Understanding 6V92 coolant flow

Topic: Understanding 6V92 coolant flow (Read 2551 times) previous topic - next topic

Understanding 6V92 coolant flow

September 08, 2018, 09:16:52 pm

Today I went down to SC to help Tony with his 94 GrandVilla U300 with a Detroit 6V92.
The repair issue today was water in is right front wheel hub. We pulled hub cleaned and inspected bearings installed new iner seal and new outer hubcap. That all done I checked his gas pressure on furnaces etc and it was good at 11 inches water column on my manometer.
He has had issues with engine temp and check engine light when running down the road. This is a side radiator coach. . I checked coolant level all good. He started engine and with my infra red thermometer I started taking temp readings. Cooling fans were running right from the initial start up. I am not familiar with the sequence of operation on these because my 91 is way simpler.
Anyway fans were both spinning. I checked temp at both heads where the coolant lines attach and go to the radiator. After about 30 minutes temps had risen and indicated t stats had started to open. Both coolant lines and bottom hose are all on the same side of the radiator. What I am trying to understand is the coolant lines going from the heads to the radiator both showed about 176 after we ran it and got temp stabilized. But where they attach to the radiator and back about a foot I was seeing about a 30-40 degree lower temp difference and a difference between the 2 lines of about 30 degrees. The bottom hose returning to the water pump never showed over 110 degrees. There is No over heating with coach idling. I am thinking he has a clogged radiator,because of the huge temp difference in the pipes going too the rad and the big return back to the waterpump. The thermostats must be opening as I see 170+ at the t-stat housings on the heads and I am seeing near those temps about halfway down the tubes going to the radiator ,at halfway point temp drops about 40 degrees.
Am I right to think rad is clogged slowing coolant flow,But enough to not overheat until under load? Also are the fans 1 speed on all the time or is there a high setting? How are these controlled?
Also there is a switch on the passenger side head that is broken. Tony will post a picture of it so we might understand what it did or is supposed to do. 2 wires hanging there . switch has a white plastic kind of cover but internal parts are gone.

Re: Understanding 6V92 coolant flow

Reply #1 – September 08, 2018, 10:01:45 pm

Are the radiator fins clogged up? They might need a goog washing out with a hose, being careful with the fins. I know some of these coaches have an H core radiator the flow is different on them.

Re: Understanding 6V92 coolant flow

Reply #2 – September 08, 2018, 10:16:31 pm

The fins looked good as far as I could see. I could see daylight through them and they did not look rotten.

Re: Understanding 6V92 coolant flow

Reply #3 – September 08, 2018, 10:54:46 pm

Did you say he is getting an occasional check engine light on the panel? Have you checked for codes as it will have one for each time the light comes on unless the 94 is different that our 93. It should go to partial power also.

Sounds like the fans are not going to high speed. Damaged switch?

If you have a electric screwdriver, you can pull a couple of strips and have the louvers out of the way in about two minutes giving you easy access to the outside of the radiator. You can then map the temps with your IR gun. I'm doing some Glas work on ours so have the louvers off now.

I don't have A-4765 but the library has an older schematic. I expect it's for the single fan model. Attached is the earlier version but may use the same color/number codes on the switch. Here is the link to our library and the schematic: http://www.foreforums.com/index.php?action=media;sa=item;in=3296#viewitem

Perhaps Ken can chime in as he had heating troubles with his about three years ago. Another Detroit had fan speed problems. Andy or was it Jerry? I know Andy just replaced his radiator.

Let me know and I can send a photo and wire codes for our switch tomorrow.

Tell Tony not to ever use the override switch on the dash!

Bet your glad you don't have all the complexity the later hydraulic system has.

Pierce

Re: Understanding 6V92 coolant flow

Reply #4 – September 08, 2018, 10:56:25 pm

Next question are the fans going to high when the engine gets hot?

Re: Understanding 6V92 coolant flow

Reply #5 – September 08, 2018, 11:12:36 pm

Sorry guys been trying to get photos posted but having problems with that. when i was driving it back from our last trip the temp got up to 210. i pulled it off the road and let it set for about 30 min. started it back up and temp was at 180. stayed at 180 the rest of the way home which was about 15 miles to my house. once i got home i let it run for another 30 min to see what would happen. stayed at 180 the whole time. on a previous excursion it did the same thing right before i got to my location , i let it run when i got there with the temp at 210 and it came back down to 180. both times the check engine light came on.

Re: Understanding 6V92 coolant flow

Reply #6 – September 08, 2018, 11:13:57 pm

I don't know if the fans go to high. Tony and I discussed that possibility. I dont know what controls the speeds. I saw a solonoid valve on the hydraulic line. I will look at the schematic and get familiar with the circuit .

Re: Understanding 6V92 coolant flow

Reply #7 – September 08, 2018, 11:19:51 pm

After you replace the damaged switch (it has three lugs but only two used) make sure the electrically operated hydraulic fan solenoid switch is working on the frame rail. Has a hyd hose in and out. I think a member made a fan speed reader by painting white on one blade. I think they go to high speed around 195 degrees but not sure.

Pierce

Re: Understanding 6V92 coolant flow

Reply #8 – September 08, 2018, 11:33:48 pm

Quote from: Tony – September 08, 2018, 11:12:36 pm

Sorry guys been trying to get photos posted but having problems with that. when i was driving it back from our last trip the temp got up to 210. i pulled it off the road and let it set for about 30 min. started it back up and temp was at 180. stayed at 180 the rest of the way home which was about 15 miles to my house. once i got home i let it run for another 30 min to see what would happen. stayed at 180 the whole time. on a previous excursion it did the same thing right before i got to my location , i let it run when i got there with the temp at 210 and it came back down to 180. both times the check engine light came on.

I let ours go to 210 max on grades but normally shift down/part throttle at 200 so you should not have a problem if it didn't go over that. Ours has no light except the warning light at approx 230 when the DDEC goes to partial throttle and then shuts down after 30 seconds. If your fans don't go to high speed, it won't overheat at idle but will under load, especially in hot weather.

With the engine up to temp, the fans move a lot of air so you can't mistake the speed.

The damaged switch should have a number on it. May be NAPA available. Have a plug ready when you unscrew the switch especially if the engine is warm. Probably 1/4" or 3/8" pipe thread.

Pierce

Re: Understanding 6V92 coolant flow

Reply #9 – September 08, 2018, 11:50:53 pm

Quote from: Pierce & Gaylie Stewart – September 08, 2018, 11:33:48 pm

I let ours go to 210 max on grades but normally shift down/part throttle at 200 so you should not have a problem if it didn't go over that. Ours has no light except the warning light at approx 230 when the DDEC goes to partial throttle and then shuts down after 30 seconds. If your fans don't go to high speed, it won't overheat at idle but will under load, especially in hot weather.

With the engine up to temp, the fans move a lot of air so you can't mistake the speed.

The damaged switch should have a number on it. May be NAPA available. Have a plug ready when you unscrew the switch especially if the engine is warm. Probably 1/4" or 3/8" pipe thread.

were is this switch located???
Pierce

Re: Understanding 6V92 coolant flow

Reply #10 – September 09, 2018, 12:20:19 am

Quote from: stump – September 08, 2018, 11:13:57 pm

I don't know if the fans go to high. Tony and I discussed that possibility. I dont know what controls the speeds. I saw a solonoid valve on the hydraulic line. I will look at the schematic and get familiar with the circuit .

Easy to test just jump 12v to the solenoid. The fans should jump to high speed. It's not a subtle change. Goes from blowing hard to blowing like hell! The solenoid is a pretty common part in hydraulics. Any hydraulics shop should be able to set you up.

BTW EVERY hydraulic shop I've been in and it's been more than a few have been the friendliest, most helpful places I've ever been! Can't say the same for many many truck repair shops I've been in.

350HP 6v92 are prone to overheating. They just can't fit a big enough radiator in there. Sorry to say but true. First off it's a 2 stroke. You are missing the cooling stroke of a 4 cycle. The good is that you get power on every stroke (and they sound so cool!) the bad is extra heat. Under most conditions it's no problem but at the extremes it's an issue. High temps and long steep grades are enough to overwhelm the system. Smart driving watching the temp gauge, down shifting, turning off cruise control, and using partial throttle all help keep temps down. This is not an engine for the mindless. It requires you to pay attention to your environment. In these extremes I think a mister system is a must. If you are on a mountain pass in high temperatures being able to hit a switch and actually control your temps is a god send!

Also be sure your temp gauge is reporting accurately by using a VMSPC. My temp gauge shows 200º my VMSPC shows 184º. VMSPC tells you the number you really need to worry about.

I've just spent the last few days driving across Tennessee. NE corner to SE corner. In mostly 90º temps. Only time temp has gone above 190º was on the long pulls. Only used the mister a couple of times. It's nice to have a safety net.

see ya
ken

Re: Understanding 6V92 coolant flow

Reply #11 – September 09, 2018, 12:26:15 am

To measure fan speed you can use one of these cheap tachometers. You place a provided reflective strip on the fan blade and point the device at it. Do idle and WOT. Post results here for group feedback.

Amazon.com: AGPtekÂ® Professional Digital Laser Photo Tachometer Non Contact...

see ya
ken

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Understanding 6V92 coolant flow

Reply #12 – September 09, 2018, 01:24:12 am

Discharge Temperature can't change much once in the hoses and flowing to a common header on the radiator unless one tsat is stuck closed which doesn't appear to be the case, IR guns get really funky when battery starts to get low.

Re: Understanding 6V92 coolant flow

Reply #13 – September 09, 2018, 07:44:14 am

Quote from: Old phart phred – September 09, 2018, 01:24:12 am

Discharge Temperature can't change much once in the hoses and flowing to a common header on the radiator unless one tsat is stuck closed which doesn't appear to be the case, IR guns get really funky when battery starts to get low.

New batttery in temp gun.
What I am having a hard time figuring out is why did I never see return water temp from radiator ever reach above 110 and why did the 2 coolant tubes from the t stat housings to the radiator only show 167 or so only halfway down the pipe. Where the hoses attach to the radiator the top hose was about 35 degrees warmer than the lower hose from the t stats.
The big bottom hose from the rad to the waterpump you could hold it with your hand.temp only showed 110.
Maybe we should have run coach down the road and got everything real good and hot and then taken temp readings.

Re: Understanding 6V92 coolant flow

Reply #14 – September 09, 2018, 09:42:18 am

Quote from: stump – September 09, 2018, 07:44:14 am

Maybe we should have run coach down the road and got everything real good and hot and then taken temp readings.

That would be the best way to get her warmed up. Hard to do just sitting in place. FOT used cardboard over the radiator to get mine up to temp.

BTW high speed mode kicks in at 187º on mine per the VMSpc.

see ya
ken

Re: Understanding 6V92 coolant flow

Reply #15 – September 09, 2018, 09:49:31 am

Yes on the test drive, rubber is a fair insulater and will take some time to equalize as the outside is probably getting washed by the fan. My cheap IR gun is also a little wall eyed and sensor doesn't quite line up with Lazer pointer, especially on round targets.

Re: Understanding 6V92 coolant flow

Reply #16 – September 09, 2018, 10:16:52 am

Duh! Just remembered that the hydraulic solenoid is a NO ie: defaults to high speed mode. I test mine by pulling the wire off the sensor. So if your sensor is destroyed you should be seeing high speed mode.

You don't need to drain the hydraulic oil to pull the solenoid. I pulled it and used a rubber stopper to plug it. You can pull it and put 12v to it. You should hear a click. I had to replace the coil on mine. You can buy the coil separate.

Attached is a pic of my solenoid before repair. Just remove the nut from the end and the coil will slide off. Well probably with some persuasion.

see ya
ken

Re: Understanding 6V92 coolant flow

Reply #17 – September 09, 2018, 10:21:00 am

Think many Foretravels have had heating problems starting with the smaller 5.9 Cummins with several recent posts on later coach overheating problems.

While every stroke is firing on a two stroke, the blower on top of the engine pushes massive amounts of air through the engine. And then the turbo even more on top of that. Just holes in the side of the cylinder for the intake and four exhaust valves to get rid of the heat. This is why a Detroit two cycle has exhaust temperatures about 150 degrees cooler than a four cycle. When is the last time you heard about a Detroit 2 cycle having a valve failure? They also don't crack exhaust manifolds with the frequency of other engines. You could use a U300 exhaust pipe for a huge leaf blower.

My guess is that the temp sensor/switch on the thermostat housing is what is damaged, those are the parts you are seeing and that's why no high speed fan.

Yes, the coach needs to go down the road to come up to temperature or pull the louvers and cover the radiator. Covering the louvers lets too much air by. Just idling is not going to do it.

The rear side radiator was a stupid, stupid idea for a GV with all the room and even the grills for a front radiator(s) with ram air benefits. I estimate hydraulic system looses about 60 HP in high speed operation. Lots of extra fuel needed and heat produced too. Plus, they never aligned the belt properly on ours and several others I have seen. Lost hydraulic belts and overheated engines are the result. I'm still angry about the poor installation.

Pierce

Re: Understanding 6V92 coolant flow

Reply #18 – September 09, 2018, 10:24:20 am

Ken,

You have the single fan and vertical radiator as I remember on your 1992 coach? Ours does not seem to default to high speed.

Pierce

Re: Understanding 6V92 coolant flow

Reply #19 – September 09, 2018, 10:36:33 am

Might be going down the wrong path here. I do get a little excited talking about coaches...

Not all U300 6v92's have dual speed fans. In fact I think most have single speed or more properly variable speed fans as the fans speed varies with engine rpm.

Very first thing to check it fan speed. Order the tachometer I mentioned earlier. Use it to get a baseline for your fan speed. I'm attaching a hand written fan speed chart FOT sent me. Hopefully you can find what your fan speed should be. If fan speed low you might be able to increase it by adjusting the pressure controller. It will be a about 5" by 5" aluminum block with several hydraulic hoses going to it.

BTW WOT stands for Wide Open Throttle. Took me a while to figure that out.

see ya
ken

Re: Understanding 6V92 coolant flow

Reply #20 – September 09, 2018, 10:43:54 am

Quote from: kenhat – September 09, 2018, 10:36:33 am

BTW WOT stands for Wide Open Throttle. Took me a while to figure that out.
see ya
ken

Ken, you always go down the right road!

I was not sure about joining the forum as I thought the group was super chauvinistic. Dish Washer (DW) is pretty bad. It took me quite a while to figure that one out.

Pierce

Re: Understanding 6V92 coolant flow

Reply #21 – September 09, 2018, 11:04:23 am

Ken,

You are right about the 187 degrees as my dash temp gauge is almost 10 degrees high.

Pierce

Re: Understanding 6V92 coolant flow

Reply #22 – September 09, 2018, 01:22:11 pm

Here is the broken switch

Re: Understanding 6V92 coolant flow

Reply #23 – September 09, 2018, 01:33:07 pm

And here I thought DW meant "Darling Wife".

Jim

Re: Understanding 6V92 coolant flow

Reply #24 – September 09, 2018, 03:05:41 pm

Looks like the one. Does it have a red wire and black wire close by? I don't have a part number. Since one of the connections is unused , I can post a photo of mine for the connections after you find one.

P

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