I have an 84 F-250 6.9L that won't blow hot air. Before I go spend money on a heater core or a thermostat I want to know what it's more likely to be. As the weather got colder (in the last week or so) the needle would read colder and colder every day and the heater would blow colder and colder every day. Fluids are all good. My glow plugs don't work and neither does my block heater so she is an ether baby if that affects anything. Thanks everyone!

 

Sounds like the thermostat being stuck open to me.

 

I agree with Macrobb - My coolant temp was staying low even after 65 miles of highway driving at 45-60 mph when it was 50 degF outside. I removed the thermostat and discovered that the rubber part was significantly deteriorating so coolant was probably leaking past the thermostat- I didn't bother to even look closely to see if it was stuck open or test it in boiling water... I just threw it into the garbage can.

In addition I thought that my temperature gauge did not work so for a couple of months I tried different things, a few new temp senders and THEN I discovered that the gauge actually DOES WORK, it's just that the engine wasn't getting warm enough to show noticeable movement on the gauge.

I have a number of things apart in the engine compartment and the new Motorcraft thermostat will be in and the engine running again in a few more days ... then I'll know with more certainty if the thermostat was the cause.

You should certainly get the glow plugs circuit fixed- test and replace the GPs if necessary, and or the controller or bypass it with a manual glow plug switch (push button).

Using ether / starting fluid is not a good idea. If the starting fluid is manufactured especially for cold starting diesel engines, that should be safer (or other spray options I have heard of). If you like the truck Fix It.

 

The behavior of your engine temperature gauge, running cooler as the outside temperatures dropped, would indicate a thermostat problem, like stuck open, rather than an obstructed heater core/or the lines going to it. (In my perception).

If the heater core had a small leak you would still get heat and probably smell the coolant unless its a really bad leak so no heat coming from the heater core because the heated engine coolant is all draining out.

 

PS: 2 things- 1) The thermostat is not nearly as simple to change as on most gas engines so you'll need proper instructions, preferably with photos. It CAN be done wrong with some risk of damaging other parts.

I found one tech article at Oilburners forum entitled 'Thermostat Replacement Tech 101 Pictutorial', where the writer did a very nice presentation but he did it WRONG, risking damage to other parts. I noticed this while I was originally following his directions. I had to change course and do it differently than he showed. I further confirmed that by looking up the procedure in the official Ford Shop manuals (which I should have done in the first place and avoided extra work that became necessary to avoid that writer's mistakes). I'll be getting back there to straighten him out one day very soon - 6.9L or 7.3L should make no difference on what that writer missed.

I can post the instructions from the 1987 Shop Manuals for you tomorrow night - should be the same on your truck, if not you are covered anyway*. Then in two days or so I can post photos of two* different ways to safely do this job.

Second concern is Engine Coolant. It MUST have SCA additives to protect against cylinder wall cavitation. Ask the previous own if that owner changed the engine coolant/when and if FOR CERTAIN an SCA additive was in the coolant (SCA Pre-charged) or IF the SCA additives were added to a non-SCA-precharged coolant. You can ask what coolant was used.

If you can't find out that information from the P.O your coolant needs to be tested with test strips OR it may be time for a coolant flush and fill anyway so you can BE SURE that you have the right coolant with SCA protection.

Lastly, I hope that you have a sheltered area to do this work. It's getting cold in Idaho!

 

x2

Also, make sure you only use a Ford/Motorcraft thermostat. The aftermarket ones fit, but don't work. Motorcraft ones can be found on Amazon for pretty cheap, possibly locally. I'd try and find a link for you, but in a rush to get out the door... if you search on the forum its been posted before.

 

You can also use a HD ELC coolant. It seems to work just fine, and is recommended for the newer engines. I used the Zerex HD ELC, which I picked up at Napa. It was on sale for about $14/gal, IIRC.
Make sure to mix with distilled water. Don't want to use tap water!

 

Do see my 2 simple questions at the end, Macrobb. This post is long but hopefully informative and worth reading.

I WISH that I could say the same thing about Extended Life Coolants, (ELCs) - that they are fine to use in IH/Navistar IDI diesels! Life would have been so much easier for a couple of months! During that time I had to read the whole history of engine coolants and I also read every technical document on-line that I could find on ELCs and SCA coolants/SCA additives, plus every diesel coolant (brand) website for any technical information . I was trying to confirm that ELCs are in FACT OK to use in these IDI's.

The reason I did this is because there is some evidence to indicate that they are *not OK* and I found no qualified evidence that they are OK, not even from the the coolant brands websites- as you mentioned they are "for NEWER diesel engines" than these Navistar IDI engines. Typically, if I remember correctly they state Newer diesel engines from around 2006 onward.

There MUST be a reason why the specify "Newer" in that general time-frame rather than "ALL" diesel engines.

I learned that coolant technology, the chemical formulations, manufacturing processes along with the numerous different additives used is so incredibly complex that you would have to become an engineer specializing in coolant formulations to understand the full complexities of it. I never wanted to become an engineer specializing in engine coolants so having to read all of that to find a simple answer to this question really sucked!

This all began in a thread started by Josh_Bear in Washington State about coolant filters and also discussed the new ELCs.

I thought 'WONDERFUL ELC IS WHAT I WANT!" While I was looking into this further I discovered a topic in a Power Stroke forum (here at FTE) that stated within, seemingly very credible evidence (from multiple sources) that ELC's should NOT be used in pre-1999 Power Strokes. In another topic related to coolants where this was discussed, this caution was by logic extended back from pre-1999 Power Strokes to include IDIs.

It was stated that ELCs can cause cracked injection cups- a very expensive repair. I don't see how a coolant could cause that but I don't have specific knowledge of such problems in Power Strokes bu after reading about problems in the 6.0 nothing would surprise me - and I have no intention to research that injection cup issue further

Another problem which I found in my searches and is CONFIRMED is that the Organic Acid Technology (OAT) ELCs did eat (or degrade) seals and gaskets many of which contain silicone in their manufacture and this is the case with IH/Navistar IDI diesels. I think that Navistar issued a warning on this in the mid 1990s?) I think that was discovered after about 2 years on the market. As far as I am aware OAT based ELC coolants are still being sold and how they are labelled I don't know. There were 3 or more significant changes in coolant manufacturing technology after the OAT coolants.

You probably do not have an OAT coolant Macrobb.

When a coolant label states "For Newer Diesel Engines" and especially if somewhere in their literature it gives a time frame like 2006 and up, does that mean NOT for older diesel engines? In some cases there could be a technical reason for that and they are covered from any liabilities for older engine designs

I finally determined that the only way to get a qualified answer to this question is directly from an Engineering Department at Navistar, hopefully still having some engineers who are very knowledgeable about the IDI engines.

I don't think Ford or many other entities (like California Gov. etc.) care at all about the service of these trucks and would prefer that all of them be sent to the crusher. Navistar is probably the exception because this IDI helped a great deal to build their reputation. I had intended to craft an email to Navistar and try to get an answer to this question from the Engineering Dept.

So, I must say that the ELCs and their technologies are extremely attractive. A video presentation was posted in Josh_Bears topic which was very illustrative of how that coolant worked (anti-cavitation for example) and very very impressive (still though at face value like most advertising but did exhibit the technology).

It may well be that some of the ELCs for diesels or most of them ARE OK for use in IH/Navistar's IDI engines and I do hope that turns out to be true but until then, I KNOW that the SCA additives do work and that is what is still specified for this engine. If there is an update to those specifications that approve an ELC I would sure like to know about it and then I could recommend as well as USE that ELC.

By the way if you didn't catch this in what I wrote above, ELCs are NOT all the same, different brands from different manufacturers use different additives and there are a bunch of those different additives - some are proprietary with patents.

All of this just to try to answer a simple yes or no question.

Until then, the only coolant that I can recommend and know that it is secure information is the SCA coolant.

Questions:
BY THE WAY, Macrobb, 1) what is the color of your new ELC coolant?
2) Have you, or can you test this new coolant with an SCA test strip if you have any? I would like to know what it reads on your ELC coolant

I ask because I just drained an obviously new coolant from my truck, it was a light green color, probably changed out by the previous owner. It may well have been an ELC because I know for sure that the previous owner would have at least used a Diesel Engine Coolant and thnk most of those are ELCs. The new SCA test strips I used showed ZERO SCAs and that is why I am changing it now- along with an acid based system flush with new thermostat (the old one was really shot, the rubber part was deteriorated and probably the original t-stat - I should have taken a picture of it but I threw it straight into the garbage can!)

Doing other work under the hood right now also, so I have to get outside NOW ASAP and get this work done in the next 2 days before it starts raining again - in cold weather!

I always like to read all of your posts, MacRobb, I don't always agree (ie: messing with injection pump timing as a first resort for certain smoke issues- even though you might be right) but it's good to read posts by someone who is always doing some kind of work on these engines and major work at that.
I do have a somewhat personal question, and you don't have to answer it: Do you work in a machine shop? I got that impression for some reason.

Thank you.

 

lilraven96, WHERE ARE YOU?

I've seen two topics you have started with NO REPLIES from you. I went to your profile to send a private message in case you are not receiving e-mail notices of replies to your topics (SPAM filter for example) but I saw that you were viewing this topic at the same time.

I had offered to post the thermostat replacement procedure from the 87 shop manuals along with photos but would I be wasting my time to do that? I don't know what your situation is or what you intend to do.

BTW, what do you intend to do? including the glow plug issue- which is much easier than the thermostat replacement but costs more.

 

My understanding is that all ELC coolants use OAT. If you look at the product info sheet, it does say it.
Also, I see nothing on the Zerex package or sheets saying that it should only be used with newer engines. I'm thinking that the modern formulation is probably safer for seals than earlier stuff.
My view is that, unlike Powerstroke engines, our IDIs have very few seals in contact with the coolant. There are a couple of O-rings in the oil cooler, water pump seal, and a few gasket seals. That's all. Very little to go wrong.
In the info sheet for the Zerex HD, one of the tests is for "nometals", and it says "no adverse effects". I have no way to prove that this stuff is perfect, but I think the risk is pretty darn low.
I originally decided to run Zerex G05 coolant, and did so for over a year. But this apparently isn't a good enough coolant for proper protrction. It's also an OAT-based ELC.

It's red.
I have a bunch of test strips, but none at hand.
Yes, "diesel" coolants are generally ELC, though they could just be pre-charged with SCAs.

I try to respond to topics with what I currently think is the most appropriate option, even if it's not the most conservative. In the case of pump timing, I've poked, prodded, removed, reinstalled, re-sealed and otherwise messed with several different IDI IPs, and use several trucks. If there's one thing that's always caused me problems or created major changes in how an engine feels, it's timing.

Yes, I do. I have a 2-year degree in precision machining, and got a job at an aerospace machine shop right out of school. That being said... I kinda got moved into IT(which was my hobby) at that machine shop due to it being more valuable to my employer(despite being entirely self taught with no credentials). I love making things, even though I don't get a chance to use a mill or lathe as much as I'd like.

 

Thank you for your time, Macrobb!

I have to agree with all of your reasonings, the most important being that the current OAT coolants use more recent Organic Acid Technologies and formulations (This 'evolution' of OAT coolants was indicated in some of the technical documents I had read).

After a bit more reading and all things considered, I now accept that the modern diesel OAT coolants are safe to use in the older IDI engines but I'll still be careful of which one I choose, look up specifications/test results and approvals* and compare those when that time comes but that should be fairly simple.

The next technology following OAT was NOAT (Neutralized Organic Acid Technology) ELCs such as PEAK 'FINAL CHARGE NOAT' which is also sold world-wide. Based on some wording in the respective warranties for OAT based PEAK FLEET CHARGE GLOBAL' vs PEAK FINAL CHARGE NOAT, the OAT ELC apparently lasts longer so by that measure at least, the OAT based ELC is better.*They are implying 1 million miles on the OAT based ELC and 750k on the NOAT ELC- Purely Advertizing/marketing propaganda in my opinion. When I've read the really fine print those advertising claimes are virtually meaningless.

There is at least one newer technology after NOAT and I don't remember what it is called. LOTS of changes over the years in coolants for gasoline engines and in Europe they have some different views on coolants for diesel and gas engines.


For now I'll use the Peak FLEET CHARGE SCA Pre-charged which I have right here and if I install a Penray (SCA release) coolant filter in January and change it every 18 months this SCA coolant is also considered a "Life Long Coolant." I'll probably use this coolant for 18 months or LESS (pobably less than a year) and then convert to the OAT ELC. Keep the filter but not an SCA release filter.

One possible reason why there is no specific answer out there for this coolant question may simply be: I don't think Ford updates specifications on vehicles and individual components (including fluids) on anything that has been out of production for 20 years, at which time component of those vehicles are deemed obsolete. I think the 'obsolete parts that remained on the shelves get sold to aftermarket parts dealers who sell them as OEM parts.

With no updated Ford coolant specs for the IDI trucks (all more than 20 years old) no outside coolant manufacturer can legally make the claim that their later non-SCA ELC coolant formulations are fit for use or approved for use by Ford Motor company in Ford IDI diesels. In fact I have not seen a single instance where the major label ELCs have a Ford Motor Company approval. I wasn't watching closely for that though. Maybe Ford only wants us to buy Ford/Motorcraft coolants and parts. Who'da thunk they would do that??

This may also be the reason why PEAK doesn't discontinue their SCA Coolant instead of just advising everyone to use their ELCs (which they also do!) This way they can maintain sure sales to IDI owners and apparently they value that market.

Side note: I went through machinist school full time (8hrs per day) for one full year (12 months) via a community college with technical programs - I didn't work as a machinist although what I learned has been very valuable to me in so many other things I do. I try to get machine tolerances in everything I do including 'rough' carpentry. I was also a very good draftsman and competent pattern and layout draftsman which I loved doing for the technical challenge- Simply put, I like everything to fit perfectly (as much as is practical) - I often have to draw a line and say 'good enough' or I'd never get things done almost always trying to find a better way and then beyond that an even better way, etc.

IT? Self taught also but no longer a big interest. I was obsessed with computers for years and I wish I had never loaded Windows onto my computer- I was having fun with MSDOS!. I was brainwashed by Microsoft like most other people were and I wasted the best years of my computer life with closed source Windows and I am actually very bitter about that. I wish I would have worked with LINUX from the start an THEN I really would have learned a tremendous amount about software and operating systems etc. and would probably be a competent software developer.. (as a hobby) - no longer interested. Hardware of course is simple.

I finally did switch to linux about 12 years too late and seriously, you can't imagine the incredible sense of freedom - not having to deal at all with malware viruses etc. as in Windows, never having to read another article about the latest windows threats, etc. I never had a problem with windows malware because I was very security conscious but that also wasted a lot of time trying to keep a windows machine secure. But I was constantly fixing other people's infected machines - probably earned about one penny per day at best because it was always for poor, disabled or elderly people or relatives. I still do it but I hide from them.

This is long because I write too much when I am tired and also since the Original Poster (OP), lilraven, hasn't returned there is not much else to talk about in this topic.

I hope he didn't get lost and run out of ether to start his truck in some cold remote area.

He is over in your territory too, Macrobb.

Maybe I will send a private message to lilraven