I recently changed my thermostat, which led to replacing the thermostat housing which broke. While filling and bleeding, I noticed coolant dripping under the vehicle near the back of the engine. Not from a hose, but from a flap -- see attached picture. I'm not sure if it was leaking before or if it was something that justled loose, but I can't see any leaks at the top of the engine anywhere near the housing or the radiator. Any thoughts on what could cause a leak through this flap but which isn't visible from above and the front?

 

IIRC, that rubber “flap” is just a cover for an access port in the casting. I can’t remember what is behind there. Maybe it is to reach the bolts on the torque converter?

Regardless, the purpose of the cover isn’t important. I suspect you’ve got a leak up higher on the engine and it’s making its way down there.

Use a cooling system pressure tester to check for leaks. Running at idle creates very little pressure so most leaks aren’t apparent. You’ve also got to stay clear of moving parts. A pressure tester builds higher pressure so leaks are easier to find, and is done with the engine off for safety. If you don’t have one, some auto parts stores have free loaners.

 

I do have one so I'll try that out. Do you know if the blue arrow points to the heater return hose under the manifold that everyone speaks about? I specifically notice this being looser after I replaced the tower.

 

Won't be coolant leaking from there?
The sensor is your crank sensor and that flap is just a small access port cover over the flex plate.

Maybe just left over coolant from your repairs?
Dried coolant is usually pink/red and that looks rusty?
I would just drive some more and are you losing any coolant now?

One last comment?
The 4.0L V-8 is known to leak under the intake manifold. Has that hose been replaced yet?
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The hose under the intake manifold has not been replaced.

 

This thread shows what is under that cover:

https://www.jaguarforums.com/forum/s...sensor-274038/

In that thread, the OP was dealing with a broken CKP sensor, but at least it shows what is back there. It is mostly just the sensor tone ring on the front of the flywheel.

 

You may be on to something. If leaking there, wouldn’t coolant run aft and then behind the engine? Might explain what is happening.

 

Lovely. Would be great if someone who has replaced that hose can confirm that against the hose in the picture I posted earlier in this thread. I can physically feel it looser than it was before I was in there, so that would confirm it in my mind.

 

The hose won't be loose?
It just gets a hole in it?

Search for under valley hose and there are dozens of threads. Now the good thing is you don't have the SC'd engine so removing the intake is not that hard or complicated.

You have not mentioned it but now would be a great time to replace rubber coolant hoses and the DCCV. Remember the car is now VERY old! It's at least 24 years old! Does the heat and AC work properly on both sides?
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I did do some searching, but all of the results tended to be a bit later model and they all had SuperChargers, so wasn't sure how much of the layout changed between them.

I changed the front larger radiator hoses several years ago. That said, I plan to replace anything in that area that's tough to access. I wish someone had put together a list of all the things to do on my model when you're in there. I'm doing the forward and return hose. Is there an aftermarket DCCV or does Jaguar still sell those?

 

I would also replace the crappy plastic thermostat housing with Aluminum?
Here is a thread showing that part.
Thermostat Housing
Rock Auto has this for a good price?
Al. Thermostate Housing

Here is another thread that might help?
Valley Hose Replacement

Please use ONLY the Bosch DCCV! Much experience with this and be aware there are two different DCCV's? 3 hose and 5 hose versions. One on the 6 cylinder cars and the other on V-8's?
I "think" you need MOTORCRAFT YG355 for your DCCV and Bosch is the OEM supplier. But do check the part number. I see find this from several suppliers.
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If you find a DCCV through official Jaguar channels, it will be a Bosch brand in a very expensive box. Definitely stay away from the Fling Dung brand $30 specials found on eBay. Even the OEM part has a VERY high failure rate. You don't want to tempt fate with a cheap part.

These following links may be of interest. Both are on an early V6, so some details may be different with the V8.

If you want to change the entire valve:

JagRepair.com - Jaguar Repair Information Resource


I recently swapped out the guts and left the valve body installed. Saved a lot of hassle dealing with the hoses. Details here:

https://www.jaguarforums.com/forum/s...repair-251854/

 

I got here in the first place trying to change my thermostat, the nut on the plastic housing broke off, so I replaced it with the upgraded aluminum housing, and then after I put it back together and did the bleeding, I found the leak dripping from the back of the engine. Given there was coolant in the expansion tank, I can't imagine the leak existed before, so I suspect my hose shuffling when replacing the housing was the final straw with my valley hose.

It's not particularly clear to me why replacing the DCCV at the same time is needed. I don't believe that's underneath the intake manifold. I did test it a few years ago when my AC didn't work and it was good. I always buy OEM when I can, so I'd go with the Motorcraft part.

 

Brandon your picture shows the plastic thermostat housing? You have already installed the Al. version? Maybe after your picture?

The point is that once you start taking the engine apart you have done the majority of the labor. So rather than waiting for another hose/DCCV failure and having to go back in again. Replace things that are failure prone to save on labor. Of course if your like me and DIY the labor is free anyway!

It's just time and maybe you messing around in there made it show up sooner but many have that leak without touching the engine.
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Oh yes, good catch, that was before I took it apart and replaced the housing and thermostat. I'm always about fixing anything that's consumable (like hoses and gaskets) or error prone in the area I'm working in to get to what I need to replace -- i.e. things more accessible with the throttle body and manifold off, plus the gaskets, etc.

However, if it's unrelated on the other side of the engine compartment, like the DCCV, I tend to wait until those actually fail unless I'm having problems. But I do appreciate the advice.