Jaguar xk8 - 1998

Evening all,

The heater hose that runs from the thermostat area, under the inlet manifold and then to the octopus pipes? at the rear engine, split the other day just where it joins the plastic pipe at the front of the engine next to the thermostat.

To save hassle and to get me home i cut off 2" of the pipe and then re-attached the pipe back up, basically cutting out the split section. However, once the car got up to temperature i was watching under the bonnet and the hose literally let go, burst and split again, showering the engine and front wings and beyond with coolant as it was a fair pressure. The car heater was off.

Should it be under that much pressure? If so, then maybe to whole hose is a weak link and needs to be replaced but i wouldn't have thought that pipe would be under much pressure. Not had any overheating issues in last month i've owned it and starts cold and drives lovely. Heater worked before.

Any help is appreciated

 

Welcome to the forum taylor6632,

That certainly sounds like excessive pressure in the cooling system finding the weakest link. Usual culprits are either a sticking thermostat or a failing water pump although a blown head gasket is also a possibility.

When you get a minute, please follow this link New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum to the New Member Area - Intro a MUST forum and post some info about yourself and your vehicle for all members to see. In return you'll get a proper welcome and some useful advice about posting to the forum.

Graham

 

ah was hoping the head gasket words wouldn't come up. haha. Really hope its not that after less than a month of owning it!

Last owner renewed the thermostat housing for the aluminium one and would hope, also renewed the thermostat but its worth me looking. Hadn't had any issues up until i could smell coolant recently, found the leak after a week or so and now its just exploding with the pressure. I was going to change the heater feed hose for a new one to eliminate that its a weak part, but then something else could go.

Its had all new pipes around back, octopus ones, new rad and by looks, fairly new top/bottom hoses.

I'll head over the new members area now!
Thank you.

 

Your post indicated the car is 1998 model. These were known to have the Black Impeller that disintegrates and move no coolant. There was no mention of water pump replacement. Perhaps the water pump is culprit rather than the Head gasket? Hope so.

 

Forgive my ignorance, but if it wasn't pumping coolant wouldn't it overheat? And wouldn't there be no flow out of the leaking area when running?

I'm not sure what happens to the cooling system if the pumps on its way out so correct me if I'm wrong

 

What makes you so certain it's not overheating? The temperature gauge is NOT a reliable indication. It doesn't move from 'normal' until the engine is seriously overheating.

Have a search for threads on 'Realgauge' for the truth about the temperature gauge.

Graham

 

I would echo what has been said before. Double check that the water is actually being moved around, i.e. water pump. If in doubt, just change it, they are not that expensive.

If work has been done recently, check the coolant fluid. Mixing incompatible types leads to gelling. If in doubt, just flush everything, and go with whatever Jaguar specified.

Also, I believe the thermostat has to put put in the right way (is it with the giggle pin on top, or the bottom?), otherwise, it overheats. Same if the thermostat is actually missing, however counter-intuitive that is.

Last, as a last resort, there are kits to detect exhaust gas in engine coolant. If positive, then a head gasket is likely the culprit.

Best of luck, keep us posted.

 

thank you, i'll try the water pump replacement first as i don't think it actually has been circulating fast enough from other posts i've now read. What damage may have been caused should the pump be failing or failed?

 

The Jaguar V8 is a 'low volume, high flow rate' cooling system. The N/A model is only 9.5 litres capacity and the S/C is 11 litres.

This low volume assists rapid warm up from cold and is an efficient system when working properly. The problem comes if flow is restricted or there is coolant loss. Engine temperature rises very quickly and serious damage can occur. As several members can unfortunately testify, overheating is an engine killer.

It sounds like you've been lucky this time but the issue needs investigating and resolving before using the vehicle. If there's still any of the original hoses on a 1998 then they need replacing. As has already been mentioned, the early water pumps had an impeller weakness and even a recent thermostat could have failed (partially) closed.

The two regular issues on early XK8/XKR's are cooling and 'sealed for life' tranmissions. Get these out of the way and you can enjoy many troublefree miles.

Graham

 

Cheers, I have ordered up a new water pump and hose for that section. All back heater hoses have been done. I'll fit them this weekend hopefully and be back one the road.

The gearbox has been done a few months ago, new filters fluid etc by a jag garage.

I've not driven it much, nor hard in the month i've owned it but its done some long (ish) journeys for the UK, haha, i know 80+ miles in America is popping to the shops. Never showed signs of overheating so hopefully i've caught the pump before it failed and no terminal engine damage has been done

 

Those are the pictures of it just after it let go. You can see the split in the pipe where it joins the plastic water splitter (bakelite?) on the hose that runs off and down under the intake manifold. Hope that solves any confusion as to which pipe it is that split

 

ALSO, should the tiny length of hose linking thermostat hosing to the plastic water splitter be that bulging? You can see what i mean in the bottom picture.

 

Definitely not. Looks ready to let go at any moment. I wonder why it wasn't replaced when the ally thermostat tower was fitted. Even the OEM part isn't that expensive as Jaguar spares go.

Consider replacing the outlet (crossover pipe - what your split hose is connected to) 'while you're in there'. That isn't horribly expensive either. See marvin miller's earlier post on the result when that fails.

Mike

 

Definitely NOT. Here's my 2001 XK8:

OLD BY-PASS HOSE


NEW BY-PASS HOSE


A new hose is a very tight fit and doesn't bulge at all with the engine up to temperature.

Graham

 

So i've stripped it down this evening. Got brand new looking water pump with metal impeller, brand new looking thermostat (probably replaced when last owner did stat tower, few months ago). Coolant once drained looked clear and healthy.

I've no idea why i've got so much pressure in the system and hoses are bulging and bursting. I'll order up a new bypass hose as that one is well and truly had it!

 

I changed the coolant reservoir recently as the level sensor was broken and coolant was leaking out. Could it be as simple as the pressure cap on the new tank is bad? I'm clutching at straws for it not to be the head gasket!

 

Hmm, normally, the pressure should be regulated by the cap on the expansion tank near the firewall. Maybe you should check it, and consider a new cap as well.

Are the fans coming on at all during any of this overheating?

Also, check the engine oil for any sign of engine coolant. If there is, it would be an unfortunate sign towards the head gasket.

Using your detective skills, is there a scenario where the previous owner threw a bunch of parts at a problem, did not solve it, and put the car up for sale?

 

Fans would kick in and out as i'd expect when stationary/moving. Engine oil looks clean and golden brown, been checking it regularly just in case.

Could be that scenario as he had it less than a year, but he had a v8 cobra kit car which he had completed and gone through the IVA so wanted that on the road instead of the jag. I'm maybe a bit trusting, who knows, but he seemed genuine. He replaced all discs and pads, put new stainless sport exhaust on, new rad and oil cooler as was leaking into gearbox, new gearbox service, engine service and bought loads of cosmetic things to replace the little niggles on it (aerial cable sticking, mirror glass damaged etc). I'd think that odd to do all that extra work if this was a problem during his ownership....maybe. Plenty of con artists about nowadays though!

 

I'm not sure of my facts here and I don't think it applies to your car but .............. on early cars, there are two small pipes from the coolant reservoir. Later cars have one. Later coolant reservoirs have two "stubs" but one is blanked off.
If you have two pipes check that they are :
1. Connected the right way round.
2. One is NOT connected to a blanked off stub.


More info here :


http://www.jagrepair.com/images/TSB/XK8/303-15.pdf