Yesterday, while visiting my dad my radiator went kaput. I noticed the temp gauge rise quickly and the car wouldn't shift into 4th or 5th. I stopped the car and waited for it to cool down a bit.

I opened the bonnet and noticed that the upper radiator hose was inflated about twice its diameter and a very thin stream was spraying from the radiator plastic next to the connection for the upper radiator hose. Most of the coolant was dumped through the atmospheric recovery bottle.

My dad covered the bill on this, a new radiator and upper radiator hose for $827. The parts arrive on Tuesday and we'll have it installed that very same day.

After the car cooled down, I started it to drive it off of the flat bed truck and into the parking spot. Other than the low coolant warning, the engine seemed alright, with a smooth idle and no smoke. I'm almost sure I don't have a head gasket failure.

I have to ask... I think there's more to this story. What would cause this to happen? A bad thermostat? A bad water pump? I think that if the radiator hose inflated so much, there must have been more pressure than what is normal in the system. Any thoughts?

What about the transmission? Could that have suffered? I was J-gating the car out of a toll when this happened.

 

After a $900 investment in a radiator I think a $25 thermostat, a $70 water pump and the other hoses might be a nice way to finish up since you have to replace the coolant anyway.

Thermostat is most likely but who knows. A blown head gasket will split a radiator also. Been there.

 

Really, the tstat is only 25?

I don't think the blown head gasket would be it. The car presented none of the other symptoms that accompany that. I'll check if I can get the tstat by Tuesday. The water pump seems to me like it might be harder to optain.

 

Anytime an engine overheats it's a good idea to replace the thermostat. Thermostats work by the expansion of a wax pellet and when overheated the wax can be forced past its seal. When that happens the thermostat no longer operates at the temperature it was designed for, if at all.

If the hose was inflated that much I'd be taking a close look at the radiator cap, or in our case, the expansion bottle cap. If it didn't relieve pressure when it was supposed to it would have caused the hose inflation and probably the radiator failure.

Severely blown head gaskets can cause enough combustion leakage into the cooling system that the pressure relief cap can't keep up but that is an extremely odd situation.

Once the cooling system is repaired it's a simple, inexpensive test to check for combustion leakage into the cooling system. Lisle 75500 has been around longer than I have and is available at most parts stores for around $30.

 

Well, how do I know if the cap is bad? I noticed the other day, but wasn't sure, something weird about the cap on my expansion tank. Is the bottom end of it supposed to be completely smooth or should it have an opening?

Mine has an opening that catches the coolant in it. I noticed the other day that once I removed it, the cap would drip a few drops from the inside. I'm not sure if that makes sense. I can't take a picture until Tuesday. The car is at dad's about 3 towns from where I am.

Either way, I need to get my hands on a tstat and I didn't order one.

 

What tools do I need to remove the radiator, the thermostat, the radiator hoses and the oil cooler hose?

 

If you have a basic toolkit with a standard set of metric wrenches and hopefully a socket set, you will be fine. No specialty tools required.

Don't know if they have Harbor Freight in PR or not, but you could buy every tool you needed there for <$50 out the door. I suspect you already have them based on your prior posts.

 

Almost forgot, here's the procedure from the JTIS. It shows disconnecting the AC condenser, but if you loosen it from its bracket you will not need to disconnect it. Takes some dexterity, but saves having to empty and recharge the AC system.

Lots of threads on this, just take your time.

 

Yes, I do own all the required tools... To bad they're at my dorm room.

Maybe my dad or my grandpa have them.

 

So, today we changed the tstat (it was borked), the upper radiator hose and the radiator. However we then realized that the fans aren't working. We are going to send the car to an electromecanic tomorrow to have it checked. My dad has pulled the radiator fan motors from his spare X308 and had them tested. They work, we plan on having them surgically implanted into my car's fan shroud and we will have the electromechanic check why the car burned through three fan fuses this year and have that fixed. It's probably a short circuit.

Hopefully we don't have to buy a new fan shroud.

Also, we noticed that the new radiator has a breather unlike my old one. I could either route a new breather hose to the expansion tank or have the breather plugged. Any thoughts?

 

The Bleed Hose from the Radiator to the Expansion Tank was discontinued early in the life of the XK8. Although the later Expansion Tank appears to have 2 outlets, one is blanked. Your options are:

1. blank the bleed outlet on the replacement radiator (the easier choice)
OR
2. swap the Expansion Tank for the early pattern and fit the second Bleed Hose

Graham

 

I used Graham's option #1 on my radiator replacement.

Took a short piece of heat rated hose, loaded up one end with WaterWeld (JB Weld for water) and a plug, then attached the open end to the radiator with a hose clamp. I dropped it down into the open area pointing to the ground and zip tied it so it would not flop around.

Been on since October of last year without any issues. Best part is you cannot tell it is just a dummy hose.

Cost $0. Used a spare piece of hose and a hose clamp I already had.

 

Alright! What about the X308 XJ VDP fan motors, are those compatible with my fan shroud? Will the electromechanic be able to transplant them for my car's fan motors?

 

Although I've previously owned both X308 and XK8, I've never had reason to directly compare radiator fan sizes.

The shrouds are clearly completely different. Within the shrouds, my impression is the X308 has larger diameter fan assemblies but this may only be because they are mounted diagonally whereas the XK8 fans are parallel.





If he intends to strip the motors from the plastic fans, they both look to be bolted together in the same way:

X308


XK8


It all depends on the motors being exactly the same diameter.

Graham

 

From the looks of that diagram, they seem similarly sized. We'll know in a few hours.

 

A bit of useful news.

Both the fans and the fan motors are interchangeable between the X308 XJs and the XK8. They even have the same wiring harness. The only difference between them is the shroud assembly that houses the fans. The fans and motors can easily be separated from the rest of the assembly.

We still haven't swapped them because today turned into a roadtrip. Hopefully tomorrow this can be finished.

 

The XK8 has one fan of a larger diameter, which requires you to swap motors instead of swapping the entire fan unless you are willing to fit the slightly smaller fan. The other fan is a direct swap.

Separating the motor from the fan is a project in and of its self. I'm still figuring that out. I think I'll use the slightly smaller fan.

Edit, I used both X308 fans and they work flawlessly. That solves my immediate coolant problem.

 

I have had a similar problem with my 98 XK8. First it split the radiator tank,(Kaabooom!). Replaced radiator, tsyat, water pump and all hoses. Then the fill reservoir blew up, (Kaaa BOOOOM!). Replaced the tank and the car would purge most of its coolant as soon as the tstat opened.Then it was too cold to work on the car. It sat for about three months. When I tried to start the battery was dead. new batt installed and it it would crank but not start. Fuel pump had died while sitting. Replaced fuel pump. Now car has been running fine for two weeks with no cooling issues. Go figure?!?!?