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[LairdScooby]

What temperature should be shown when the engine is hot on the temperature gauge? Despite a new thermostat, mine struggles to ever get above 60 apart from once when i got stuck in traffic in London a couple of months back and it eventually crept up to 100 and the heater actually started blowing hot air! Normally it's tepid/lukewarm.

The 'stat (if memory serves) is an 88C one so i would expect a bit higher than 60 on the gauge and a much better heater output. Before i changed the 'stat, it struggled to get much above 40C so there was obviously a problem.

My gut feeling is there is a problem somewhere so coolant can get past the 'stat (possibly 'stat housing leaking past the 'stat?) but i didn't check it when i changed the 'stat (should have done i know  ) but is there a common cause of over cooling on these? I've been spoiled for a long time with electric cooling fans although i did have a Volvo 740 that also used a "vicious" cooling fan (viscous) but even that warmed up to full temperature (halfway up the gauge) within about 5 minutes, even in icy conditions.

With the prospect of cold weather coming and wanting to use the Jeep as my weapon of choice for most journeys, i want (and need!!!) to get the heater output sorted. I know the engine in the Jeep is nearly twice the size of the Volvo and about 1.5 times the size of my other two so maybe it will be slower to warm up but even on long journeys, it never gets above 60C unless stuck in heavy town/city traffic and even then it only hit the 100C mark for about a minute or so, dropping to 60C as soon as the speed got above walking pace.

Any ideas/known trouble spots/work-arounds/fixes for this? Thanks in advance!

[Jonny Jeep]

Should be pretty much straight up on the guage. Thermostat spec is 195f so 88C should be close enough. Maybe it's stuck open

Sent from my D5803 using Tapatalk

[Brynjaminjones]

I think undercooling is usually the problem with XJs!
My temperature used to go from just below to just above 100 on the gauge, but never budges from just below 100 with a new cooling system.
I'd guess it's a bad thermostat.

Sent from my HTC One M8s using Tapatalk

[LairdScooby]

At the risk of sounding facetious, can you define "bad thermostat" please? I renewed it shortly after getting it as the gauge was up and down without ever going above 60C but has stayed steady (once warmed up) at 60C since, although i'm sure that's still too cool.
I've also tried fitting large washers (to act as restrictors) in the 'stat outlet and also the heater return to no avail.

[General Confusion]

What about a dodgy temperature sender. If its corroded or furred over it may be giving a false reading.

[Jonny Jeep]

Didn't notice it was an 84 XJ when on tapatalk earlier. It will have two temp sensors won't it? If the one for the gauge is iffy it's not too big a problem as long as the computer knows what temp the engine is from the other sensor. Not sure if the sensors should read the same resistance wise for comparing them. If they are the same type of temp sensor as OBDII XJs then this chart can be used to check them.

[LairdScooby]

Well i thought of a furred up sender but it's not and the general underbonnet heat and heater output is well down on what i would expect.

I've done the old trick of putting a bit of cardboard in front of the grille and that has improved things slightly so i would say it's definitely overcooling.

Do the 'stat housings corrode so the 'stats don't seal properly?

Had that donkeys years ago on a Mk3 Cortina that would never get warm, let alone hot! But i was a very young pup back then and suffered it with no ill effects. These days i'm an old codger by comparison and can't take the cold!

Thanks for that chart - very useful! I'll have to exhume my IR thermometer from wherever i've buried it and compare the resistances to temperature but i think i may have found the problem while typing!
Just searched fleabay for a 'stat housing and found this one :

http://www.ebay.co.uk/itm/THERMOSTAT-HOUSING-JEEP-2-5-4-0-CHEROKEE-GRAND-WRANGLER-COMANCHE-/271965838949?hash=item3f526d5e65:m:m1o807Vpn4iEkkqKGAOlxKQ

Looking at the main picture, the "wall" between the 'stat outlet and the heater bypass is much more definite on the one in the pic than on the one on my engine.

I'm fairly sure Jeep were sensible when using the existing sensors they had when they converted to OBD-II, unlike some companies i could mention! I'll have a think about replacing the 'stat housing while i check out the other options and maybe order one to see if that fixes the problem.

[LairdScooby]

Bit of an update with a couple more symptoms!

Been running round with the grille half covered with cardboard (on the left, mainly covering the area the viscous fan blows/sucks through) and that has seen a small improvement. Now today, i used it for a longer journey with a lot more load. It's probably wise to point out it has an LPG conversion at this point as some of the comments won't make any sense otherwise!

Left home this morning and drove to Bury St Edmunds to hire a car trailer. All normal with the gauge read about 60-70C and lukewarm heater - ran ok.

Picked trailer up and drove 50-55 miles to pick up a car. For some reason the trailer really dragged and long inclines/steep hills would really make it grunt, eventually losing power on gas forcing me to switch back to petrol and then the temperature would rise a bit nearer to 100 at which point i could switch back to gas and it ran fine again, except for the trailer still dragging.

Got to the place where the car was, picked it up and drove off. Really noticed the weight on the back this time but not the dragging feeling with just the trailer. Again on steep hills and long inclines i had to switch back to petrol and then the temperature would go up again for a short while during the rest of the climb. Back on the level the temperature dropped, even while still on petrol.

Got home, unloaded the car from the trailer, got run over by an old granny in a Corsa and now have a sore ar5e (oops - maybe that bit should be on another forum!  ) then took the unladen trailer back to the hire place.
This time it towed totally different, no dragging feeling. As such, the temperature gauge stayed at about 70, ran fine on gas and the Jeep didn't even notice the trailer which is how it should be.

When the temperature gauge did go up, so did the heater output. All this points to a dodgy 'stat and/or 'stat housing/overcooling IMHO so i've ordered a new 'stat housing. When it arrives and i get it fitted, i'll report back.

[Dave69]

sounds like a star stuck open and over cooling, the jeep should tow like the trailer wasnt there.

trailered another jeep with no power issues in my old 94 jeep, towed a cravan and out fragged a corsa so it appears your is a bit down on power while cold

[LairdScooby]

Thanks Dave, you've definitely confirmed my suspicions. I've also posted something similar on the LPG forum to get my suspicions confirmed about the vapouriser icing up due to lack of hot coolant causing the power loss on gas.

A couple of times when it was reading hot i had to hoof it away from a roundabout or junction and it did the business on petrol. Bearing in mind between the weight of the trailer and the car on it, it was a 2T load on the back end! Still gave a good account of itself when i hoofed it like that though.

All the problems i had today point to overcooling. The 'stat housing has the round outlet from the 'stat and a square channel for heater bypass - the "wall" in between these in my 'stat housing has corroded somewhat so my guess is the heater bypass is also acting as a 'stat bypass, hence the overcooling. The LPG vapouriser is tapped into the heater hoses before any heater valves so is independent of the heater but will suffer the same reduced temperature, hence icing internally and shutting the gas down.

In all honesty i just needed confirmation of my suspicons and you've given me that so thanks very much. 

I'll still report back once i've renewed the 'stat housign although i doubt whether i'll be able to recreate the towing experience for some time yet! The car i picked up will yield some useful spares for my 827 coupé (one of the rare ones) such as a front bumper to replace the one that was hit recently. Hopefully be a long time before i need to tow another spares car home for anything!

[Brynjaminjones]

sounds like a stat stuck open and over cooling

This is what I was poorly attempting to say when I said bad thermostat earlier 

[LairdScooby]

sounds like a stat stuck open and over cooling

This is what I was poorly attempting to say when I said bad thermostat earlier 

Ah i see!  It was a new 'stat back in the summer and it hasn't changed a thing. I'm fairly sure it's down to the 'stat housing, just waiting for the new one to land. Will report back once it's fitted and hopefully fixed!

Thanks for all the input and a Merry Xmas to all!

[LairdScooby]

Bit of an update - the new 'stat housing landed day before yesterday and i got it fitted yesterday with a new 'stat as well (92C this time, old one was 88C) and although i have an air lock at the moment it seems to be a lot better. Once i've got rid of the air lock i should know more but the old 'stat was very weak opening under barely any thumb pressure on the top.
Will top the coolant up later today and give it another test run and report back.

EDIT

Rather than do another separate post for the second part of the update, i've just added to this one. Topped up the coolant (rad and tank) and took it for another short run, just round the village really but a total of about 3 miles. Still a slight airlock that seems to be shifting around a bit but the heater output is much better and the temp gauge now sits just under the 100C mark (mostly) as sometimes it still dips for a minute or two. I expect a decent run will sort out the last little bit of airlock and if i feel lively tomorrow i might take it for one.

Got an excuse for that, here is a monthly meet i normally try to go to about 50 miles away on the first saturday of each month which should be a good enough run to sort it out.

[LairdScooby]

Well a week on and it's much better, still not perfect but loads better than it was. Now i've sorted the obvious i think i might look at the vicious (viscous) fan coupling to see if it's sticking a bit.

[Brynjaminjones]

What's the gauge doing now? My new viscous fan clutch on my XJ seems to be 100% all the time, and the gauge never moves from roughly one notch below 100

Sent from my HTC One M8s using Tapatalk

[LairdScooby]

What's the gauge doing now? My new viscous fan clutch on my XJ seems to be 100% all the time, and the gauge never moves from roughly one notch below 100

Sent from my HTC One M8s using Tapatalk

The gauge sits about the same as yours on the open road (about 90C) doing 50-60mph However, below that speed or just trundling round the village or going to my nearest town it floats vaguely up and down between about 70-90C like a very slow windscreen wiper.
When on the open road the heater output is obviously much better too.

I'm going to try a very simple fix shortly before i take it for a spin to have a look at a car i have very little intention of buying - going to see how freely it moves when cold and squirt some WD40 into the gap where it spins. Simple idea/thought being it's gummed up with a mix of dust, oil mist and whatever else might have got in there over the years. Hopefully if it's something as simple as that, i should be laughing.

As usual, i'll post my results (if any) up later.

[General Confusion]

To be honest, those readings don't sound far off. Both of my XJ's (one a '94 and the other a '96) read about that with the slight up and down.

[Mike Pavelin]

They normally run just below 100C

[LairdScooby]

Mine's running between 70-90C after renewing the 'stat (92C) and the 'stat housing. After squirting the viscous coupling with WD40 substitute today, firstly the engine was noticeably quieter (no fan roar!) and the temperature was a little more stable and warm up quicker. I'm thinking i might be better off changing the viscous fan for an electric one.

[eastryjeep]

Simple check for the viscous fan is that it should spin fairly freely with the engine stone cold ie before startup and then be noticably stiffer to turn when the engine is hot (clutch engaged).

Note: this test is ONLY to be conducted with both sets of keys in your pocket, a good pair of gloves on, and at your own risk.

[LairdScooby]

Hmm, spins freely - it turns but there is resistance. it looks like a relatively new viscous unit but it doesn't spin anywhere near as freely as previous viscous fans i've known. I haven't rechecked it since dousing it with WD but i doubt it's any different.

Good point about the keys in pocket but i refuse to exhume the second set from their safe hidey hole just to put them in my pocket! 

If i get time today i might just unbolt the viscous fan and run it like that for a while, just to see. If that is successful i might fit an electric fan instead.

[LairdScooby]

I now have a conclusion for this! The solution had actually been staring me in the face since before i got the Jeep but never mind! Here's a couple of clues :



I also have LPG on in and when i asked the question on an LPG forum, the consensus of opinion was that the vapouriser wasn't icing up, despite the fact it was losing power on gas and eventually cutting out, reverting to petrol.

Firstly, i had definite proof today the vapouriser was icing up :




That was on tickover with 40-50C showing on the temperature gauge!

In short the heater was getting air locked because of the big, high loops in the flow and return hoses and also the fact it was being fed from bottom to top. Given that the sensor for the temperature gauge is rear left top corner of the cylinder head, these air locks probably presented there as well, given the proximity to the heater matrix. In time i'm sure this will clear itself though.

Here's what i did about it :





Looking at the first pic, the lower of the two hoses going through the bulkhead to the heater matrix is actually in the flow/feed hose! This gives rise to another potential air lock scenario! The other two pics follow the hose back so it shows it's connected in the flow from the thermostat.
This next pic shows how the vapouriser is plumbed in parallel with the heater matrix which already has more air locks than you can shake a stick at!

The flow now comes from the 'stat into the top of the vapouriser and out the bottom of it back to the correct flow hose to the heater :



The return hose is now connected to the correct return hose to the water pump, as can be seen in this pic :



A better shot of the join :



and the heater flow and return hoses clipped into the clips Jeep kindly provided for them 20 odd years ago!



I also removed the air intake trunking and the gas feed from the mixer and squirted carb cleaner through both to help make sure the mixer wasn't blocked.

Right, that's the pretty pictures done with, how did it perform? Well the heater now gives hot air consistently from when the temperature gauge is first reading about 40C all the way up to about 80-90C where it spends its time fluctuating slightly now but steady on the open road.

Performance is greatly improved on petrol now and at first was improved to a point on gas, that point being when i hoofed it and it returned to petrol. This was confirmed when i hooked up the lappy.
First things first, i told the Leo it had a 6-cylinder engine, NOT dual coils! This corrected the displayed rpm from 2400rpm to 700-800rpm. Then i stepped through the other basic settings and made sure they were correct.
The default stepper motor position was 74 which was causing a slightly rich mix at idle so i changed this to 63 and got a much smoother tickover. At this point i thought "yeah, all done now, let's give it the beans!" so i did. Within 50 yards it was back on petrol!!!

With this in mind i thought i would check some of the other parameters and found the full throttle position or the stepper motor was 100 - now call me suspicious if you like but to my mind if it's on 63 for idle, it will need a lot more than that for full load! Didn't want to go too stupid so i set it at 200 and gave it a road test.
First surprise was it laid rubber when i planted the loud pedal! Second was the way it rocketed up to 60mph uphill - all the while staying on gas.

I also set up the gas cut-off on overrun down to 1400rpm and also the changeover to gas at 1400rpm on a trailing throttle. This engine speed was the best compromise between getting it low enough to be extra smooth, not cutting out when cold and not having to get the revs so high i'd get done for speeding before it would change to gas!

Meanwhile i had begun to get a bit warm - more than a bit in fact! That heater really cooks now! Even at its hottest before i could happily sit with my paw in front of the vent with it going full chat and i would say it was lukewarm. Now i can just about bear it for 2, maybe 3 seconds before it gets painfully hot!

So several parrots neutralised with one missile! Better than 2 birds with one stone any day!  :lol: Oddly the engine is quieter although that shouldn't be a surprise as i've always maintained that when an engine is properly on tune it will be at its "happiest" which is generally the quietest and most efficient. The perfromance is certainly improved on both petrol and gas, the gas is partly down to setting the LPG up better and the petrol i think is down to more consistent temperatures and lack of air locks within the cooling system which would alter what the PCM sees as the engine temperature and would alter the tuning accordlingly.

All in all a good afternoons tinkering and thanks for all the input from everybody!
I've saved a copy of the LPG config file just in case, hopefully i won't need it but at least it's there! Hard to believe so many problems could come from one person - whoever installed the LPG in the first place!

[daggie]

 
glad you've sorted it

[LairdScooby]

Thanks! Me too!