How to Perform a Water Hose Bypass on your Non-Turbo (VG30DE) 300zx

There are a heap of articles out that deal with water hose routing on the Twin Turbo VG30DETT motors but often see people asking about how to route the hoses for a Non Turbo VG30DE motor. This article will show I do it.

Why I go to the trouble of bypassing rather than capping the outlets... rubber blanking caps typically do not have the same composition and chemical linings found on proper heater hose and can fail prematurely.


For the job showed below I used 1m of Gates Safety Stripe in 5/16" ID and 4x Norma Torro Hose Clamps in 12-18mm. The specs on the Gates heater hose exceed the requirements of the operating conditions, and the hose clamps have all the features (solid band, stainless steel construction, rolled edges, hex drive) that I like.

A note on heater hose... Generally speaking I would prefer to retain the OEM constant tension clamps however in this case it was not possible due to the wall thickness of the Gates heater hose being 50% thicker (which in itself is a good thing) than that of the OEM hose as shown below. So as in life it is in auto repairs and I have compromised. I have found on previous jobs that Dayco heater hose will fit under the OEM spring clamps if it is available andthat is your prefernce.

The OEM heater hose has a 2.75mm wall thickness.
The Gates heater hose has a 4.2mm wall thickness.


I have started this guide with the intake manifold removed and the OEM cooling circuit stripped down to the Right Hand Side (RHS) and Left Hand Side (LHS) heater pipe assemblies. There are already many articles such as This One that detail a procedure Intake Manifold removal.

The RHS heater pipe assembly has two barbs, an upper one pointing to the LHS of the vehicle and a lower one pointing up. The LHS heater pipe assembly has a barb pointing to the RHS of the vehicle and another on the rear LHS of the vehicle near the PCV outlet fittings. These are shown below.

RHS and LHS heater pipe assemblies.
LHS heater pipe assembly lower barb fitting

To retain factory coolant flow we are going to connect the lower barb on the RHS heater pipe assembly to the upper barb of the LHS heater pipe assembly. I prefer to keep the screws for the hose clamps facing the firewall to reduce the chance of interference when refitting the Intake Manifold.

Fitting the first bypass hose.

The upper barb on the RHS heater pipe assembly is then connected to the lower barb on the LHS heater pipe assembly as shown below.

The second bypass hose installed.
Second bypass hose installed.

And that's it! If you have the resources I suggest pressure testing the cooling system before refitting the Intake Manifold.

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