TECH TIPS

Courtesy of

 

Ref: TR6 Manifold Gasket Replacement

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1. One side of the commonly supplied gasket is bright and shiny (metalized) and the gasket could be installed with this in or out. However:

This gasket has a metalized surface to allow the creep (expansion) of the high temperature exhaust manifold and the relatively cold aluminium ( high expansion / contraction) intake manifold against the water cooled cylinder head. Depending on design parameters, creep (expansion) of differential temperature / expansion surfaces under clamping pressures, can result in short life of a manifold gasket that has a high friction surface, so for this reason, the shiny (metallized) side should be facing out. Clean all surfaces to remove every trace of the old gasket and Do Not use any sealants.

When doing a rebuild or repairing a manifold gasket failure , re-face the exhaust manifold and check the intake for any flange-face warpage. (warped exhaust manifolds are common and can result in a cracked casting if not addressed).

Often, one finds manifold nuts seized to studs. It is important that the nuts be removed from the stud and the studs refitted to the head. Preferably, new studs should be installed. Never put back onto the engine studs that have nuts seized to them, (or substitute a bolt), as the potential for a gasket failure could occur. Make sure only original NF thread (National Fine thread ) studs are used. When installing these studs, it is imperative that the shortest thread section of the stud goes into the head or gasket clamping pressure could be seriously compromised. Lightly oil all thread surfaces and using new nuts, torque as per factory specification making sure the clamp bridge pieces are correctly positioned.. Re-torque after approximately 500 miles.

Happy Motoring

Britcar Tech Tips # 19

Email Britcar@rogers.com

(905) 576-6444

 

 

Subject:    Late MGB Expansion Tank Coolant Level

 

 

How the expansion tank works.

The cooling system on late models employs an expansion tank that allows coolant from the engine and radiator to expand into the tank when the engine is at its operating temperature.  Conversely, coolant flows back into the engine when it cools down.  With this system design to function, the entire cooling system must be free of any coolant or air leaks to avoid coolant depletion. 

 

Due to the design of the MGB expansion tank, fitted to later models (R/H inner fender),  it is extremely important to maintain a minimum coolant level in the tank no less than half full.  For an adequate coolant level to be maintained within the engine and radiator,  expansion tank level must not allow the coolant siphon pipe that goes down to the  bottom of the tank to be exposed.  Seeing coolant in the lower tank portion does not necessarily mean there is coolant in the engine.  Failure to ensure an adequate amount of coolant in the expansion tank can result in engine coolant starvation and subsequent overheating and severe engine damage.

 

The typical overheating scenario is for a small leak to deplete the expansion tank and then air will be sucked into the system with each cooling/heating cycle. Eventually a high engine coolant temperature is observed due to a large quantity of air present in the radiator and upper engine coolant galleries. 

 

Important Note: A major loss of fluid in the engine and radiator cannot be replenished by filling the expansion tank as there is no gravity connection between the tank and the radiator, only a siphon hose.  The system fill plug fitted in the top of the thermostat engine must be removed and coolant added through the aperture until the system is full. Run the engine for a few minutes then remove the expansion tank cap to depressurize, then remove the fill plug again and verify the system is full. Always pressure test for leaks following any work that involves the cooling draining.

Britcar Tech Tips #20

Email:    Britcar@rogers.com

(905) 576-6444

 

 

Subject:  TR6 Coolant System Level

 

 

How it works. 

The coolant for the engine is initially added via the radiator cap and a plastic expansion bottle located in the L/H inner front fender-well takes expanded coolant as the engine warms up and returns it as the engine cools.   This system design requires that there be no coolant or air looks including the hose to the expansion bottle, the bottle kept at least half full, the correct radiator cap fitted and in good operating condition. .

 

Problems

Due to the fitting of a low profile radiator in order to have a low hood line, the TR6 coolant level in the engine is marginal with the exhaust ports in the cylinder head gallery being barely covered so even minor water loss can induce overheating at low RPM or when stopping after an extended period of hard driving.  When the system is in good order it will be adequate.  It is very important that the pressure cap be correct and in good operating condition, the hose to the expansion bottle be leak free and extending down to the bottom of the bottle, and there be no coolant or air leaks.

 

A consistent problem with this Triumph model is that the radiator fill level is lower than the thermostat outlet.  Loosening of the top hose seal from build up of corrosion of the aluminum thermostat outlet neck and compression of the hose material by the clamp (very much so with the original style clamp) is the most common system fault. Often, no coolant leak will observed in this area but air is allowed to enter via the poor hose seal when the system is under a slight vacuum (cooling down).  This air entry while the system is under a slight vacuum prevents the system from siphoning back the earlier displaced fluid. Coolant depletion and overheating can be experienced especially if there is another coolant leak in the system.

 

A good practice is to ensure that the radiator expansion bottle is frequently monitored for the correct fluid level with an occasional check of the radiator level by removing the cap when the engine is cold, (level must be at the radiator fill neck so that there is no air space in the radiator). Tightening top hose clamps, along with a system pressure check periodically, is recommended.