I have been searching the internet for information on my 5432 Universal diesel and found that like with the old downeaster websites that a lot of the info I found a year or so ago is going away. So I am going to compile what I can find here to make sure all of it doesn’t disapear. I will put anything here to do with the universal engines that I can find as well as crossover parts that you can get from a kubota dealer.
First site I found that still had some info was a copy of a email list conversation.
Here is the latest info I have found after getting my numbers from the motor
and searching some more. Ultimately,I think we can get very close to the
right parts for the block and most systems from this info,however,the
marinized parts for the exhaust,cooling,intake and the trans will always
deviate to some degree.
The Model 5432,a 91 cu in,32 hp,4 cylinder,based on the Kubota V-1501
block,was built from 1978 to 1982. It was also called the Atomic diesel.
Approximately 650 were sold. It was replaced by the Model M40,which was
produced from 1982 to 1998. The Model M-40 was also a 4 cylinder model,and
the same size at 91 cu in and 32 hp but it was based on the Kubota V-1502
block. Approximately 360 were sold. So it looks like the 5432 was spread
over two block designations (and they are different).
My engine is a Universal 5432 (Atomic Diesel) Universal Ser# 316207 and is
very similar to Westerbeke’s M40,the Block is stamped Kubota model# 1502
and Kubota Ser# 17964. My boat was built in 1987.
The model designations Below:(see the resource website above for more on
each model,as there are variations within each designation!,for more on
tractors that use your motor see:http://www.tractorsmart.com/enter.htm)
Universal / block numbers / Years produced / Kubota Tractor used in
5432 V-1501 1978-1982 L285 &L345
M40/5432 V-1502 1982-1998 L285 &L345
Kubota Corporation of Japan has a very good reputation for building
reliable,clean-running small industrial diesel engines…and yes,Beta
marine engines are marinized Kubota engines. Most small marine engines are
marinized versions of Kubota engines and are the basis of Beta marine
engines (England),Westward marine engines (Canada),Nanni marine engines
(France),Phaser marine engines (USA –Florida),and the oldest and best
known:Universal marine engines (USA –Massachusetts –subsidiary of
Westerbeke Corporation). [All Universal diesel engines are Kubotas.] As
well,Kubota industrial engine dealers in many countries can supply a
custom-built marinized Kubota diesel on request.
BTW some warnings about oil filter sizing,antifreeze gelling &alignment:
MODEL:Kubota,Universal &Westerbeke Propulsion Engines
SUBJECT:Oil Filter Hazard –20 mm filter on 3/4″adapater
Over the years Universal diesel marine engines have been fitted with oil
filter adapters (the threaded stud that holds the filter onto the engine)
with both metric and imperial threads. That is why a different filter is
specified for some models that seem very similar to others.
The Universal M12,M2-12,M18,M3-20,M3-20A,M-25,5421,M25-XP,M25-XPB,
M4-30,M-35,M-35B,M-40B use a metric thread filter (#300209),while the
Universal M15,5411,M-20,5416,M-30,and 5424 use an imperial thread
filter (#299381) [The Universal 5432 and the M-40 with a Kubota 1501 block
use a large imperial thread filter (#299584),while the M-40 with a Kubota
1502 block and the M-50 use another large imperial thread filter (#299927)].
MODEL:Westerbeke,Universal,Vetus Diesel Marine Engines
SUBJECT:Diesel Marine Engine Antifreeze “Gel”Formation
Many automotive antifreeze products contain high amounts of silicate
designed to protect aluminum engine parts and aluminum radiators from
corrosion. When antifreeze is not mixed with fresh water in the correct
mixture (1:1),or changed regularly(usually about every 3 years) it can
cause the silicates to drop out rapidly and create a gel condition which can
block the water jackets and heat exchanger…causing severe overheating.
The prevention of antifreeze gel formation is to use the correct,
brand-name,regular life (green) antifreeze in the correct mixture with
clean,fresh water,and change it regularly according to the engine
maintenance manual specifications.
Removing the gel formation from engine water jackets is difficult. Heat
exchangers and engine water jackets must be flushed with a caustic solution,
How do I align my engine?
Universal inboard marine engines should be installed so that the engine
mounts are securely attached using the correct fasteners,aligned with the
propeller shaft to a tolerance of .05 mm (.002 in) per inch of shaft flange
diameter,measured at the engine and propeller shaft flange face,with the
propeller shaft aligned and centered with the propeller shaft strut cutlass
bearing and stern tube. During adjustment any flexible (ie rubber) engine
mounts should be extended using pry bars or wedges to bring the engine into
the same position it will be when the boat is under power at normal cruising
speed. To determine engine mount deflection position under power,measure
the position of the engine close to each mount with the engine stopped,and
then measure it again under power (you can do this tied to the dock) using a
dial gauge or fixed pointer. Excessive deflection of the engine under power
may mean the engine mounts are loose or the flexible engine mount material
is worn out.
When aligning the engine,adjust the alignment with the 2 rear engine mounts
and 1 forward mount (for V drive engines adjust 1 rear engine mount and 2
forward mounts),leaving the 4th mount loose until the alignment is correct.
Take up the clearance on the 4th mount with the lower adjusting nut or
shims. Then tighten all 4 mount top nuts. This will prevent the engine
block/pan from being twisted (and possibly cracked) during final tightening
of the mount nuts. If the alignment changes when the top nuts are tightened,
the 4th mount clearance was adjusted either too much or not enough. Engine
mount deflection and engine alignment should be checked once per year,as
well as whenever the boat has been lifted from the water,and mounts
replaced or tightened and alignment adjusted as required. Always use
“shakeproof”lock washers on engine mount nuts
Anyway,a lot of info. Validation is always paramount before ordering any
parts. It is good to know we have alternatives!
Steve and Paul.
Nice work on the research. It looks to be a little more complicated than I
was thinking,though I was figuring on just using the manual for things like
injectors,etc. I have found that the list I provided the link to on the
Newport Web page is pretty good for oil filters,belts,etc. for the 5416
engine that I have. The tractor smart manual that is listed for the L185
also had the same number for the injectors that John Ryan had listed in his
email. In any case,I have found it best to attempt to validate the Tractor
Manual with one other source prior to purchasing the part.
I wonder if there is a way for us to get our whole newport list working on a
combined list of aftermarket parts for these Universal Diesel Engines? I
have a list of Universal parts and part numbers from my Universal Parts book
in my sailboat tracker database in my palm and as I find alternate sources,
I add the alternate part number and manufacturer/vendor as well.
Thanks for your input. I hope I didn’t give too many false hope for finding
an authoritative listing of Kubota parts for our Universal Marine Engines.
I appologize for making it look overly simplified.
Steven Home Mail wrote:
“It isn’t that simple”…well put Ronnie. Any suggestion of a one to one
match for all parts would be folly. Maybe at least a confirmation of the
Kubota engine model number would be a improvement. A list of those part
numbers that are confirmed to really match as well as a list of aftermarket
parts confirmed to work (oil filters,belts,etc) would be a laudable long
The L2850 is a different tractor with a different motor and transmission.
I found the match to the L285 tractor with the engine model V1501A by
comparing specs for bore,stroke,displacement and HP. They all lined up
perfectly for the L285 with the V1501A motor,but it is still a speculative
match with no confirmation. It also matches up with the V1501-DA engine (in
fact all specs except the piston ring gap AL are exact matches),but these
are different motors…so,we will not be sure until a call to confirm. The
key is the motor serial number for good parts matching (even within the same
motor model). There are many parts (mostly external…cooling,exhaust,
intake and fuel pump) that are different for each tractor and especially the
marine application,I doubt that many of these particular parts would work
for the 5432 in any case. Bottom line,call and ask with your serial number
(found at:http://www.engine.kubota.ne.jp/english/parts/index.html). Once
you have the number you can then shop around (obviously).
A brief review of the parts manual showed that many of the parts external
parts were indeed different,but the rest looked like the beast we call the
The L285 is listed on the parts manual page at:
http://www.tractorsmart.com/PartsBooksKubota/Lseries_Manual.htm. They will
request that you give them your email and they will forward the document
link to you. I did it and the link for the doc came right away,the file is
a 1.2 mb PDF file (for adobe acrobat reader). They don’t have a quick parts
finder section for the L285 like they do for the L285 and others. If you
desire I can forward the doc directly…let me know.
And there is not a L285 listed…I do see an L2850 however.
On Apr 8,2005,at 11:19 AM,Paul McQuillan wrote:
Maybe I didn’t give him enough info,but I got back a waffle and different
tractor model. That’s iinstead of the direct answer that Steven received….
Tractor Smart website says the Universal 5432 = the Kubota Engine model
V1501A found in tractor model L285
The smaller engines seem to be clearly defined already. Maybe we can clear
this up on the 5234 so that John Q can post on website.
It isn’t that simple.
The Kubota L345 tractor had a V1501-DA engine.
Kubota engines used in the Kubota tractors are different than the ones used
in other applications.
Different water pump,heads,timing covers,injectors,starters,etc.
There is a source for Kubota engine parts for applications outside the
Kubota tractor engines.
That site has a dealer locator and these guys are equipped with knowledge on
the other applications.
See the attached picture on Kubota engine serial number locations.
—–Original Message —–
Sent:Thursday,April 07,2005 9:25 PM
Subject:Kubota parts for V-1501 block
If I know the block type,V-1501,which tractor model has the matching
>Steven Home Mail wrote:
>>The Tractor Smart website says the Universal 5432 = the Kubota Engine
>>model V1501A found in tractor model L285
>I’ve looked at the site,and can’t figure out how you arrived at this
>conclusion. Could you describe the process so I could do the same for my
here is a very comprehensive post on the engines history that I found
though there was some discussion of its accuracy. So for what it is worth here it is..
Universal Engine History
In my continuing search for Universal to Kubota crossover charts,a few gems appear now and then. Note to Moderator;please archive this for future reference
This has been published on the Catalina 30 website but this version is from Hess Marine? and it varies slightly from the version on the Catalina 30 website.
Take it for what it’s worth but when trying to track down parts for say a Universal 5432,it helps to know that you likely have a V1501 or V1502 Kubota block depending on the year of manufacture.
History of the Universal Diesel Motor
In the early 1970’s sailboat manufacturers began fitting Yanmar diesel auxiliaries instead of the Atomic Four gasoline auxiliary,however Atomic Four sales continued to grow until their peak year of 1975. In 1976,as sales of the Atomic Four started to drop,Universal met the challenge from Yanmar by buying Kubota diesel engines and selling marinized versions,under the name Universal. Atomic Four sales gradually declined as manufacturers increasingly used diesel engines,and manufacturing ceased in 1980,with sales continuing until all units were sold in 1984. The last OEM (original equipment manufacturer) to fit the Atomic Four was Catalina,who used it up until the 1985 Catalina model year. After 1985 Universal sold only diesel marine engines,which were fitted by several OEM,including Catalina.
In 1976 the first Universal diesel was introduced. Designated the Model 5416,it was a 45 cu in,16 hp,2 cylinder,fresh-water-cooled engine producing 16 hp @ ? rpm (intermittent),based on the Kubota Z-751 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1976 to 1982. Approximately 1,000 were sold.
In 1977 the Model 5411 was introduced. It was a 31 cu in,2 cylinder raw water cooled diesel producing 11 hp @ ? rpm,based on the Kubota Z-500 block,and fitted with a Hurth HBW-50 marine transmission. It was built from 1977 to 1982. Approximately 2,900 were sold.
In 1977 the Model 5424 was introduced. It was a 68 cu in,24 hp,3 cylinder,based on the Kubota D-1101 block,and fitted with a Hurth HBW-50 marine transmission. It was built from 1977 to 1983. Approximately 1,050 were sold.
In 1978 the Model 5432 was introduced. It was a 91 cu in,32 hp,4 cylinder,based on the Kubota V-1501 block and fitted with a Hurth HBW-100 marine transmission. It was built from 1978 to 1982. It was also called the “Atomic Diesel”. Approximately 650 were sold.
In 1980 the Model 5444 was introduced. It was a 115 cu in,44 hp,4 cylinder,based on the Kubota V-1902 block and fitted with a Hurth HBW-100 marine transmission. It was built from 1980 to 1982. Approximately 280 were sold.
In 1981 the Model 5421 was introduced. It was a 52 cu in,21 hp,3 cylinder,based on the Kubota D-850 block and fitted with a Hurth HBW-50 marine transmission,built from 1978 to 1981. Approximately 1,000 were sold.
In 1981 the Model 5421 was replaced by the Model M25,a 52 cu in,21 hp,3 cylinder,based on the Kubota D-850 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1981 to 1986. Approximately 3,650 were sold.
In 1982 the Model 5432 was replaced by the Model M40,a 91 cu in,32 hp,4 cylinder,based on the Kubota V-1502 block and fitted with a Hurth HBW-100 marine transmission. It was produced from 1982 to 1998. Approximately 360 were sold.
In 1982 the Model 5411 was replaced by the Model M15,a 45 cu in,16 hp,2 cylinder,fresh-water-cooled,based on the Kubota Z-500 block and fitted with a Hurth HBW-50 marine transmission. It was produced in 1982 and 1983. Approximately 370 were sold.
In 1982 the Model 5416 was replaced by the Model M20,a 45 cu in,16 hp,2 cylinder,fresh-water-cooled,based on the Kubota Z-751 block and fitted with a Hurth HBW-50 marine transmission. It was built in 1982 and 1983. Approximately 230 were sold.
In 1982 the Model 5444 was replaced by the Model M50,a 115 cu in,44 hp,4 cylinder,based on the Kubota V-1902 block and fitted with a Hurth HBW-100 marine transmission. It was built from 1982 to 1997. Approximately 520 were sold.
In 1983 the Model M-12 was introduced. It was a 24.4 cu in,10 hp,2 cylinder based on the Kubota Z-400 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1983 to 1988. Approximately 1,200 were sold.
In 1983 the Model M-18 was introduced. It was a 34.8 cu in,14 hp @ 3,200 rpm,2 cylinder,based on the Kubota Z-600 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1983 to 1988. Approximately 2,400 were sold.
In 1983 the Model 5424 was replaced by the Model M-30,a 68 cu in,24 hp,3 cylinder,originally based on the Kubota D-1101 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1983 to 1987. The Model M-30 was the same size as the Model 5424,but later M-30 engines were based on the Kubota D-1102 block. It was built from 1983 to 1987. Approximately 400 were sold.
In 1986 the M-25 was replaced by the Model M-25XP,a 57 cu in,23 hp,3 cylinder,based on the Kubota D-950 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1986 to 1999. Approximately 3,100 were sold.
In 1987 the Model M2-12 was introduced. It was a 26 cu in,11 hp,2 cylinder,based on the Kubota Z-430 block and fitted with a Hurth HBW-50 marine transmission. It was built from 1987 to 1997. Approximately 320 were sold.
In 1987 the Model M-35 was introduced. It was a 75.5 cu in,30 hp,4 cylinder,based on the Kubota V-1200 block and fitted with a Hurth HBW-100 marine transmission. It was built from 1987 to 1997. Approximately 280 were sold.
In 1988 the Model M3-20 was introduced. It was a 38.9 cu in,18 hp,3 cylinder,based on the Kubota D-640 block. It was built from 1988 to 1997. Approximately 525 were sold.
In 1988 the Model M4-30 was introduced. It was also called the Atomic Four diesel,and was a 52 cu in,25 hp,4 cylinder,based on the Kubota Y-850 block. It was built from 1988 to 1997. Approximately 470 were sold. The Model M4-30 was offered as a diesel replacement for the original Atomic Four gasoline engine. It was similar to its namesake,since it was a 4 cylinder model weighing slightly less (122 kg / 270 lb as opposed to the original’s 150 kg / 330 lb with Paragon reduction drive) and generating slightly less power (18.6 kW / 25 hp at 3,600 rpm as opposed to the original’s 22 kW / 30 hp at 3,500 rpm) with a smaller displacement (850 cc / 52 cu in as opposed to the original’s 1,065 cc / 65 cu in).
I found some pdfs online. The first is a brochure for the Universal 5432 and shows the mounting dimensions and some nice pictures of the engine with general sales blurb stuff.
The next one is a listing of different model engines
Here is a link to another history of the universal diesel engine
Here is a link to torreson’s website to purchase the zincs for the heat exchanger.
last I look the were around 8 dollars each.
After some prompting by members of this email list,I decided to complete a long-overdue valve adjustment on our Universal diesel. Along the way,I picked up a few bits of engine lore,reported below for the benefit of other weekend tinkerers.
We have a Universal M25XP. The Universal Engine manual is intended for trained mechanics and assumes that the reader knows more than I do. The missing bits stopped me in my tracks.
Here are my discoveries:
Cylinders are numbered from front to back with cylinder 1 being the one closest to the v-belt end of the engine.
When facing the front (v-belt end) of the engine,rotation of the crankshaft is clockwise.
Adjusting the valves involves a lot of rotating the engine by hand. Turning the engine operates the seawater pump. To avoid water-logging the muffler,I turned off the seawater valve.
I was initially concerned that the engine would be difficult to turn,but found that I could rotate it by hand by twisting the water-pump pulleys. It is probably impossible to start a diesel by hand but to be on the safe side I pulled out the engine stop. This also cuts off the fuel supply,preventing the injectors from flooding the cylinders.
The timing port which provides a view of the marks on the flywheel is located just aft of the rear engine mount on the left side (Left when viewed from the front (v-belt) end of the engine). For peering into the timing hole I used a mechanic’s mirror with an adjustable handle which I was able to prop in position and a penlight clamped in my teeth. A headlamp or one of those mechanic’s lights with a goose-neck and magnetic base would have been helpful.
The marks are not as described in the manual. According to the manual,there is fuel timing mark for each cylinder (labeled F1,F2 etc.) followed 25 degrees later by a top dead center mark (labeled TC1,TC2,TC3). The marks in my engine were completely different:first an unlabeled 25 degree mark,then a labeled 20 degree mark,unlabeled 15 deg.,labeled 10,and labeled top dead center. The labels were in microscopic script,reversed by my mirror (which threw me for a few minutes). The top dead center label looks like “1C”. I assume this is a badly printed “TC”. The cylinders are not numbered on the flywheel,it was necessary to identify them by watching the operation of the valves.
Before removing the valve cover,I bought a new valve cover gasket. The guy in the shop suggested coating the groove in the cover with Vaseline to hold the gasket in place long enough to drop the cover over the engine. This worked. The old gasket was held in place on the cover by a thin coat of flexible Permatex which cleaned off without difficulty,this is an alternative.
Several times during the operation I missed the marks and had to rotate the engine while watching the rocker arms until I found the compression stroke of the cylinder that I was working on. Intake and exhaust valves can be identified by observing their proximity to the manifolds.
The engine fired up immediately. Still sounds like someone is shaking a box full of loose diesel parts but the ticking of the valve-train is quieter.
Hope someone out there finds this useful.
|Description||Part #||Description||Part #|
|Air Filter||301139||Oil Pressure Switch||301206|
|Air Filter Element||301049||Panel,Standard||300680|
|Belt||239648||Pump,Fresh Water||Note (G)|
|Dipstick||299968||Pump,Mounting Gasket||Note (G)|
|Exhaust Manifold||299886||Pump,Rebuild Kit||N/A|
|Exhaust Manifold Gasket||302532||Pump,Sea Water (H)||302648|
|Filter,Lube Oil||Note (A)||Pump Mounting Gasket (H)||302678|
|Filter,Fuel Oil||298854||Pump,Impeller (H)||302875|
|Filter,Electric Lift||300128||Pump,Repair Kit||N/A|
|Gasket,Oil Pan||Note (B)||Pump Conversion Kit|
|Gasket Set,Upper||256763||(includes pump)||302837|
|Gasket Set,Complete||256738||Pump Conversion Kit|
|Glow Plug||300052||(excludes pump)||302838|
|Harness,5 FT. EXT.||300708||PTO Pulley Kit (I)||302201|
|Harness,10 FT. EXT.||300675||Pump,Fuel Lift||301385|
|Heat Exchanger||Note (C)||Spare Parts Kit A||256914|
|Heat Exchanger End Cap||299838||Spare Parts Kits B||256749|
|Heat Exchanger Gasket||299838||Starter||299574|
|Injection Hardware Kit||N/A||Tachometer with Hour Meter||300687|
|Injector Nozzle||N/A||Tank,Coolant Recovery||300238|
|Injector Return Line||Note (D)||Thermostat Element||299798|
|Isolators||300583||Thermostat Element Gasket||N/A|
|Ignition Switch||300671||Thermostat MTG Gasket||298843|
|Manuals,Operators||200157||Valve Cover Gasket||300001|
|Manuals,Parts||Note (E)||Water Temp Meter||300670|
|Manuals,Technical||Note (F)||Water Temp Sender||299066|
|Oil Drain Washer Kit||301431||Water Injected Elbow||N/A|
|Oil Pump||299961||Zinc||Note (J)|
|(A) P/N 299584 oil filter used on model 5432 (Block series 1501) side mtd.|
|P/N 299927 oil filter used on M-40 (Block series 1502) straight out|
|(B) P/N 302652 is the sump gasket. P/N 299560 is sump cover gasket.|
|(C) P/N 299835 (3 X 13) used on model 5432. P/N 299049 used on M-40 (2X16)|
|(D) Injector return line consists of (1) 299831,(1) 302547 &(3) 298784.|
|(E) P/N 200146 parts list for M-40. P/N 200147 parts list for model 5432.|
|(F) P/N 200154 service manual for M-40 &200153 service manual for 5432.|
|(G) Model 5432 uses P/N 300647 fresh water pump &300718 gasket.|
|(H) New style Sherwood pump –no end cover plate|
|Old style Sherwood Pump has six (6) end cover screws|
|Oberdorfer Pump has four (4) end cover screws|
|(I) Pulley only|
|(J) Use 301069 Zinc With 2″Heat Exchanger,301068 With 3″Heat Exchanger.|
The engine manual says the optimum temperature is 170-185 and yet Universal only provides a 160 thermostat. Go figure. Without giving a dissertation on the things that influence engine temperature,suffice to say here that Aeolus ran a steady 160 no matter how hard she was run,and that this was controlled entirely by the 160 thermostat setting in my case. She has an extremely efficient cooling system.
After a lengthy search involving all the usual steps,I found my answer. Car Quest makes a 180 and 195 degree thermostat that is an exact match. They are actually made by Stant and just rebranded by Car Quest. I put the 195 degree in Aeolus tonight and ran her up to temperature and she parked herself on 190!!! Perfect.
Car Quest part number 31979
I could just see the carbon burning off the piston rings and the valves. In my case this is especially important because I run a high % biodiesel for all the mechanical and environmental benefits,and it has a slightly higher flash point which is helped by the higher operating temperature.
As only someone who really knows their boat can appreciate,I noticed a distinctly quieter and smoother sound to her tonight while running at the higher 190 temperature.
For pictures and more of the story see my boat blog at Stories of Aeolus- Our Gulf 32 Pilothouse
I hope this helps anyone else out there who has an efficient cooling system and who worries about carbon build up with an engine that is running too cool.
I suspect that with the 180 degree thermostat that she would run between 175 and 180,which is at the lower limit of fine,but after her being run 700+ hours too low in temperature,I am anxious to run her at the upper margin of things.
The CarQuest part # for the 180 thermostat is:31978
Hope this helps.
Be sure the thermostat is for ‘raw’water cooling,one that fully CLOSES at 135 degrees (the Atomic 4 is a BYPASS thermostat system …thus works ‘backwards’than the normal automotive T-’stat’…. Im not sure the configuration of the Universal Diesel). A ‘normal’T-stat will be for 180 degrees F. and at that temperature the cooling water will more rapidly foul the engine with scale. Anytime saltwater or ‘raw’water goes above ~145 degrees F. the carbonates in the water will start to ‘precipitate’and form scale inside the engine.
For raw water cooling A4 or any raw water cooled diesel,its best to ‘descale’the engine AND the exhaust manifold with a commercial boiler descaler to remove the built-up carbonates internal to the engine and the exhaust manifold. Do this at the first sign of overheating or at least every 2 years. Suitable descaling compounds are “RydLyme”or “Marsolve”. Such compounds are ‘inhibited’and wont dissolve the engine’s base metal;plus,they can be ‘dumped overboard’as they rapidly decompose/dilute and wont harm the environment,etc. Dont use muriatic acid,etc. to ‘pickle’an A4 …. you’ll dissolve ‘metal’.
On a raw water cooled engine,it best to monitor with an Infrared ‘distance’thermometer. Record the IR temperature reading on various places along the cooling circuit. When you note a significant thermal rise from one spot …. time to ‘descale’. Example of a ‘distance’IR thermometer (pyrometer): www.amazon.com/KINTREX-Clear-Temp-IRT0421-Non-Contact/dp/B0017L9Q9C/ref=pd_bbs_sr_5?ie=UTF8ands=home-gardenandqid=1213332469andsr=8-5
FWIW:The exhaust manifold on the A4 and most Univeral Diesels is subject to “Slab Rust”. Large Plates of Rust may break off of the internal casting of the manifold and partly or fully block the water passage of the manifold. Best means to prevent ‘slab rust’is to **run the hell out of the engine** every so often;and,NEVER drain the engine/manifold and long term store the engine ‘dry’. Always for long term storage (months) is to fill the engine and exhaust manifold with a 50:50 mix of antifreeze and water. Buy ‘good’antifreeze;that which also contains anti-rust compounds.