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Old 6th January 2011, 23:50   #12
Robson Rover Repair
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Default CHAPTER 10 - Overview and common faults for the V6 petrol engines

KV6 Buyers guide / problems, costs and general engine information overview

This guide covers the ESSENTIAL issues with KV6 engine in 2.0 150, 2.5 160, 2.5 177 2.5 180 and 2.5 190 outputs as the issues with them are all common regardless of power output or capacity size.

A history of the KV6

First introduced into the Rover 800 series the engine was designed and developed by Rover at Longbridge to replace the Honda 2.7l V6 engine which was about to become non-compliant with tightening emissions legislation.

The original unit was designed for low volume production and hand built but was later significantly redesigned to fit into the smaller Rover 75's bonnet, although performance remained similar and you could almost call them two separate engines.

At introduction, the engine enjoyed considerable technological advancement compared with its competition, most notably being the lightest and shortest v6 in its class. It has fully automatically tensioned timing drive belts and adaptive Siemens EMS2000 engine management. The fuelling and ignition timing are constantly varied to match the load on the engine to improve refinement.

The engine boasts Variable Geometry Induction, whereby air induction pipe lengths vary to optimize engine torque in response to different engine and road speeds (commonly refereed to as the inlet manifold and VIS motors), aiding refinement and efficiency. Although it bears the name of K Series, the engine has almost no components in common with the 4 cylinder version.

The V6 engine is fitted with four overhead camshafts driven by synchronous tooth belts. It has a single, long, serpentine belt at the front driving the inlet cams and also the coolant pump. The exhaust cams are driven by short link belts driven from the ends of the inlet cams at the rear of the engine. The system was a joint development between Dayco (belt supplier) and Rover. The rear link belts do not incorporate any tensioning device. Belt tension is maintained by very careful control of belt length and the pulley pair is pre-tensioned during fitting. The front belt drive is tensioned by a spring loaded tensioner pulley incorporating a hydraulic damping element.

An unusual feature of this system is that it incorporates "floating" inlet cam drive pulleys that are not directly keyed to the shafts. This means that special setting tools are required to establish the cam timing before the pulley fixings are tightened. This requirement is the result of the complexity of the cam drive train.

In addition to the length and thickness tolerance of the belts, the accuracy of the cam timing is also affected by the positional and diameter tolerance of each pulley and the thickness of each major engine casting. The result is that the required degree of timing accuracy could not otherwise be maintained and typically why the cost for the timing belts on the KV6 is so high.

One of the most immediately noticeable features of the KV6 is its distinctive, quietly growling engine note. Infact when MG-Rover when racing with the 2.0 ZS touring car, many commented n the engine having the most fantastic sound in touring cars since the days of the Ford RS500.

The difference in the 2.5 V6 160/180/190 power levels explained

Three "core" versions of the 2.5 quad-cam KV6 engine are offered in the range (the 2.0 24v V6 150 in Rover 75 only). For the ZT only 180 & 190 2.5-litre models, several special features have been engineered to achieve the enhanced power output and drive ability from these engines. The 190 V6 has 190Ps, and increased torque of 245Nm.

Note there are changes between the ZT 180 V6 auto, over the 2.5 V6 180 models used in the Rover 75 and MG ZT 180.

Beginning with the induction system, the ZT 190 air cleaner has an 80mm diameter intake duct in place of a 70mm duct, and a new intake diffuser. This provides a smoother airflow with less than half the usual pressure drop; it has also been tuned for a more sporting induction sound. Internal engine changes include a new inlet cam profile, advancing the inlet valve opening and improved porting.

A further contribution to the performance boost comes from exhaust system on the 190 model, with 60mm diameter pipework in place of 57mm, new low-restriction metal-based starter and main catalysts and a modified rear silencer unit. This silencer has larger-bore internal pipes, twin straight tail pipes and a mechanical valve, which responds to exhaust pressure at around 4500rpm to by-pass the internal baffles.

The ZT 180 & 190 engines have specially designed MG throttle cams and engine ECU software to provide the right sports car feeling of responsiveness to the accelerator pedal, with a deliberate reduction of the normal throttle on/off damping. Also common to both ZT engines is an enhanced cooling system, with 20% greater cooling intake area, improved-flow radiator and top hose configurations and a new plate-type oil/water oil cooler replacing the oil/air heat exchanger.

A note should be made that the MG ZT 2.5 160 V6 is actually a standard Rover 2.5 177 V6 engine but has been deliberately restricted by MG Rover at the time. The difference in restriction is as follows.

1 - Exhaust - The exhaust systems bore diameter from the manifold back has been reduced by several milimeters down to 57mm like the 180 HOWEVER the rear back box on the 160 is much more restricted than the 180 and 190 exhausts.

2 - Induction - The OEM 160 V6 air intake has some "strangling" on the engine. The air intake system has a restricting trumpet in it in the airbox which obviously slows the engine air intake. This can improve the airflow with this simple modfication that I wrote below for removing it.

V6 160 Airbox modification

3 - ECU Engine map - Obviously with the 160, will have a differing remap than the 177 cars. The VIS motors work on ALL V6 models, 2.0 and 2.5. Its the Rover 150/160/177/ & ZT 160/180/190 map that controls their efficiency.

If you can find a willing T4 diagnostic owner whos able to get the car to accept ZCS codes, and get Xpart to recalculate the codes for the car to be a Rover 75 180 (177bhp and it must be a manual otherwise the car will look for the automatic gear box) you can do that however its EXTREMELY TRICKY and most times T4 owners wont cover the work.

Additionally in the future any time the 160 engine is plugged into diagnostics the car will be recognized as a Rover 75 177 V6 if this is done.


Common Problems and Costs

Brace yourself, the KV6 can be a horrifically expensive engine if it goes wrong or has been poorly maintained. Now by horrifically I mean by the price of a second hand car which all our cars are. Few V6 cars will cost more than £6000 now and many are as little as £600 for an early one and below ive listed the reasons why they appear to be such a bargain to the uninformed buyer.

Sticking Throttle in Freezing Weather

A simple fix, but a dangerous one should you find yourself unprepared for it or if your loved one is driving the car. Thanks to a poor design flaw in how air, water and dirt circulates around the engine, you can often find in the colder months your throttle cable will stick when your driving the car due to moisture and dirt freezing.

Now this can be mild and feel like cruise control, or whenever you change gear, cause the car to hit the limiter and rev significantly. I was caught out by this myself on my first ZT and it scared the life out of me at the time as it was snowy weather.

It is actually prevented rather simply. Petroleum Jelly is all you need and some WD40. Open the bonnet and spray the throttle cable, throttle motor mechanism in WD40, let it soak for a bit, and then give the cable and motor a good dollop and smear it around the mechanism and cable etc.

You can actually lift the throttle cable out, as its only held in place with a black square which pops in with little force, which you can use for adjusting the idol of the engine simply by turning it up or down the thread as you need (this is actually handy to make the engine a bit more responsive should you wish to sharpen your throttle response).

Coat the whole area when dry and you will have no problems in the winter months, especially when they where as bad as 2011! Top it up as necessary and job done, and simple and most importantly, safe.

Timing Belts

This is the big one, and often why many KV6 engine cars are scrapped. As mentioned above, the timing system for the engine is very advanced and the servicing of this reflects it.

The belts are ment to be done at 6 years/90000 miles which ever is sooner.

This is a really expensive job sadly, and typically in the region of £500 to £800 depending on what needs replacing including the cost of the kit, which is around £200 to £400 depending on parts and sourcing, and its not something to be taken on light hearted due to the nature of the KV6 engine. However many mechanically competent owners have been giving this a go and advice is in the forum.

A water pump failure for example, means belt replacements and such, so if your getting it done replace everything attached to the belts Ive seen several snapped belts now resulting in engine destruction.

Ive been a victim of the pretensioner failing on my first ZT V6, despite the fact the belts where done prior to my purchase, however they hadn't replaced the pretensioner which damaged my big end but the engine was drivable but the engine was essentially scrap.

A Rover 75 / MG ZT with a KV6 without this work done will sell for various prices, but even with the work done, it doe not often add significant value to the car, so consider this before you complete the work if you plan to sell in the future.

Thermostat

An issue that started to rear its head in the last few years has been the Thermostat housing failing, or the Thermostat failing outright on the KV6 engines.

Sometimes it cracks, or splits or the pipes around it can leak, but the easist way to check is to remove the engine cover using a long socket and look between the "V" of the engine to the left side, there is your thermostat, if that starts to leak it can be a heart ache and left unsorted it will do severe damage to the engine.





Using this image below, you can look under the pipe labeled "3" and you will find the thermostat.



It should be noted that pipe "3" often breaks at the T junction and should be replaced completely, or if your cheap like me, scrape out the inside of the plastic from the three pipes and use a copper T piece from your local B and Q. 22,000 miles later and mines still fine.

Be careful when sourcing a replacement as people mis-sell the KV6 housing as suitable for both Freelander KV6 and 75/ZT KV6 which infact they are not, as the picture below shows. Note the CORRECT housing for our cars will be stamped with "PEM101050" as the part number and cost you around £30 new, or £60 for the complet

A job that you can do yourself, there are guides in the forum and HOW TO section, and should you not wish to, a mechanic would change no more than £100 to complete the job unless Thermostat has done damage, then the headgaskets would be replaced to be on the safe side.

Note this is not the common headgasket failure as like the 1.8 engines, but rather will occur when the thermostat has boiled the engines insides significantly.

When toping up the coolant system, you should use O.A.T coolant, which is pink. The silicate free, organic acid technology (OAT) provides superior engine protection and is compatible with all vehicle manufacturers' colours of OAT coolants.

This was the specification given by Rover and MG-Rover, and Halfords and such sell it. However your Vauxhaul dealership will also sell it 100% pure (to dilute 50:50 yourself) at a much cheaper price.


Inlet Manifold / VIS Motors

The final major issue with the KV6 engine after timing belts and thermostat is "The rattle of death" as some describe it, the rest of us describe it as a failed inlet manifold. The Inlet manifold controls the amount of air being let into the engine to vary to optimize engine torque, without it worknig correctly, the engine will feel very sluggish at all speeds.

This is the section at the top of your KV6 engine and removed looks like this.


Listen for a tappety noise from inlet manifold (black plastic bit at top of engine at rear) which will tell you if you entire manifold need replacing. You may here a small rattle on start up for maybe 15/20 seconds even if engine is cold or warm, that is perfectly normal and should be ignored, however when it continues and sounds like a bag of nails in a washer machine it will be obvious.

A video of the sound from youtube. http://www.youtube.com/watch?v=J31WoRypFxY

These inlet manifolds can not be repaired and much be replaced, it will sound like this if it has failed, sometimes it can sound like the entire engine is dying, but its a simple replacement job that would take a mechanic a few hours.

Replacement can range between £100 from a scrappy to £300-500 new depending where you source it and it is essential that the inlet manifold gasket is replaced and correct sealant else you will hear a slight hissing when the engine is idling after you reassemble.

With regards the VIS motors these can fail due to oil in the actuators of the motors, built up from the engine itself, a bad design flaw sadly. At 3500 rpm there should be a distinct surge in power, notable in 2nd/3rd gear especially, if theres not your VIS motors will need replacing most likely.

Second hand ones are around £30 and are a very easy fix for anyone, a few screws and your flying, literally. The difference to a car without operating VIS motors is significant.

General servicing costs and maintance

So if all of that hasnt scared you off then heres the good news now, assuming you have covered all the regular issues listed then actual maintenance of the KV6 engine is actually quite inexpensive providing you service it when you should.

Depending on usage, a 12,000 mile service is perfectly acceptable, some do around 6000 miles if the car is used less frequently, I myself do my own KV6 every 6 months regardless of millage.

The basic oil filters, engine filters and such are quite cheap and the dearest thing is actually the spark plugs. You must make sure you use IRIDIUM tipped spark plugs, a set of six will cost you around £40 but are good for around 60,000 miles minimum. Access to the rear bank of spark plugs is slightly awkward but not impossible and doesnt require the removal of the inlet manifold.

As mentioned in the Thermostat section, use of the correct coolant is recommended so use O.A.T coolant, which is pink in colour. Save yourself over Halfords prices and buy none-diluted from your local Vauxhaul dealership. 5 litres will cost you about £22 maximum and when you mix it 50:50 gives you 10 litres of coolant.

Various oil grades are required for different power outputs of the KV6, I have listed them with each engine in the specifics below to ensure no confusion arises.

General Engine information

The various technical specifics of each engine is listed below, please use it as a guide, note check the "8th" digit of your cars vin number to confirm your engine size and power output as there are few obvious signs as to which KV6 is fitted.

Last edited by Robson Rover Repair; 16th July 2022 at 13:32..
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