Consistently failing hose

[Mr MXT]

I have had an ongoing problem with the coolant hose that runs from the turbo to the heater matrix. Firstly the rubber hose split completely while the car was on a rolling road.



We did some reworking and replaced the old rubber hose with a silcone one:



I then had issues with a small leak at the heater matrix end. I'm aware the heater matrix pipes are very soft so if you use a jubilee clip it can't go on too tight. Becuase we couldnt go too tight, the hose popped off at the heater matrix end a couple of times causing some major brown trouser moments (Evaporating coolant looks a lot like smoke when it is billowing out from uder the bonnet!!)

This was fixed by double jubilee clips at the heater matrix end and clipping the hose onto the edge of the block to minimise movement (apologies for wrong picture angle)



All has been fine for a good few months, but now today the same hose has failed but this time at the turbo end! The turbo was too hot to be able to get the hose off so I'm yet to determine how it has failed exactly, but fail it has.

Any ideas what could cause the same hose to fail over and over again?

I'm running a 1.1 bar rad cap, but wouldnt have thought that was a major issue as the standard mx5 cap is 0.9bar I believe?

I'm planning on swapping it for a steel braided hose with good quality aeroquip fittings but I'd still like to know whats causing the issue...

[TheEnd]

Would that be the normal routing? to the matrix?

I'd take a guess at the coolant boiling and the pressure popping it off.

Is it heading turbo>matrix, or matrix>turbo?

[Mr MXT]

TheEnd said:

Would that be the normal routing? to the matrix?

I'd take a guess at the coolant boiling and the pressure popping it off.

Is it heading turbo>matrix, or matrix>turbo?

I don't know My term "we" was the royal we!

ETA - If the coolant was boiling would I be experiencing heater problems? The heater seems to be working as normal.

Also, perhaps apart from the time on the rollers, when the hose has failed the car hasn't been under particular stress or running a high temp. Today for example, the car had onyl just got up to temp.

Edited by Mr MXT on Saturday 5th March 22:47

[Pumaracing]

You're routing the hose up and back down again higher than anything else in the system. It's going to have an air pocket in it.

[Cooky]

Agree with the air pocket issue, also the silicone hose isn't always the best option. Try using SAE100 R6 nitrile, it is thin wall high pressure textile braided hose and will work up to 120 C.
It's available from your local Hydraulic Hose distributor and you can clamp it on with a decent jubilee or mikalor clip.

[Mr2Mike]

What is the failure mode, where does it split? In the middle or at the point it's been clamped? Is it possible the barbed fitting on the turbo has sharp edges?

[cptsideways]

Hard pipe it! at least where its near the turbo.

[JontyR]

cptsideways said:

Hard pipe it! at least where its near the turbo.

+1

You can put a bleed nipple in the top of the pipe also, this will ensure you can remove all air from the system.

[stevieturbo]

Post a picture of the damaged hose. Can't say Ive ever had an issue with a coolant hose that small coming off.

Is it crap hose you are using, or is the hose end covered in oil or something ? Or crap hose clamps ?

Even on smooth bore fixing ends, ie no bead, Ive still never had issue with such a small hose coming off, regardless of usage.

[Mr MXT]

I will get a pic up later. The hose was high, but when we reclipped it as it is now, I think the angle of the pic makes it look more exaggerated.

If there was an airlock in the hose, would it manifest itself in terms of the engine overheating? I haven't suffered from anything like that.

Great idea on the hard pipe and bleed nipple though; I think that is the way forward!

[steveo3002]

have you revved the engine and see if engine movement is tugging on the hose?

sounds a bit strange if the hose was a proper snug fit

[Mr MXT]

steveo3002 said:

have you revved the engine and see if engine movement is tugging on the hose?

sounds a bit strange if the hose was a proper snug fit

Yep, hardly any movement when revved!

[GavinPearson]

I think that using coolant that has come from the heater is a big no-no, the heater is supposed to get the absolutly hottest coolant from the entire system so it will warm the cabin, and if you aren't using the heater blower the amount of temperature loss to the outlet is minimal. So this won't do anything for the turbo. Bottom line - you need a cooled feed for the turbo that is around the same temperature level as the block water jackets. You also need a volumetric flow rate that is adequate, and heater circuits tend to be restrictive to avoid core erosion. This is not going to be good for the turbo.

This probably is overtemping the hose and causing it to fail. Getting the routing right, using the right material and keeping the system free of air should fix the issues you have.

[eliot]

I was told by turbo technics to use a banjo bolt and get a small length of pipe brazed onto it. This gives you some distance from the turbo, so the hose doesnt get as hot. However I just attached some 8mm hose onto the banjos and have never had a problem.

[cptsideways]

ETA - ignore that post

[Mr MXT]

I've taken consultation from Steve @ 5 speed who has suggested a practical way that it could be rerouted, so I will be doing that I think.

Thanks for the advice guys.

(Incidentally, the car was owned by HKS who installed the turbo kit, you think they'd do it right!)

[Drop Test b3nxj]

Mr MXT said:

I've taken consultation from Steve @ 5 speed who has suggested a practical way that it could be rerouted, so I will be doing that I think.

Thanks for the advice guys.

(Incidentally, the car was owned by HKS who installed the turbo kit, you think they'd do it right!)

the work was done by the guy who owned it in his own time, that fact that he works for HKS is nether here nor there.

[Mr MXT]

Drop Test b3nxj said:

the work was done by the guy who owned it in his own time, that fact that he works for HKS is nether here nor there.

Do you know any of its history? The invoices are direct to HKS?

[Drop Test b3nxj]

Mr MXT said:

Do you know any of its history? The invoices are direct to HKS?

I know a little bit, I know it spent very little time being used and alot of its time being looked after and polished.
what happened to the Rays that were on it?

[Mr MXT]

Drop Test b3nxj said:

I know a little bit, I know it spent very little time being used and alot of its time being looked after and polished.
what happened to the Rays that were on it?

The guy that had it before me swapped them for the 16s. I've seen pictures on the old wheels, I loved them I was tempted to buy another set but in 16s. It is very clean, and low mileage, one of the reasons I bought it.

There is a thread running here if you (or the previous owner) is interested in how the old girl has moved along.

http://www.pistonheads.com/gassing/topic.asp?h=0&a...