Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Inline radiator heater

Inline radiator heater

Inline radiator heater

I want to install the inline radiator hose heater. This heater heats the water in the radiator and up to the thermostat. But the thermostat will be closed, so how can it warm the engine block? The genset engine I have is very small, 1 ci^3 displacement. It has hard time to start in winter. Inline radiator heater looks good option, but I have hard time to understand if warm coolant is not going inside how it will warm the engine?
I have attached image for reference.

RE: Inline radiator heater

You will also need a pump unless you can get creative with plumbing and use convection.

The red and yellow lines form a loop through the water jacket when the thermostat is shut (cold).

RE: Inline radiator heater

Hello @TugboatEng, thank you very much for responding.
I am not following flow in the loop when the thermostat is cold.
What I understand is that inlet side of engine coolant has thermostat and when it is shut until certain temperature is reached inside the engine block. As soon as certain temp is reached, it will open up to let fresh coolant inside and let flush out warm coolant towards radiator.
Not sure how creative plumbing can help with that?

RE: Inline radiator heater

Engine thermostats do not seal bubble tight. They have vent holes to allow air to pass and enough liquid flow to allow warm fluid to reach the sensing bulb of the thermostat. All the engine heaters that I have seen use thermo-siphon flow with the heater mounted low on the engine. A heater can also be placed under the oil pan and work. Applying heat is not the only consideration. You also have to consider heat losses. The temperature of the engine when not running is determined by when the heat losses equal the heat input.

RE: Inline radiator heater

ro_kru, it varies from engine to engine but most systems I come across operate the engine jacket water as a closed loop with the full water flow passing from the jacket through the thermostat and to the water pump making a closed loop. As the system reaches the setpoint, the thermostat opens blocking B and creating a venturi to pull from C.

RE: Inline radiator heater

There are a variety of solutions available on the market, depending on what the problem is that you want to solve and how much you can afford.

Generally with diesel engines, the problem is poor staring from cold.

With a small engine, the basic solution is a thermosiphon preheater, usually powered by electricity. This just connects to the engine or is fitted to the lower engine coolant inlet. The heated coolant rises displacing the cold coolant. Without a thermostat, the engine temperature will rise until equilibrium is reached. Sensible users have a heater with thermostat.

For larger applications you can fit a separate preheater unit with a pump. You can also have separate heaters in the lube oil system, and even the start battery.

Preheat Engineering are one of the market leaders in UK. There are many others worldwide. If you get in touch with their local distributor, you will probably find that they have a pre-engineered solution for your engine and application. No need to re-invent the wheel!

We approached them for a heater for a diesel engine shunting locomotive manufactured in 1946. They knew the engine, and application and had an off the shelf solution.

RE: Inline radiator heater

Thanks for responding.
The problem we are facing is that its hard to find frost plug adapter for 30mm.
The engine manufacturer suggest to use screwed opening to circulate heater water inside block. But that opening is close to radiator thermostat. so, before heated coolant start circulating through engine block, it opens radiator thermostat, heated coolant flows to radiator rather than circulating inside block.
We used following heater.
We are planning to go for lower watts but again we have doubts.


RE: Inline radiator heater

The other question I have is that if radiator thermostat is configured to open between 180F to 195 F, and block heater is ranged between 100 to 120 F, why radiator thermostat is opening up so early. I am trying to understand how its working. Is it due to heat capacity of the radiator thermostat is low?
Please, explain.

RE: Inline radiator heater

It sounds as though you are supplying heated water to the top of the engine near the thermostat. You must apply heat near the bottom of the engine and return water to the heater from the top of the engine.

RE: Inline radiator heater

The thermostatic valves don't open, they bypass. Under cold conditions the water bypasses the radiator. Under hot conditions the bypass closes and water passes through the radiator. There is always flow through the thermostat, it is never shut. The "thermostat" that you see moving is moving to shut the bypass, not opening.

RE: Inline radiator heater

It would sure help if we knew exactly which engine the original poster was dealing with, and perhaps even a schematic diagram of the cooling system, because there are a few different ways that they can operate.

Normal automotive cooling systems have two different directions for the fluid to flow after exiting the engine (normally in the cylinder head). One flow path is "always open" and leads to the interior heater (no thermostat) and then back to the coolant pump. The other flow path is "normally closed" (by the closed thermostat) and the thermostat opens when a certain temperature is reached, which allows flow to the radiator and back to the coolant pump. The thermostat can either be on the hot side of the engine (letting flow go through the radiator if the engine-out temperature is beyond a certain point) or it can be on the suction side of the coolant pump (effectively regulating the inlet temperature of the coolant pump - it always draws through the heater-core loop, and if the temperature is above a certain setting then it also draws through the radiator). In either case ... the interior-heater circuit is always open.

With that system then a strategically placed coolant heater can warm up the whole engine, because the flow can go through the engine then follow the coolant path through the interior heater because that flow path is always open, even if the thermostat is closed.

But, I am going to ASSume, that this particular engine's cooling system does not have an interior heater.

It still may have a flow path that is always open, bypassing the thermostat and radiator. Look for auxiliary oil-cooler circuits or something of that sort.

Even if that's not the case ... the thermostat generally has an always-open small hole to allow a small amount of coolant to flow through it, even when the engine is cold. If there is zero flow through it then unless there is a bypass path that draws flow across the sensing side of the thermostat (e.g. interior heating) it won't react quickly enough to start opening as the engine warms up. That small hole may be enough to do what is needed here.

RE: Inline radiator heater

I am attaching few images for your reference.
The engine itself is 1000cc PG engine.
The core plug adapter is hard to finds, so, we are trying to find a way for warm coolant to make its way inside engine.
We tried hotstart 1000 watt block heater but it will open the thermostat and fluid will bypass to radiator.

RE: Inline radiator heater

I see spark plug caps and what looks like a lambda (oxygen) sensor. Is this a petrol engine or a natural-gas engine? The lambda sensor suggests modern emission controls. Fuel injection?

What ambient temperature are you trying to start it in, in which it encounters difficulty?

The petrol engines in my own vehicles have no trouble starting in -20 C, below that the battery had better be good, -30 C is an operational minimum.

What is the "failure mode" that prompts the no-start?
- Cranking too slowly
- Voltage to ignition and fuel injection systems drops too low for the spark plugs to fire and the fuel injectors to operate
- Cranks but doesn't fire (fuel injection calibration not correct? wrong air/fuel ratio for cold starting?)

Crank-too-slow and voltage-too-low are related problems caused by the combination of the engine being harder to crank and the battery not having enough jam to get it done.
- Is the battery big enough?
- Is the battery in good enough condition to get the job done?
- Battery and starting-motor and ground-strap terminals secure and not causing abnormally high resistance?
- Engine oil viscosity too high? What's the engine manufacturer recommend for oil viscosity in cold weather?

Synthetic oil of viscosity 0wXX (XX is whatever viscosity the engine manufacturer recommends) is the way to go. Good quality 0w20, 0w30, 0w40 synthetic motor oils are all readily available. Use them.

RE: Inline radiator heater

Hello Brain,
The problem is engine won't fire up in cold weather.

RE: Inline radiator heater

Right. So. What happens when you turn the key / press the switch?

Does it:
A: Do absolutely nothing. No sign of any life whatsoever. No clicks from relays, no attempt from the starting motor to rotate the engine.
B: Go "click" from a starting motor relay, but otherwise, no sign of any life whatsoever, no attempt from the starting motor to rotate the engine.
Sub-question: What's the voltage across the supply to the ignition when this happens? Full battery voltage, or reduced? Give me a number for full battery voltage (no attempt being made to start it), and what's the voltage when attempting to press the "start" button?
C. Click from relay and starting motor rotates, but very slowly, well below normal cranking speed.
Sub-question: gimme the voltage across the supply to the ignition circuit when cranking the engine. Same reason as above, "is there enough voltage to operate the ignition and fuel injection systems".
D. Engine cranks with the starter motor at reasonably close to normal operating speed, but there is no sign of attempting to fire.
Sub-question 1: Got spark while cranking?
Sub-question 2: Got fuel being delivered while cranking?
Sub-question 3: How much compression does the engine have? Cranking with throttle held open and all spark plugs removed, gauge measuring compression in one cylinder - check all of them - give me all of the numbers.

What sort of fuel delivery does this engine have? (You haven't even answered whether it is natural gas or propane or LPG or petrol!)

More information ... better answers!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close