Importance of Engine Operating Temperature

[markopolo]

Thanks for the cardboard tip. I couldn't see a way to do it exactly like that but was able to make to cardboard panels that fit in slots entering from the top. I might be getting 75% coverage with those panels. They're secure & easy to insert and remove. A $3 black anti-fatigue diamond plate look mat made for a not-to-bad-looking grill cover. There was no significant change during an idle test. I'll wait for a nice dry day to do another highway run.

8 hour estimate to remove/replace the coolant crossover housing

At this point I'll do nothing. I'll have the parts (got the AC Delco t-stats today) ready to go to get the job done when I find the right place to do it. I don't drive it much if at all during winter so I'll take the time to find out what other hard to get to items should be replaced and do them when the t-stats get replaced. My best option will be a smaller shop that charges by the hour and not by the job.

The dealer I went to charges by the job as a minimum - if they say 8hrs at the beginning based on what the database says the you get billed that rate as a minimum & billed more if it takes longer. It's partly understandable when you realize they've reserved that bay time slot for the repair. It does means they won't get this job though.

[dknightd]

Originally Posted by DCHitt

So far I have been changing the oil when the message pops up on the dash. I do think I will go to synthetic oil. Don't know what a "taxi regimen" would be.

Just catching up on my reading here. I don't know if this has already been addressed.

I don't know what triggers a message on your dash to change oil. It could be so many different things.

The "taxi regimen" is my name for severe duty. Lots of stop and go. Lots of idle time. Lots of start and stop engine. In the old days they would have recommended oil change intervals for regular and severe duty. Most car usage these days falls under what I'd call "taxi" or "severe" use.

Occasional running of an engine to charge the batteries without driving anywhere is VERY severe duty. The oil never really reaches proper temperature to evaporate contaminants. The engine probably does not get to operating temperature, so tolerances will not be ideal. And obviously millage becomes irrelevant if you are not driving.

If I was running an engine just to charge batteries (something I am considering) I'd run above normal idle speed. I'd measure the alternator output, and monitor fuel usage, and set my high idle to maximize alternator output for the fuel used. Obviously this target rpm will be different for every engine and alternator combination.

[dknightd]

Originally Posted by markopolo

I just got some motivation. I got the service dept to look up the job specifics and it comes to 5 to 6 hrs in the shop. With tax and parts it could get to $800 here and I'm not exaggerating. 90% of the time involved is removing and later replacing everything that is in the way. I'll have the AC Delco t-stats tomorrow anyway so today I'll try to figure out what that pipe is that's in the way and blocking access to one of the four bolts. If I can move that pipe to get to that bolt then I can DIY.

I'm not familiar with your engine, but, that "lower pipe" looks like a wire to me. It could probably be easily moved out of the way. The shop hours probably include removing and reinstalling things you have already done. i.e. dog house.
On some vans it might be easier to drop the engine to gain access. This post is changing from general questions about operating temperatures, to specifics about replacing your thermostat(s)

[dknightd]

Originally Posted by markopolo

Thanks for the cardboard tip. I couldn't see a way to do it exactly like that but was able to make to cardboard panels that fit in slots entering from the top. I might be getting 75% coverage with those panels. They're secure & easy to insert and remove. A $3 black anti-fatigue diamond plate look mat made for a not-to-bad-looking grill cover. There was no significant change during an idle test. I'll wait for a nice dry day to do another highway run.

8 hour estimate to remove/replace the coolant crossover housing

At this point I'll do nothing. I'll have the parts (got the AC Delco t-stats today) ready to go to get the job done when I find the right place to do it. I don't drive it much if at all during winter so I'll take the time to find out what other hard to get to items should be replaced and do them when the t-stats get replaced. My best option will be a smaller shop that charges by the hour and not by the job.

The dealer I went to charges by the job as a minimum - if they say 8hrs at the beginning based on what the database says the you get billed that rate as a minimum & billed more if it takes longer. It's partly understandable when you realize they've reserved that bay time slot for the repair. It does means they won't get this job though.

Sounds like you know what needs to be done, and already have the parts. Some engines this is a trivial job. Some engines not so much. I'd avoid running the engine till you know the problem was fixed.

[markopolo]

Hopefully, from the specifics I'm posting, some general ideas will be useful. My next highway run should produce a higher temperature. It's well above the sustained low temperature that would result in a DTC code.

The cooling system with two auxiliary coolers on this van is very efficient. Things looked really good this past summer when towing. We're at the freezing point here now.

I'm a fan of increasing the idle speed on a diesel. - http://www.classbforum.com/forums/f8...-mod-2187.html - It can result in increased Air Conditioning, increased Electrical Output and increased Vehicle Heating for stationary operation. I think you need to observe the results in specific vehicles and at specific times though as it also increases fan and water pump volumes. Idle speed on my van will automatically ramp up a bit in response to alternator load independent of my use of the idle speed control switch.

[markopolo]

Blocking the radiator did help. The dash gauge peaked at 176F with the outside temperature at 34F.

The steel pipe that blocks access to the two lower bolts on the thermostat cover is the collection line which is part of the fuel return system. But for that line I would have already replaced the two thermostats.

return fuel line.jpg

Next up is tracing that line. The attachment points were not visible to me from the front. Ideally I'll find a way to permanently lower it just a bit.

I tested the new AC Delco thermostats & confirmed that they both open at near (just below) the boiling point of water. They both closed as soon as that water temperature was reduced a bit.

[markopolo]

Just updating an old topic in case someone ever stumbles across this topic looking for some help with replacing the two thermostats in a GM van with the 6.5L turbo diesel.

You have to remove a lot of parts to get access and even after that you can't get a line of sight on one of the four bolts.

- drain coolant
- remove air intake box
- remove belt
- unbolt a/c compressor move away/over keeping it as level as possible
- remove passenger seat for space
- remove some dash panels
- remove console
- remove air duct
- remove doghouse
- remove air intake tube & cover hole so no debris gets in engine

Coolant reservoir removal seems optional. I ended removing only because I dropped a bolt.

Disconnecting the battery ground is usually prudent.

Bolt removal is from the cab side & thermostat replacement is from the front of the van.

You'll need 30" or so of ratchet extensions. I used wobbly extensions. They're made purposely so there's a fair bit of articulation and I think that helped. Access to the two lower bolts (you can't see one of them) is through/under the intake manifold crossover. That seemed to give the best path and angle so you can put enough torque on the bolts and not have the socket slip off..

When putting everything back together refill the coolant while the air intake box and tube are still off. That gives you access to the air bleeder valve.

It's no wonder that the dealer quoted 6 hours labor. It took me all day with no helper. Lots of in/out of the van trying to get the socket line up & get it on the bolts. Some of that time was wasted looking for a bolt I dropped. I never found it as it is near impossible to access much near the center of the engine.

I took a short slow speed drive into town (to buy a bolt to replace the lost one) and coolant temp got to 180F fairly quickly and peaked at 186F. Much better.

I had previously blocked off the grill to help keep operating temps up and that worked for a while. During colder months I also added some cardboard in front of the radiator but finally got an insufficient operating temperature code so I could not put the job off any longer.

[booster]

That has to be one of those "what were they thinking" kind of design!

Kind of like having to pull the engine to do routine maintenance items on some of the mid engine exotics.

[markopolo]

Even with all that it wasn't easy. It was probably a good enough design for trucks but they really should have made the thermostat housing bolts accessible from the front for vans. I'm just glad it's done! It was on my to do list for way too long.

[booster]

Originally Posted by markopolo

Even with all that it wasn't easy. It was probably a good enough design for trucks but they really should have made the thermostat housing bolts accessible from the front for vans. I'm just glad it's done! It was on my to do list for way too long.

IIRC, you had mentioned that the dual thermostats was to combat overheating from low flow. If it had only one thermostat would it have had a lot less space eating extra stuff in the way and been any easier?

[markopolo]

It probably would have been a bit easier if it had single tstat housing. The coolant crossover body would be the same basic size no matter if one or two tstats so if just one tstat in the same space then lots more room for fingers or a tool.