Weird Coolant Leak
 

The Jag gods have frowned upon me again :-).....


I am experiencing an "intermittant" coolant leak originating from the front left side (drivers) of the car. I have experienced this a couple of times in the past 2 years but generally ignored it as it i hasn't been too troublesome.

I am able to drive the car for months on end during cooler weather and most of the time during very hot weather without issue.

But every once in a while I will park the car after driving it on a hot day only to come outside later and find the ground wet under the left front side of the radiator/car and my low coolant light come on (rightfully as the coolant is low). After that I fill up the reservior to about half full and I am good to go for another X months.

I am always taking the cap off and seeing if the tank level is dropping and it doesn't. It has always been one day the tank is half+ full, the next ground is wet and the tank is nearly empty. In fact I just checked the coolant level yesterday as it has been pretty hot the past week around here - it was half full.


It appears like pressure is building in the system a relief valve is blowing off. I would think/presume that the pressure cap on the tank would be blowing any excess pressure off.

Is there a pressure relief valve on the left front side of the radiator somewhere?

Any thoughts????? I am a bit befuddled..... :icon_shrug:

There is "apparently" a plastic expansion tank there, connected by hoses to other parts of the system. It has a bleeder valve and a "maybe" a pressure cap/valve. If any of the hoses, nipples or the tank itself are iffy, you can get a intermittent leak based upon expansion of the parts.

I was just looking at it with the car fully warmed up and I can't see a thing. The hoses in that area are in good shape because I replaced the upper hose and the "water distribution pipe" several years back.

Nothing is visibly leaking.

The only thing I can think of is that drain screw at the bottom of the radiator on that side.

Guess I will try and take that out and teflon tape it or something...

What is the puddle? Is it water or anti freeze? There is condensation from the AC that leaves puddles under the car...

Definitely anti-freeze. The coolant tank is drained almost all the way down with the low coolant light on after this event.

Is it the Norma hose connector leaking?

I have read that there is an overflow tank down in front of the left front wheel that collects coolant from the header tank when is overflows and supposedly coolant gets sucked back into the header tank when the coolant cools off and contracts. Maybe this tank is leaking. I don't have any first-hand knowledge because I've never really needed to look, but I've seen posts on this before.

There is no obvious tank. The 2 plastic hoses that go to the "header" tank plug right into the radiator.

From JTIS -
Coolant Header and Recovery Tanks
A recovery system comprising the header tank and a recovery
tank is fitted. The recovery tank is located in front of the
left hand front wheel arch liner.The header tank provides
the cooling system filling point and carries the coolant
level sensor. The pressure cap allows controlled release of
coolant to the recovery tank during normal operation.The
recovery tank accommodates the expansion of the system
coolant during normal operation. On engine cool-down, the
coolant contracts and is returned to the main system.

I believe the hose is under the header tank.

hmmmm.... I will check JTIS tonight.

The in "front of the left hand front wheel arch liner". I am not exactly sure where that is....

Ron, I had some time on my hands, so I looked around a little on Alldata. The hose to the recovery tank would not be the one on the bottom - what was I thinking ? There are two hoses coming out of the front of the header tank and they cross each other. The one on the LH side goes over (or under) the other goes to the engine and then to the radiator. The one on the RH side goes to the recovery tank.

Thanks... I traced it down and found that recovery tank. I never knew it was there!

I am wondering if it is over flowing and/or not sucking coolant back into the system when it expands.

I poured some water in it to see if it was leaking and nothing yet.

With the engine completely cool, should I just suck it dry?

Anyone have any troubleshooting tips?

marked. I am interested in what you find out about your leak.

The 'atmospheric catchment tank' (as it is called) has a round hole in the side of it a few inches from the bottom to keep the level from becoming too high. If the coolant cap is faulty or the engine is actually running hot then the tank will overfill and dump coolant on the ground. The black plastic 'overflow' hose from the coolant reservoir must be inserted into the catchment tank deep enough for the fluid to be drawn back in when the engine cools enough and a slight vacuum is formed. If the black tube is pulled from the tank you will 'suck air' and the system will be low!!!!!!!!!!!!!!!

Make sure the hose is pushed in far enough and the cap is operating properly.

You might replace the cap anyway as cheap insurance.

When ever I top up an XJ8 cooling system I always fill it to the top, place my palm over the top of the reservoir and squeeze one of the radiator hoses to displace some coolant into the catchment tank in case it is low. If some spills on the floor then I know it is FULL.

bob gauff

In the last few days there was a thread for a very similar problem.

It turns out in that case, that the two hoses at the header tank were transposed.

It is easy to get them on wrong, since they cross over one another.

I've got an intermittent leak too...

Mine is the (new) waterpump bearing seal. It comes and goes at will. I've bought a pressure tester and left it on for numerous days and nights never getting a drip.

Recently I went 3000 miles without adding coolant and no antifreeze smell outside of the car.

However, today I got out of the car and that all to familiar smell was present. One of these days I'm going to get around to changing that pump.....

Just an update.... I managed to catch the Jag "in the act" right after I parked it I came back and it was puking coolant all over my garage.

The coolant in the overflow tank (near the left front wheel well) is boiling! Or steam is coming from the engine coolant causing it to boil. This is happening after the Jag is parked and turned off. I've never had this happen while driving the car. I actually started the car on while it was boiling and the temperature gauge was normal... had the low coolant light on though :-)

So I will go about checking that I have the right mix of coolant to water and I will probably replace the thermostat also.

Weird......

The coolant in the reservoir is not 'boiling', it is the coolant in the engine that is. Does you radiator fan run for a few seconds to half a minute after shutdown? Temp sensor/fan relays.

Might also be a thermostat issue.

I don't think my fan(s) run after I turn the engine off. Though I do know they are working, as I just tuned up my A/C.

The coolant in the reservoir is bubbling/boiling, I personally witnessed it (and heard it). That is either due to steam "blowing" into it or the coolant is hot enough to boil in that tank.

Gonna look at replacing the thermostat... I went to autozone and they charged $40 for it! I said no thanks, I am going to shop around. I hope it is not that expensive for a stupid T-stat.