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Triumph Stag (1970 - 1977)

Item: Triumph Stag (1970 - 1977)
Rating: 4
Author: Honest John

Last updated 15 March 2017

Buying Guide

Suspension

Check the semi-trailing arm rear suspension. If the car lurch at the rear when you let off the throttle mid-bend, it could be because the splines of the telescopic drive shafts are sticking under power and then freeing in coast. This causes locking followed by a releasing of the rear suspension. This was a lubrication problem Triumph denied the existence of. This lurch is not caused by worn semi-trailing arm bushings.
Several Stag specialists have developed replacement half-shafts that use CV joints that provide articulation, as well as compression and extension without the use of sliding splines. These new half-shafts eliminate the dreaded Triumph Twitch - so check to see if they're fitted.
Test for wear in the suspension bushes by shaking each wheel sideways while a helper applies the brakes. If there is any play, the suspension bushings may need to be replaced. If there is play with the brakes off, then suspect a wheel bearing.

Steering

Power steering leaks may occur, although not to an unusually high degree. Inspect rack gaiters for signs of oil leaks. Type F Automatic Transmission fluid should be used to top up the reservoir.
If the rack leaks, it's best to have it professionally rebuilt.

Bodywork

The Stag isn't known for being particularly bad for rust, but there are areas where corrosion can strike. Look for rust damage in the: -
Floorpan
Front wings (inner and outer)
Rear wing/sill joints
Rear subframe mountings.
Outriggers. Check these areas very carefully, for while replacement panels are available, they are very expensive.
Post-1974 Stags are more susceptible to rust problems than are the earlier models due to the factory switching to a different sheet steel supplier.

Hood

The convertible storage hold can leak, and if the top was not stored correctly, it can be very difficult to erect.
Before the top is lowered into the hold, the rear section must be locked in the vertical position using the two latches provided.
Failure to do this will cause the rear section to become trapped in the hold, although instructions are provided in the owner's manual on how to extract it.

Wheels

Although steel wheels were standard on the Stag, chrome wires have been fitted by some owners.
The usual checks for damaged spokes and worn splines are essential.

Engine

Here's where the Triumph Stag earned its long-lived poor reputation for mechanical fragility. The main area of concern is with its cooling system. Let any car you're looking at idle for 15 minutes, while keeping an eye on the temperature gauge. Check that the radiator is as hot at the bottom as it is at the top. If it's not, there may be problems with coolant circulation. Also check that the thermostat hasn't been removed, and make sure that the oil pressure light is connected.
Stags have a bad reputation for cylinder head warping. The blown gaskets which soon follow can lead to damaged head faces which will need skimming if they are to be rescued. A blown head gasket can also cause engine coolant to seep between the head and the studs.
Electro-chemical reactions between the aluminum head and the steel studs can cause the head studs to seize in place, making head removal almost impossible. Internal corrosion of the coolant passages is another problem if a corrosion-inhibiting coolant was not used.
Stag Mk2s originally came with a radiator fan cowling to increase efficiency. Many of the cowls were removed when the original engine mounts sagged, causing more overheating problems. New ones are now available. If you have a 16.5-inch metal radiator fan, you should plan on replacing both of the front engine mounts - a big job.
Timing chains are another source of concern, because they wear quickly and should be replaced every 25,000-30,000 miles. The hydraulic timing chain tensioners are actuated by the engine oil, so you must keep the idle rpm up high enough to maintain sufficient oil pressure. If you hear the timing chains rattle when you start the engine, but the noise goes away a few seconds later as the oil pressure comes up, plan on replacing the timing chains within the next 3000-5000 miles.
There was a brief period when crankshaft bearings wore out prematurely due to a temporary machining problem which resulted in the wrong surface finish on the crankshaft journals. If you have to regrind the crankshaft, make sure that it is properly hardened afterwards or you'll have a disaster in a very short time.
A leaking water pump seal will cause coolant to leak out of an opening below the water pump cover, on the flywheel side of the waterpump housing. The intake manifold gaskets are supposed to seal the fuel/air mixture flowing from the manifold into the heads, as well as coolant flowing from the heads into the manifold. These gaskets can allow coolant leaks.
Other coolant leak sources could be from the thermostat cover, bypass hose, or heater return hose.
The water pump cover gaskets are well designed and rarely, if ever, leak. Fuel leaks may be from improperly adjusted carburetor floats or leaking needle valves.
Oil leaks are probably from the camshaft cover gaskets.

Transmission

The Stag can wear out its synchromesh in second and third gears. They also tend to suffer from gearlever buzzes after a lot of use.
The automatic transmission (Borg-Warner BW35) tends to engage Reverse and Drive with a lurch if the idle speed is set too high. This problem can also be accentuated by worn driveshaft U-Joints.
Reluctance to shift at speed can be caused by a poorly adjusted downshift cable.
A metallic ping from the propellor shaft can be heard if the differential input flange bolts are loose.
If the differential pinion oil seal fails, diff oil will flow into the extension housing and wash away the grease for the quill shaft bearing. A visible oil leak from the pinion flange area means trouble.

Conclusion

The horrendous reputation for unreliability that the Stag earned when new (and as a secondhand car) are now so well documented that any problems that spring up will be a straightforward fix. Not only that, but the specialist support is so extensive, and parts supply so complete, that any owner won't be immobilised for long. The question is how much appetite you have for fixing problems.
The best thing to do is go for the best Stag you can possibly afford, with all of its problems fixed for you, and enjoy one of the finest sounding, stylish grand tourers ever made.
There are plenty of Rover V8 powered versions, some better converted than others. Although they require less maintenance (and Rovers have their own problems), they also lose a fair amount of character. The Triumph V8 has a soundtrack all of its own that no other engine gets close to matching... and unlike in the 1990s when Rover V8 powered Stags generally cost more, it's now the other way round. And rightly so.

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