So with my new to me 04 XJR I am having a cooling issue. The temp slowly creeps up when driving on the highway, but at idle it seems to even out. Temps are high though and can get up to 240 before I turn on the heat. I have replaced the temp sensor, thermostat, and the water pump. I tested the thermostat before I put it in so I know that is working. I am starting to think the radiator is plugged but wanted to get some ideas/validation before I dive too deep into it.

The reason why I think it is the radiator is after an hour + drive the radiator is actually cool to the touch. However, both the inlet and outlet hoses are very hot. This makes me believe the rad is partly clogged. I would expect the radiator to be warmer to the touch and not say 90 degrees on the outlet side. Other than that I am not losing any coolant and there are no leaks to speak of. The fan does turn on and is confirmed each time I turn off the car the fan still runs for sometimes up to 5 minutes.

The old thermostat and waterpump did not have any stop leak or any buildup really on them. So I am not sure what the radiator could be clogged with. I am hoping to avoid replacing it as I do not want to mess around with the AC line.

So I am open to ideas as to what to check or look into. I am thinking about soaking the radiator with some dish soap and vinegar for a day or two to see if that frees up whatever is blocked. Worst case I am putting a radiator in it anyway. But I do not want to run any sort of cleaner through the entire engine if I can help it. I have experience with cars and tooling on them, but the cooling system in this is quite different than what I am use to.

 

It certainly sounds as if the radiator is clogged from your description.

I presume the reason you changed the thermostat is because you had the overheating issue beforehand?

Did the previous owner mix coolant types? Did you know of this problem before you bought the car?

 

The PO said the fans would run after the car was off and I didn't think much of it as I have another car that does that and it means it is running normally. Otherwise yes I started to read about the fans running at shutoff and the top suggestion was to replace the thermostat. So I started there and actually I tested the old thermostat and it would not open completely. PO also had the car serviced at a jag dealer and in fact his neighbor worked at the dealer, so I highly doubt coolant colors were mixed. Red was in the car when I bought it and red is what I have been putting in to re-fill after I open the system. Likewise, no sign of gelled coolant when I replaced the WP or the thermostat. With how much the temp gauge is 'dampened' so to speak, I doubt this was a known issue. It actually only moves on the real hot and humid days. I drove it with the temp gauge not moving for almost a month so I am guessing the PO didn't know about it.

As an update too, I cracked the inlet and outlet hoses loose and disconnected them. I poured my cleaning mixture in and am hoping that the power of Dawn will help. When I had the system open before I noted the hoses had a bit of a slime feel to the inside of them. I gonna guess that is maybe what is clogging the radiator as when I ran water through it nothing of note came out.

But of course, this is just my train of thought. I have never worked on a system with an aux pump let alone a SC pump, and various check valves. So I am open to ideas or suggestions. I have the diagram for the cooling system and it is... daunting to say the least. There is stuff going all over the place.

 

You could try running water thru the radiator to see if it flows thru properly? Also see if it flows out of the drain plug hole with force.

 

Be carefull with the radiator. At 15 years old i can tell you the plastic is most likely rotted and brittle. I have replaced a few this year and mine im sure will be soon too(04vdp w 191k) if you see brown coloration around the top hose the plastic is done. Make sure there a no nest, debris etc between the rad and other cooler in front by removing the radiator to bumper cover and looking between, blew , vacuum or wash out whatever works best

 

Any other early indications of the radiator needing replaced???

Am planning on rebuilding both cars alternators when weather cools down.

Just as preventive maintenance, both have over a hundred thousand miles on them.

Will look at the starters, but from what i read they don't fail very often.

Tapping them will get you a few extra starts, to get home.

An alternator, or radiator failure, on the road, an hour or more from home.

Is a lot more than just another thing, to fix when i get time.

Stranded on the road anywhere, is EXPENSIVE!!!!!

 

Water seems to flow through ok. But I am not sure what the normal flow rate is as I can't say I do this too often. However, my cleaning solution seemed to have freed up a bunch of gunk. A lot of scale and calcium buildup came out of the radiator. So I am wondering if one of the last coolant changes did not use distilled water and instead water from maybe a hose or similar.

Either way I have it soaking another night. I don't want to burn a hole through the radiator but again worst case I will just put a new one in now and not the winter or spring. I will probably used some compressed air tomorrow also to see if I can help move things along so to speak. At least I can tell after basically a drive to work if it is fixed.

Oh yea the rad is toast. I already chipped off a piece of the plastic hose line. But my goal is to basically get the rad clean and I will end up replacing it this winter or spring. I just want to enjoy it for the rest of the summer or fall. I did already clean the front of the rad. It was pretty filthy.

Honestly that is the only sign. The fan appears to run just fine and so is the water pump. I saw a post someone made and said their WP pulley was glazed over and all they did was scuff it up and it solved their overheating issue. Mine feels fine and I mean the WP is working. Really it is the rubber on the belt that grips and drives the pulley.

All the other pieces of the car work great with the exception of the air pump which I am guessing probably needs a rebuild. So I have that kit on order but that is going to go on the winter project pile along with the front brakes. The PO did say that the front calipers may need to be rebuilt and already provided the parts for it, but did not really state why other than the rotors are warped. But as I have the parts I will probably do them.

Also speaking of starters, fun fact with Cadillac is the starter is in the valley of the V8 (referring to the NorthStar engine) and while it is a slight pain to replace, the lifespan is extended quite a bit as it does not get hit with the elements and salt. Much like I assume the Jag. I am guessing it is on the bottom of the car but have not looked that closely yet. With the belly pan the underside of the engine looks real clean. I almost feel bad I didn't drop the pan down before I started draining some coolant.

 

Sorry to bump an old-ish thread, but I hate finding posts that leave issues unresolved, so I always try to make sure I update mine:

So I replaced the radiator on an 04 XJR. Sucked. Hardcore. I did not have to disconnect the AC. I had some prybars that I used to get enough give on the AC condenser to give me room. However, I could not get the bolts that bolt the radiator to the condenser and the SC rad back together. So after hours of fighting it, I just ziptied it. I didn't want to, but I feel like I had to. If I had a lift I probably could have gotten it.

Other thing to note is to pull out the fan, disconnect the connectors on the bottom pass. side instead of trying to do what I did and pulling all the connectors from the fan only to find out the fan doesn't have a pin connector that you can unplug.

Also, I did crack the old radiator open to verify I didn't waste my time. The old one had some form of white residue that didn't feel sticky so to speak, but almost like a real fine sand. I can only guess it is either from using impure water during a coolant mix, or is actually the silicate that separated from the coolant from possibly being too old. The water pump and the thermostat showed no signs of a stop leak, so I do not think it was that. However, the heater-core which also has very fine coolant passages does not appear to be clogged, as the interior heats up fine. So that part I am not 100% sure on. However, the car is now fixed. Hot weather with the AC on I run between 205 and 215. AC off I run between 208 and 213. I presume this is because the AC auto turns the fan on low speed. The car has not got to 220 or above since the replacement, so I am calling it fixed. I know some people have mentioned that 210 and below is the range, but I personally have no data to go off of for this car as this issue was present when I bought it.

So mission accomplished I guess.

Next up is front brakes and rebuilding the air suspension...

 

Glad your back on the road with all concerned staying nice and cool.

 

Where did you pick up the radiator?

 

Oat or for europe G12+ silica free is the coolant that should be used , as water only use distilled water please even if you have a leak.
white sand in the radiator might be aluminum oxide. Some of us know what it looks like when moving the side mirrors on older xj's white powder falling on the paint.
easist exchange of coolant can be done over the expansion tank with running hot engine ( no bleeding needed). Stop the hot engine , open up the lid carefully to release pressure , unplug the hose on top of the expansion tank do not damage the tiny nipple , shove a tinier transparent hose into the hose to purge any coolant coming from the engine into a 5 liter container or a bucket . Have 10 liter of distilled water ready to fill up the expansion tank gradually while the coolant is being pushed out . When done with the destilled water continue with filling with 5 liter or more of coolant OAT / G12+
this is what can happen if Coolant is wrong or in the circuit for way to long and naturally tap water can do damage too... this is the heater core of an xj6 2003 with 142.000km no heat inside cabin