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TurkisMafia Samba Member
Joined: August 21, 2019 Posts: 186 Location: Sarasota, FL
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Posted: Tue Dec 07, 2021 2:49 pm Post subject: Cyl Head Temps Way too hot - '78 EFI Automatic |
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Hi Guys,
The heads on my motor gave way recently, so we did a full top end rebuild. I did one 300 miles round trip after the fresh build, and it just felt to me like the motor was hot. It did not fail or show any symptoms, but it felt and smelled hot. I since parked the bus and got the parts together for a CHT gauge.
I installed a TSC (the sensor connection) 4 channel CHT and used the dakota digital 18' termocouples.
Barring a gauge issue, it would appear I was correct. Just sitting idling, the #3 got up to 400, and a quick gentle run around the block produced temps in excess of 450.
All new wiring harness, new injectors, and a full test on the AFM and computer... everything appears to be functioning normally.
What can I do about this? I already fear I could've done damage to the new heads and rings. We checked the timing and set it to factory specs... and then tried retarding the timing to cool it off. With the timing backed down, there was a noticeable loss of power but no help on temps. Has anyone had success cooling these fuel injected motors down?
Thanks!!
_________________ 1961 Turkis Sedan, 1641cc
1963 Turkis Ragtop, 1200cc
1963 Turkis Vert, 1200cc
1963 Turkis Single Cab, 1600cc
1964 Turkis Standard Walk-Thru, 1641cc
1978 Westfalia 2.0L EFI Automatic
Turkis Mafia
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Sunny Sarasota, Florida |
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BUSBOSS Samba Member
Joined: January 21, 2009 Posts: 2161 Location: Northern California
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Posted: Tue Dec 07, 2021 3:04 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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All tin in place? Engine foam seal? Flaps and thermostat working correctly? _________________ All the redemption I can offer, girl, is beneath this dirty hood
1976 Westfalia
1970 Karmann Ghia Convertible (sold - but not forgotten) |
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TurkisMafia Samba Member
Joined: August 21, 2019 Posts: 186 Location: Sarasota, FL
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Posted: Tue Dec 07, 2021 3:06 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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BUSBOSS wrote: |
All tin in place? Engine foam seal? Flaps and thermostat working correctly? |
Yes, tins are all there as well as the foam. We hooked the thermostat back up per the manual, but that was one thing we brought up that needs to be checked tomorrow. _________________ 1961 Turkis Sedan, 1641cc
1963 Turkis Ragtop, 1200cc
1963 Turkis Vert, 1200cc
1963 Turkis Single Cab, 1600cc
1964 Turkis Standard Walk-Thru, 1641cc
1978 Westfalia 2.0L EFI Automatic
Turkis Mafia
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Sunny Sarasota, Florida |
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22670 Location: NYC/Upstate/ROW
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Posted: Tue Dec 07, 2021 3:11 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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COnfirm with a non-contact IR measurement, then move to AFR measurements to find out why you are as lean as shinola _________________ .ssS! |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Dec 07, 2021 4:15 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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the cylinders the farthest from the fan are hottest. Make sure that the fan is clean and doing its job. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Dec 07, 2021 4:15 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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duplicate post _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin
Last edited by SGKent on Tue Dec 07, 2021 10:12 pm; edited 1 time in total |
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my59 Samba Member
Joined: August 13, 2003 Posts: 3793 Location: connecting the dots
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Posted: Tue Dec 07, 2021 7:34 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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Heads gave way, what was wrong with them might be a lead in here.
Air fuel mix if retarding the timing to say 28 doesn't drop theTemps
What's ambient? I can run 400 at 65mph when it's 95 out, or run 400 at 80 plus when it's 40. _________________ my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
our79: sunroof bus w/camper interior and 2.0 FI
Other:'12 Jetta, '77 Benz 300D, and a 74 MG Midget. |
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vacca_rabite Samba Member
Joined: July 04, 2021 Posts: 72 Location: PA
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Posted: Wed Dec 08, 2021 8:16 am Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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my59 wrote: |
What's ambient? I can run 400 at 65mph when it's 95 out, or run 400 at 80 plus when it's 40. |
Heads should never get to 400 at idle under no load. This isn't a question of ambient temps.
My guess is that thermostat isn't working or the flaps have failed closed. Something is blocking airflow between the fan and the heads.
Zach _________________ 1972 T2 Bay Westy in restoration
1976 Porsche 914
196? Empi Sportster Dune Buggy |
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TurkisMafia Samba Member
Joined: August 21, 2019 Posts: 186 Location: Sarasota, FL
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Posted: Wed Dec 08, 2021 1:41 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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Update to all: apparently I damaged all 4 probes going into the head. I knew they were fragile and attempted to be careful but…. Guess I need to replace and figure out a more careful way to install. The oval shape was allowing exhaust gas to overheat the probes. That being said, in inspecting the bellows on the thermostat, it would only expand from 33mm cold to 39mm when heated with a torch. Rat well says it should expand to 55mm when full hot. Flaps may not have been opening all the way on top of all this. _________________ 1961 Turkis Sedan, 1641cc
1963 Turkis Ragtop, 1200cc
1963 Turkis Vert, 1200cc
1963 Turkis Single Cab, 1600cc
1964 Turkis Standard Walk-Thru, 1641cc
1978 Westfalia 2.0L EFI Automatic
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borninabus Samba R&D Dept.
Joined: May 18, 2006 Posts: 4539 Location: Arizona Highways
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Posted: Wed Dec 08, 2021 3:42 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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you can't really install thermal couplers (ring terminal style) under the spark plugs without machining the boss in the head a bit bigger to accommodate them. it's only a matter of time until they distort and no longer seal when changing plugs.
take a look at where VW thought was a good place to measure head temp. there's a spot for TS2 on both heads, BTW. it may "not be as accurate" as under the plugs...but the temps you will see are much less stressful, will change almost instantly with the throttle and as with any other gauge, can still be used for trending.
sounds like you have some cooling issues to get a handle on first though. _________________ 88 Van WBX, A/T - 13 JSW TDI 6M/T - 2012 Touareg TDI Sport |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Thu Dec 09, 2021 8:44 am Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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Let the sender act as a sealing washer. The standard spark plug washer is beveled, and it will expand the ring. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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LouFilia Samba Member
Joined: January 22, 2015 Posts: 77 Location: SLO, CA
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Posted: Thu Dec 09, 2021 10:58 am Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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SGKent wrote: |
Let the sender act as a sealing washer. The standard spark plug washer is beveled, and it will expand the ring. |
This
If it's all four or three of four, I'd bet this is the cause. _________________ '78 Westy (P22), 2.0FI (GE), 4speed (CP), thought I was buying a VW, ended up with a Bentley. |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2713
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Posted: Thu Dec 09, 2021 11:11 am Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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to the OP and others, id always suggest just using the Dakota Digital setup under the #3 plug. It's what most others have and then you can at least do a better Apples to Apples comparison on numbers. Otherwise what you have is really only good for trending. |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21520 Location: Oklahoma City
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Posted: Thu Dec 09, 2021 12:05 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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Danam404 wrote: |
Update to all: apparently I damaged all 4 probes going into the head. I knew they were fragile and attempted to be careful but…. Guess I need to replace and figure out a more careful way to install. The oval shape was allowing exhaust gas to overheat the probes. That being said, in inspecting the bellows on the thermostat, it would only expand from 33mm cold to 39mm when heated with a torch. Rat well says it should expand to 55mm when full hot. Flaps may not have been opening all the way on top of all this. |
Ok....a couple of things:
Good detective work!
So the HIGH temps that high could probably ONLY be from exhaust gas leaking.
The thing about thermocouples...TC's....is that they will not read erroneously. If they are reading high...something IS getting that hot at the hot junction point.
If one were reading excessively low when fully warmed up...one would think that the TC wire got crimped hard enough to bring the two wires together somewhere upstream creating a NEW hot junction in a colder environment.
I have never thought that putting the TC ring terminal UNDER the sparkplug....was good. NEVER.
1. It makes ....as you have found....for iff or poor sealing.
2. It makes the TC easy to damage when you have to remove the spark plug.
3. While I do I agree that generally the spark plug BOSS area will "usually" be the hottest part of the combustion chamber casting area because that is where the flame front propagates from.....having the TC ring actually contact the sparkplug.....is kind of stupid.
If you have ever run a sparkplug in a sparkplug testing clamp with a coil system just for giggles and grins....and run it for about 10 minutes....the sparkplug gets pretty damn hot all by itself. Thats with the sparkplug not screwed into a cylinder head
And....while the cylinder head makes a good heat sink to take the heat out of that plug that is generated by 10-20,000 volt arc 25-30 times per second....the head is only a god heat sink WHILE its cooler than the sparkplug. Once the head heats up to as hot or hotter than the plug....its more probable that the sparkplug becomes more of a heatsink for the head.
So who wants to know what the sparkplug temp is? No one. We want to know what the head temperature is NEAR...very close to....the sparkplug boss.
So long ago I tried a few things to get the TC out of contact with the sparkplug....if for no other reason than to make changing/checking/gapping plugs not a chore...and to prevent the damn leaky gasket thing.
I did find that in spring and fall weather average CHT readings were about 15-20 less than they were when the TC was in actual contact with the plug...except in hot weather when pretty much the same across the board.
You can see the mod I did in this thread. At some point I will do a complete how to for it.
https://www.thesamba.com/vw/forum/viewtopic.php?t=752545&highlight=
In reality.....you can do something like this as simply as taking the copper ring terminal off the TC. You will find a very small welded bead on the end of the wires. Its usually about 1/32" to 1/16" in diameter.
You can mark where the plug gasket is with a marker. Unscrew the plug. About 0.050" away from where the gasket will sit when the plug is installed....drill a small hole in the head about 1/16" in diameter and maybe 0.050" deep. Just a small pit. Stick the bead of the TC in the hole and fill it with JB weld. Cut a small slot in the sidewall to run the wires away from the plug.....and that can work just fine. Thats all it takes even though there are better ways. Ray |
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vacca_rabite Samba Member
Joined: July 04, 2021 Posts: 72 Location: PA
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Posted: Thu Dec 09, 2021 12:18 pm Post subject: Re: Cyl Head Temps Way too hot - '78 EFI Automatic |
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The last few posts are on fire.
To use the ring terminals you need to cut a groove in the boss of the heads so that the terminal and the wire don't get pinched. You can use a dremel for this, or even just a round file.
You need to take the washer off the spark plug and use the ring terminal as the washer.
As to the head temp boss, yes that can work. Yes the temps will be lower. But its not the location I would use on my engine. I actually monitor both under the spark plug and at the head temp boss. On my engine (Microsquirt EFI) I monitor "coolant" at the head temp boss. Its used for warmup enrichment. I run a Dakota digital on Cyl3, a mere couple centimeters from the head temp boss.
There is ~ 50 degrees difference between the two until the engine is COMPLETLY heat soaked. By the time the boss is showing 400 you engine has really been cooking for a good long time.
Zach _________________ 1972 T2 Bay Westy in restoration
1976 Porsche 914
196? Empi Sportster Dune Buggy |
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