

 

In my judgment, it's a seal under head. I also saw a yellow cappuccino.
Try the expansion tank pressure test and the exhaust gas expansion tank test.

 

wait im an idiot. That was the power steering cooler I was thinking about. My trans cooler is also in the radiator. I just remember repairing the lines and disconnecting them on the radiator! DOH!!

 

That's an excellent idea negating having to crawl underneath the car to get at the tranny fill plug. Now, why didn't I come up with that earlier? Thanks, Aarcuda.

Stay tuned for the progress...

 

Ideally, I should be opening the bottom transmission line into the radiator to check if coolant has entered the ATF circuit, but that location is just as difficult to reach as the refill plug on the side of the transmission. I ended up loosening the top transmission line to let out some ATF and I do not notice any coolant contamination, which doesn't positively proof no coolant has entered the system as water is heavier than ATF

I have already ordered a replacement radiator from eBay which costs less than $200 shipped and will take about 2 weeks to reach Hong Kong. That will give me time to further consider whether to abandon repairing her or to find a reasonable replacement Jag on the market.

Stay tuned for the development...

 

I think if the two were mixing and it was run for any length of time that you would see mixing all throughout the system