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Old January 8th, 2011, 09:51   #1
Join Date: Oct 2010
Location: Brunswick, New York
Fuel Economy: Jetta TDI 98 48 miles to gallon
Default Block Heater

I don't understand some members of this TDI Forum. The some members keep referring to something called "frost plugs". What they are calling "frost plugs" is the hole or holes where the steel (cast iron, aluminum, etc.) is poured into the sand mold. If you didn't have these holes, how would the engine block get made, they are not made from a single block of material. After the engine is poured and pulled out of the sand, the hole or holes are machined out the holes are plug with metal plugs to keep the water or oil from leaking out. These holes are later used to put in a "block heater".

It seems the some members do not know what they are talking about or they are promoting the other type of heaters (inline heaters) that are not the block heater type. The membership might be right in referring that certain engines don’t have “frost plugs” but all engines have some type of plug to keep the fluids in.

I had the same problem with my 98 jetta TDI. Brand new battery, new oil, I keep the car outside, temperature around 20 degrees, took over 20 minutes of trying to get the car started. Glow plugs were working fine, just to cold to start. I had asked the forum about heaters. The membership kept referring to an “inline heater” which runs around $130 to $150 plus installation. I had asked the membership what about “block heaters” they cost around $40. Membership said, “oh your engine doesn’t have “frost plugs”. I contacted autocoolingsolutions.com asking them about my jetta. They told me that they had a “engine block heater” for my car. I told auto cooling solutions that the TDI forum said that there was not any “frost plugs” on my engine. They told me that, “well we sell thousands of these units”. So I bought one. I have a great mechanic who’s day job is working on large diesel trucks. I brought the engine block heater to him, he said, “that’s the one”. I asked him how he was going to put it into the engine, he said, where the “sand plug is located”. I asked him about the “frost plugs”, he said, never heard of “frost plugs”. He said that the TDI Forum membership must be referring to what is called the “sand plug or plugs”.

On a Jetta 98 TDI made in Mexico, the “sand plug” is located behind the engine, underneath the Turbo charger. My mechanic had to take off the charger, then make a tool to reach in, poke a hole into the “sand plug” and pop it out. “Sand plug” is a (simple metal plug), then my mechanic placed the “engine block heater” into the hole. The “engine block heater” is designed for this model of engine.

Now, when I have to start the car say if the temperature is under 32, I only have to plug the into the heater block for an hour. Jetta starts on first try.

So I’m confused with some of the TDI forum membership, saying there is no “frost plugs” on this type of car engine. Maybe someone can explain to me and the membership how I was able to place an “engine block heater” into my engine where some of the membership said I wouldn’t be able to.

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Old January 8th, 2011, 10:21   #2
Vince Waldon
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Originally Posted by bradleysjohn View Post
Maybe someone can explain to me and the membership how I was able to place an “engine block heater” into my engine
It *has* been explained to you, multiple times in multiple threads, with pictures. Here's one example:


To sum up:

- you have an early (AHU) TDI block... it *has* frost plugs and so a conventional block heater can be installed...like you did. If someone told you your engine didn't have a frost plug they must not have noticed you have a 1998 TDI.
- the later TDI blocks (1999.5+) ALH, BEW etc do not have frost plugs and so a conventional block heater cannot be installed. Coolant heaters are the order of the day for those blocks.

Here's a picture of the back side of an ALH block... again... look ma, no frost plugs:

Vince Waldon Edmonton AB Canada

Note: The above is to the best of my knowledge- but at the end of the day simply interweb opinion, worth EXACTLY what you paid for it, and if used done so at your own risk.

Last edited by Vince Waldon; January 8th, 2011 at 10:24.
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Old January 8th, 2011, 10:44   #3
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You have starting issues. All TDI should start right up with no problems in NY winters. Putting on any sort of heater is just a band-aid to the real problem. Plenty of info around here to troubleshoot hard cold starting.
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Old January 8th, 2011, 10:52   #4
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Frost plugs VS Frost Heater.....

Frost plugs as Vince indicated

Frost Heater from Terry Frost.. This unit heats the coolant and uses thermo siphoning action to heat the engine block.
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Old January 8th, 2011, 10:55   #5
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My 59 Chevy has frost plugs, never heard them called sand plugs before. Frost plugs have been around forever. What they are supposed to do is pop out when the coolant freezes inside the block, rather than cracking the block if they weren't there. Back in the old days, people used water in their engines all the time.

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Old January 8th, 2011, 11:57   #6
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Most engine blocks, including VWs are cast. The 'frost plugs' that are in the older engines and absent in the ALH and later models are intended for pressure relief in the event the engine becomes frozen. It has nothing to do with the casting or machining of the block.

Frost plugs are becoming dated. Engines have less coolant issues and thus, less problems with low anti-freeze levels and frozen and broken blocks.

But it has nothing to do with sand casting.
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Old January 9th, 2011, 06:03   #7
Join Date: Oct 2010
Location: Brunswick, New York
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I stand corrected.


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Old January 9th, 2011, 06:59   #8
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Originally Posted by Franko6 View Post
Frost plugs are becoming dated. Engines have less coolant issues and thus, less problems with low anti-freeze levels and frozen and broken blocks.
Agree with everything else except the reasons why frost plugs are not found on our engines (and others presumably).

I am not sure how a frost plug would help with a low anti-freeze level, it wouldn't be needed if the block froze as there would be a space in which the ice could expand into.

I think that the primary reason that designers of engine blocks do not put in a frost plug is simply cost. Every design feature requires extra labour and produces casting rejects. Not very many people these days open up the hood of their car and muck about with the coolant. Fewer cooling systems have owners that add water to them and fewer get frozen and therefore don't need expansion plugs.

Another reasons is that people are better educated. When I started owning and driving cars back in the 70's. It is my opinion that car owners then didn't know or liked to flirt with danger. I had a high school friend who was heavy duty mechanic who worked for a truck fleet. The fleet manager thought he could save money by running the truck on either weak or no antifreeze in the cooling systems. One morning, there was a early frost and half the trucks parked out side had cracked blocks!

About that time, when I was living in Calgary, I had a friend from Victoria, BC (never freezes there) who was draining his radiator none night. When I asked him why, he said that he didn't have antifreeze so he was draining the block so it wouldn't freeze during the night. I told him that draining the radiator is not going to help but he didn't believe me until he had that confirmed by a mechanic.

Someone whom I trust told me that a municipal buses have nothing but water in their cooling system as a cost saving measure. In the event of a winter breakdown, the drivers are instructed to drain the blocks before the freeze. Not sure if that was true, but it explained why I saw that being done one day.

From my experience, frozen engine blocks were the result of stupidity and ignorance of someone maintaining their own coolant levels in a day and age that lower manufacturing quality resulted in cars that leaked. I don't think that hardly happens to day. These days, cars almost never leak and if they do, warranties are longer and owners are more apt to have a mechanic fix and refill their coolant bottles.

However, if there is one thing that I would like VW to change (do you hear me VW). I wish they would have put in an expansion plug into their block. When a blockheater is put here, it heats more economically and efficiently. Less energy is lost because the heater is outside the block. The heated coolant moves and mixes about the block. With an in-line heater, most of the heat collects in one part of the block and the warmed coolant does not seem to get mixed very well until the engine starts up.
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Old January 10th, 2011, 09:03   #9
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freeze plugs,frost plugs. what ever you wanna call them. are not there in blocks to pop out when/if the coolent freezes. they like said above where there when they cast the blocks. and thats its.

granted you may get lucky and pop one out when/if it ever freezes. but that is not what they are intended to do. you can and will alot of the times still freeze and crack a block.
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Old January 10th, 2011, 10:00   #10
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Originally Posted by Jack Frost View Post
I am not sure how a frost plug would help with a low anti-freeze level
I'm pretty sure he meant not enough anti-freeze in the water/anti-freeze ratio. [IE - The coolant was 'full' but the ratio of anti-freeze was so low that it still froze.]
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