I have an 01 low mileage XJ8, USA. Anyhow, every once and a while, this simply tosses a coolant hose off the nipple. So, I have read that:
1. Change the pressure cap. Done.
2. Change the thermostat. Runs fine, temp OK. Not changed.
3. Scuff up the nipple. Get smooth. Done.
4. Check engine mounts. Seem OK.
5. Use new spring hose clamps. Not done. Hmmmm

This has happened about four times in four years and about 8K miles (currently has 56K.) Never while just driving. Always after a shut off or after coming to a stop sign after driving up the mountain. (5,000 feet).

I decided to do what I do on our boat, double clamp the hoses with worm drive hose clamps. Worked good for a while, but just lost one after a half hour drive; car in the garage; off for 15 minutes; walked in to the garage; heard a "pop" and found the hose feeding the left side of the radiator off at the engine. This is the one right in the top middle. Roughed up the nipple and re-installed. Checked the other clamps and they were a bit loose.

So, is there traction to there being a great expansion of plastic nipples vs. alloy? Should I get spring clamps and replace them all? (If I do, I will still double clamp them.)

I obviously have checked the archives, but I'm sure I missed something...
If I had something to offer here, I would post more often, but I'm afraid I don't. This is a weekend car that is a preservation exercise, so she doesn't get much mileage. I am trying to pile some miles on since it has to pass a smog check and the computer was re-set about 600 miles ago, so it won't pass. Smog guy says "drive it more"!

Thanks in advance;

Rick D.

 

I would replace BOTH the Thermostat Tower AND the coolant outlet pipe (crossover pipe).

They are resin and they wear out.

The thermostat tower can be replaced with the aluminum version.

bob

 

OK, I ordered them (in aluminum). So, I see you have cred... what's your take on the hose clamps?
RD

 

Mine came with a new thermostat.
I am not completely clear if / when you renewed yours, but I should change, just for peace of mind.
They do tend to lock up over time.

 

I just ordered the aluminum version on e-bay. It does come with a thermostat.
RD

 

I think you indicated that you ordered a cross over pipe also. That's important as several members had the hose pop off because the plastic pipe was eroded.

The clamps should not be a problem with the plastic parts replaced.

 

Thanks. Any special care when replacing plastic engine parts? I assume the touch on the wrench is delicate.
Rick D.

 

Hi all together,

From my experience I went back to the original spring clamps. When I did the coolant system in the first place, I replaced almost all spring clamps with worm drive clamps. 1 1/2 years later when I had to work on the coolant system again, I experienced that some of the replaced coolant hoses (e.g. the valley hoses) were slightly damaged due to overtightening the worm clamps at the connector pieces. It's quite easy to overtighten worm clamps without noticing it. When installing them for the first time and with the engine cold it looks fine, but when up to temperature and a few month down the road the hose expands and contracts multiple times which pushes the rubber through the small apertures of the worm thread. It didn't cause any leaking after the 1 1/2 years, but the attachment points of the hoses looked quite bad compared to the hoses which had been with the engine for 15 years in the first place.

So I went back for new genuine spring clamps for all the hoses which are difficult to access (valley hoses, all the small hoses at the throttle body, EGR-valve etc.).

In addition to all what I said above you should keep in mind that on SC-cars almost all the connectors are made of aluminium. But with the non-SC cars you'll definitely face the risk of breaking the plastic or resin connectors when unintentionally overtightening the worm clamps.
And last but not least: if a worm clamp comes loose it will stay loose...the spring clamps come with a preload tension and won't ever come loose (except the pressure in the system gets crazy high).

That's just my two pence on the issue of the clamps ;-) And since I have a special pliers for these spring clamps, I lost all frustration and fear of these clamps (which are a PITA to work on if you have just standard pliers at hand).

 

@xjr2014_de
Spot on!

 

Life is easier with both types of hose clamp pliers.

 

Looking @ getting these, when I go back through my whole cooling system.

100 Pcs 10 Sizes Autos Spring Clip Fuel Oil Water Hose Pipe Tube Clamp Fastener

 

Here's what I did : get a cooling system pressure tester (ie, Mityvac), and crank it up to 5 PSI above the pressure rating of the cap. First time I did this, leaks appeared all over the place. Tightened up some clamps, replaced others, a new hose or two, now the system holds 25 PSI.

 

Those spring clamps are actually the better ones when it comes to life, rust, servicability and replacement...

I'll most probably be going that route on the V12 too...

 

The reason spring clamps are used is that they 'self-tighten' as 'cold-flow' occurs over the life of the hose.

bob

 

But do a search on replacing the Thermostat tower. The bolts are tricky to get at, and more difficult to tighten. Lots of threads.

Also make sure your overflow pipes are correctly installed: these are the black hard plastic pipes from the tank to the radiator and to the overflow bottle in the fender: these are frequently misrouted causing higher than normal pressure. They cross over each other: otherwise they are not installed correctly. Again, lots of threads with great drawings.

I used the the screw type radiator hoses after one of mine blew off: being reasonably **** -- as you have to be with cars this old -- I tighten them every month and twice as often when it drops below freezing. Maybe the spring types make this unnecessary, but I wasn't will to take a chance.

 

FWIW, I found these spring hose clamps that appear to be identical to OEM at McMaster-Carr. 1 31/32" (50mm) for what is a reasonable price. Looks to be the right size given a trial fit on the new crossover pipe.
https://www.mcmaster.com/#catalog/123/310/=18gy87o
Also got a cable hose clamp pliers :-) (McMaster Carr, for those who don't know, is a vast on-line hardware and materials supplier.)

I will check other threads re: replacing both the pipe and thermo housing and look on You Tube too. Don't want to do unnecessary work. FYI, I didn't intend to do much work on this car given some other pressing projects (my boat, the other XJ, etc) but am somewhat forced to if I want to keep it since the nearest independent is 50 miles away the prima Donnas up here in the mountains won't touch it.

Having said that, I trouble shot a no-start condition (relay), back up sensor, (used on e-bay), power antenna (cable and mast) and fuel pump (wasn't the fuse!) through assistance from the people contributing their expertise and experience on this site, so once again... THANK YOU.

 

While waiting for the parts to come in, I have been regularly checking the screw-type double clamps I installed on the hoses. I have been shocked to find they are often quite loose, so with that slight survey, I have to conclude that there is something to the notion that constant-tension clamps are needed with plastic hose nipples in hot pressure environments. I wonder if the screw clamps lose their tension by the swelling and contracting? I can't think of another reason.

I have the bypass tube and aluminum thermostat housing (which I painted black). However, I seriously don't like all the nonsense needed to reach the back two bolts of the housing, so I think I'll pass on doing that myself and instead just install an new end with a new 'stat when I do my hoses. I may ask the mechanic to change it over when I take the car in for service in the next month or two.

 

If you know what you can experience, it is actually not a big deal, but I can imagine the stories put you off.

After creating some space around it (crossover-pipe, hoses), I just broke down the plastic tower, it will come off in big junks if you use a vice.

Protect the coolent inlet with a rag to prevent stuff from falling in, and you are fine, 5 min work.

You can then reach the 2 aft bolts, to find 2 possibilities;
- either they come out immediately, and the whole process is really no more than 15 min work,
- or the bolts are a tat too long, in which case you just loosen all 8 or 10 (?) intake housing nuts / bolts a couple of turns, allowing you to lift the housing just enough to get the bolts out, 15 minutes extra....

I bought 4 Allen key bolts for re-install, no issues.

 

OK, the cooling system maintenance is almost done. Like I said before, "don't use screw clamps". I waited for a long time to tackle this because I needed some uninterrupted time which is hard to come by and a little terror in working on this more modern plastic-fantastic engine. I finally found the time and fortitude and found some interesting things. First, THANK YOU for the lead to that cable-operated constant-tension clamp pliers. I don't know how I could have done the job without it. Second, it wasn't nearly as scary as I thought it would be. Third, I wasn't brave enough to tackle the thermostat housing and replace it with the aluminum one I purchased, so I installed a replacement nipple and thermostat. For those who recommended replacing the bypass assembly THANK YOU; it was a mess. The hoses actually looked good; perhaps they were replaced before. Regardless, I purchased new hoses; why wouldn't I?

The thermostat housing hose nipple was eroded around the front; the lip was gone. What causes that (see photo)? There was a break at the front of the hose seat on the bypass. That could have been caused by my adding the screw clamp and over-tightening it. Or, it had been there for a while. The pieces were trapped in front of the thermostat. Finally, I had thought about double-clamping the hoses with the new constant tension clamps, but now I am having second thoughts. What say you? Anyhow, here are some photos. Did I say "THANK YOU" for the guidance?

You can see the breakage on the end of the bypass.


Pieces recovered from the thermo housing.


Chewed up end of the bypass.


Eroded thermostat housing hose nipple.

 

Well, those hose clamps from McMaster Carr are great but just ever so slightly small for sneaking over the hose nipple lips. I tried to order them from Barratt but they are special order. However, I did find what are referred to as constant-pressure clamps that are similar to a screw clamp. They have a spring that keeps a constant tension as the hose and hose nipple expand and contract. I think they should do the job. I went to three auto parts stores and none carries constant tension spring clamps as on the car. And, screw clamps clearly did not work. See this link

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