Holden Wagon Range

It’s nice to see that some of us are still recycling and keeping old cars on the road. Your question was a hot topic back in the mid-1980s when unleaded petrol (ULP) was being mandated for all new cars. The issue was that older car engines were designed to run on fuel with a small amount of lead in it to help protect (mainly) the valve seats (hence, leaded petrol). The lead also helped prevent detonation inside the engine by raising the petrol’s octane rating. Without this lead, the engine could wear out prematurely, and it was something that owners of existing cars were very worried about.

The ultimate solution for older engine was the installation of what’s called hardened valve seats which, as the name suggests are valve seats in the cylinder head that were physically harder and would cope with the lack of lead. Since your car is older than most people reading this, you may find that it’s on its second, third or even fourth engine and, in that time, may have been fitted with hardened valve seats. Knowing the history of the engine would be very helpful.

But if you don’t have that information, the best advice is to run it on 95-octane fuel (for the octane rating to prevent detonation) as well as a lead-replacement additive to protect the valve seats. This additive can be added to the tank when you fill up, or as a permanent kit fitted under the bonnet that drips a small amount of additive into the engine as it runs. The Valve-Saver brand was a popular make of this type of kit back in the day.

When the time comes to perform work on the cylinder head, think about having the valve seats replaced with hardened ones, at which point you can forget about the lead-replacement additive.

The first conclusion many mechanics will arrive at is that the engine’s head gasket has blown, allowing the oil and coolant to mix. Have a look at the dipstick. If the engine oil is milky, then this is a very real possibility. Perhaps when the cylinder head was replaced, the gasket has not sealed properly.

But if the oil cooler was replaced because it was leaking into the radiator (which is pretty common) then you might find that the oil you’re still seeing is just residual oil from the previous failure, and not a problem at all. Even so, it would be wise to replace the coolant and flush the system to try to eradicate all traces of the old oil.

A workshop can perform a chemical-based test to see if the head gasket is leaking. It’s worth the relatively small cost to rule this out and begin to look elsewhere.

You were on a pretty good bet that the problem was a case of warped brake rotors, but it seems new rotors have not fixed the problem. In which case, you need to start looking deeper into the suspension and front end of the car. There could be a worn bush or ball-joint, or perhaps something in the steering needs tightening or replacing. A slightly bent stub axle could also cause this. Make a note of whether it happens in corners (left or right) under light or heavy braking or even when accelerating. This information will help a mechanic diagnose the problem accurately.

But don’t ignore this as the problem will only get worse as whatever is worn becomes more worn. Eventually, you’ll have a car that shudders all the time and is unsafe to drive.