steeringpump faillure

squadragrunn
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steeringpump faillure

Post by squadragrunn »

hi guys, i'm using a steeringpump from a 164 in combination with a rack from a 75
now i have blown up nr3 pump due to heat build up in the oil, i'm fed up with it
does anybody know what the source of the problem could be? i have installed an extra coolingspiral, so it has two, nevertheless after 15min of driving, things get pearshaped
is the rack obstructed ore something or is it the combo and should i use a 75 pump (or rather lump) the powersteering works well when cold.......help!!! :wall:
-charles-
gtv6 3.0 24v, 164qv 24v, maserati biturbo 2.8 evo, mb 500se, zzr1100d

squadragrunn
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Re: steeringpump faillure

Post by squadragrunn »

solved
164 pumps work at 100bar, rack needs more, 75pump works at 130bar, so i had to replace the pump
-charles-
gtv6 3.0 24v, 164qv 24v, maserati biturbo 2.8 evo, mb 500se, zzr1100d

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killaz
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Re: steeringpump faillure

Post by killaz »

I have found very good article on alfabb related to this issue. I drive 164 pump/75 rack combo too and buried two pumps already. Now I'm planning to modify 164 pump internally to reduce flow since it seems that too much flow is guilty for building high temperatures... If anybody did this mod, please share. I will post some pictures and observations as I go on.
This will be last attempt in trying to drive with ps, if it fails again I'll convert it to manual...
As posted previously, I have used a 164 PS pump mounted down low on the right hand side of the engine. This is for two reasons: One is the placement of the PS fluid reservoir up on the RHS rear of the engine bay (i.e. little room on the left side of the engine bay unless you hang it out in no man’s land near the exhaust); the other is using a nice light, more modern and compact pump. Additionally, the old 75 pumps can be a bit problematic to seal up once they start leaking. The odd thing is that other people seem to have used 164 pumps and not come across this issue…

As described before, on initial test runs I had very annoying hissing coming from the rack coming up the column into the cabin. The system made no noise until the steering wheel was moved even the slightest bit off resting position (even when the car was stationary at idle). Initially, I thought that it was mainly a result of having to have a full set of new hoses made to suit the new routing in the engine bay (and not being aware of the anti-noise restrictor in the pump to pressure line…. the new hose did not have one): the 164 hose has a restrictor of approximately 3 mm. The 75 supply hose also has a restrictor, but I do not know its size .

I made a 3 mm restrictor and inserted it into the supply hose and yes, it made a difference but did not completely resolve the issue. I tried a few different sizes (all smaller) but could not eliminate the noise. I also noticed the pump started to have significant heat build-up after short drives: a clear sign that the pump had excessive load on it.

So I sat down and nutted this problem out with the limited information I could get on the web and examining the components. Eventually, using the diagram attached that shows the basic way PS works with modern vane type pumps, I worked it out.

My understanding is (I am happy to be corrected):
There are fundamental functional differences between the PS pump in a 75 and that in a 164. Besides that the 75 pump is a radial piston and the 164 is a vane type, the 75 pump supplies a constant flow to outlet of the pump (it has constant residual internal pressure and a relief valve set at the maximum pressure) whereas the 164 (vane type) pumps varies the pressure and volume depending on the load required up to a pre-set maximum pressure. In this way, my belief is that the 164 pump will have lower parasitic losses while there is no demand from the rack.

The 75 pump supplies constant flow out of the pump to the rack through a 1.5 mm orifice (this is in the outlet banjo bolt on the pressure side of the 75 pump): this flow is quite low in comparison to that in the 164… The valve body in the rack them directs the fluid (if needed to the appropriate side of the rack) or to be recirculated back to the reservoir.

Under normal circumstances, the 164 pump has higher flow (but lower pressure) to the rack. This is done by an internal flow valve that recirculates the fluid back into the pump’s inlet side. When there is a pressure demand on the rack (vehicle is steered and fluid flow drops through the valve body and is directed into the appropriate side of the rack), the pressure in the supply line to the valve body increases. There is a signal port into the back of the flow valve that will then increase the output pressure to the rack (to the point where the pressure relief valve opens). This creates a self-regulating circuit where the pump only will output the pressure required of it (thus being less energy sapping).

There must be some difference in the valve body on the racks of the 75 and the 164 to cope with the difference in the pump characteristics…. The 75 rack just can’t cope with the volume of the 164 pump: thus the hiss.

By studying the attached diagram (it should be noted that this diagram is for speed sensitive Servotronic power steering and not truly representative of a 164 power steering system) you can start to understand the workings. Of note is the flow control/pressure relief valve system in the pump. The lower restrictor controls the actual flow to the rack (in a 164 it is hard to measure but probably around 3.0 - 3.5 mm) while the upper is the signal to the back of the valve (about 0.5 mm) to control the pressure. Should there be a restrictor downstream of the pump smaller than the main one in the pump, the pump will carry undue load. The trick was to calibrate the 164 pump to match the 75 rack: this was done by inserting a restrictor (1.5 mm) in the pump (delivery side of the control valve, upstream of the signal port) to regulate flow to a maximum (for any instantaneous pressure requirements at the rack).

The result is: dead quiet power steering with great weight and low parasitic losses (the pump takes a lot longer to heat up) .

So, the lesson is: you can use a 164 pump on a 75 PS rack, but do not assume it is a straight make a bracket and bolt on exercise….

105gta.
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Re: steeringpump faillure

Post by 105gta. »

Excellent detective work there Killas.
Do you happen to have any pictures of your mods to the pump? I'm assuming it would be the same case for the 156 pump as well.
Ben

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killaz
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Re: steeringpump faillure

Post by killaz »

All the credit goes to a guy which is op (clayton105). I'm about to start this modification and will post pictures... Cheers!

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75evo
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Re: steeringpump faillure

Post by 75evo »

Why not go with electro mechanical unit from a..... Citroen or something? I bought one from the UK and will try that. Needs a bigger alternator though. Less belts and you can mount it anywhere.

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Re: steeringpump faillure

Post by Jim K »

Why is everyone having ps problems? Here in Athens, we take the racks and ps pumps to the ZF service center and they do a great job rebuilding them. Sometimes they may reject some parts as 'worn beyond repair' but fortunately, there are loads of 75's in junkyards! I've had these parts rebuilt in both my 75's. 8)

Jim K.

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75evo
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Re: steeringpump faillure

Post by 75evo »

The pump doesn't ever break. I think because it is German, ZF. The only thing which ever needs replacing are the small seals. Probably Italian made seals.

I fixed mine 13 years ago and it never gave problems again. But I like the idea of electro-mechanical. Stefano Roma on alfabb installed it in his 75 3.2.

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Re: steeringpump faillure

Post by darryl longley »

never had a gtv6 with power steering
In Yorkshire power steering is for girls

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killaz
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Re: steeringpump faillure

Post by killaz »

@Jim: No ZF service center here and original steering pumps are pretty rare here too... Personally, I like the idea of small compact pump such as vane type from AR164.

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Re: steeringpump faillure

Post by Jim K »

Since 1990, all 75 Trofeo models (with 1.6/1.8 engines) had power steering, so no shortage of pumps and racks here.

Jim K.
Last edited by Jim K on Fri Aug 05, 2016 9:39 pm, edited 1 time in total.

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killaz
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Re: steeringpump faillure

Post by killaz »

Good to know, next year for vacation I'll salvage some racks for spare. :D

I've finished pump conversion today. PS pump works really nice, no overheating or strange sounds, tried sharp manuvering left- right-left and no problems with oil starvation. Oil in expansion tank is still and without bubbles. Next test will be on track in september (hopefully).
Attachments
Pressure control valve and orifice. I've decided to modify this pump because orifice is not press fitted. It pops out easy.
Pressure control valve and orifice. I've decided to modify this pump because orifice is not press fitted. It pops out easy.
20160804_135304~2.jpg (92.99 KiB) Viewed 5495 times
Fabricated orifice for less flow (left), one hole 2mm diameter. Original orifice has three holes: 3mm, 1.5mm, 1.5mm.
Fabricated orifice for less flow (left), one hole 2mm diameter. Original orifice has three holes: 3mm, 1.5mm, 1.5mm.
20160804_171003~2.jpg (119.09 KiB) Viewed 5495 times
Friend says that this pump belongs to Alfa Romeo 33...
Friend says that this pump belongs to Alfa Romeo 33...
20160805_150943~2.jpg (81.04 KiB) Viewed 5495 times

105gta.
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Re: steeringpump faillure

Post by 105gta. »

Hi Killaz, just curious the holes in the restrictive do they go right through as in one hole either side or just one hole on one side of the brass piece?

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killaz
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Re: steeringpump faillure

Post by killaz »

Hi! I'm not sure if I understand you, but I'll try to explain: In original restriction for this pump; there are three holes on sides that are connected with main hole which leads to supply line. On new restriction, I made only one smaller diameter hole if compared with factory unit. It would be cool to check and compare parasitic losses with this setup? :)

I was driving track day with new setup and no problems (sunny day 25 degree C), lots of charging 5000 rpm-7200 rpm. Works perfect but for hot days I'll mount aditional cooling tank to keep oil in better temp range.

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Re: steeringpump faillure

Post by MD »

darryl longley wrote:never had a gtv6 with power steering
In Yorkshire power steering is for girls
darryl you da man !! Give that man a beer!

I don't know how many times I've had this topic in discussion but there is always one out there that wants to do this.

If you have grown up driving front wheel drive cars, you are probably used to power steering and believe it is the norm. You think nothing of it. All cars should have power steering.

That's a total load of crock shit. Well, unless you have a 5 litre cast iron boat anchor living under the bonnet and ten inch wide wheels you may need it.JK needs it in his 75 cause he's an old fart who gets a lending hand to brush his teeth due to the weight of the brush. He was toying with the idea of going mucho and ripping it out but realised there would be a better resale if it was left original. :D

A rear wheel drive car like the GTV6 does not need power steering. Never did, never will in its usual guise. Nobody seems to pay any attention to the feedback issue of a manual rack. Nor the speed with which it responds and the lack of speed response from a power rack. NO OIL PUMP POWERED STEERING RACK WILL/CAN EVER EQUAL THAT.

If you have a pair of chicken wing arms and you must have power assist, go the electric tack on but don't do the oil job. You are ruining the best steering set up you can get for road cars.

darryl. I am glad to see you get it mate.
Transaxle Alfas Haul More Arse

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