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Can bad condenser fans cause overheating?

22K views 117 replies 12 participants last post by  Lockettc 
#1 ·
Hi guys and gals - my 95 LWB has had an overheating problem since I bought it a few months ago. I know that the condenser fans don't work - and I have a replacement set but haven't fitted them yet.

I can't run the aircon without overheating, but all other times its fine. The main symptom I've experienced when overheating is a highly pressurized coolant system. It blew the expansion tank cap once from it. I replaced it and now drive without aircon.

I know the pressurization symptom can be a slipped liner. Any ideas?
 
#41 ·
PS if it is crook valves (i.e. compression doesn't come up with a squirt of oil) then you have to take the heads off to give them a grind, and when you do that you can inspect the valve liners and replace the head gasket and maybe get the heads machined which will put your mind at rest even if it doesn't run any better.

Is it burning much oil?
 
#42 ·
Hey Johnno thanks

Yep tested properly I think. Warmed engine, pulled all plugs, throttle wide open across 10 revs per cylinder.

I'll try adding a squirt tonight. Should I try all 8 cylinders? She's not eating oil that I know of. Then again, it's just been changed.
 
#43 ·
Your cams change the valve timing on the intake and exhaust strokes, and shouldn't affect the compression stroke. (See the nice animated gif on wikipedia: http://en.wikipedia.org/wiki/Engine )

Low compression across the board usually just means loose fitting piston rings. This is a symptom of an older engine, and 125 sounds about right to me for a 20-year old rover. Basically the gap between the piston rings and cylinders is big enough that a little bit of air is able to pass through into the crankcase. This makes the engine less efficient and less powerful. Adding a squirt of oil before the test helps to seal the piston rings and raises the compression numbers.

You can replace the rings and make the engine as good as new, but it is not a trivial job. Besides, like johnno says, if the engine runs, it's not really an issue. it just means you're getting something less than the advertised 200hp.

The worn piston rings could conceivably explain why your crankcase & gas tank are getting pressurized, assuming the EVAP control system is gummed up somewhere. Have your checked the PCV hoses to see if it's working properly? The extra air in the crankcase should get vented into the intake. There are some hoses connecting a filter on the passenger-side valve cover to the air intake next to the throttle unit. If these aren't working properly, then the air could get forced into your gas tank via the charcoal canister. This would be pretty unusual, since I think there's a valve next to the canister that's supposed to prevent that.

Anyhow, this still wouldn't explain why your coolant is getting pressurized... Did you open your coolant reservoir cap during the test? If your coolant system was pressurized during the test it could throw the readings off.
 
#62 ·
This is interesting Scott. I just read this about PCVs: http://www.britishv8.org/Articles/Positive-Crankcase-Ventilation-PCV.htm

I want to check my PCV & EVAP system. Pressure is coming from somewhere I think. I'm going to do the coolant, but it seems as though I can't drive a mile now without overheating. (I'm on stop #4 right now for her to cool down!). It is a warmer day here though, but still this is ridiculous.

Is there any way that crankcase pressure could make it's way into the coolant system?
 
#44 ·
You give it a squirt of oil, say a teaspoon - if the compression comes up then its worn rings, if it doesn't change it is worn valves. Personally I would say it is both and the oil might bring it up a bit but not all the way - i.e. the motor is a bit tired. I would probably do all cylinders if I was going to the trouble.

If the rings are so badly worn that you are getting blow past, pull off the oil cap while the motor is running and see how much fumes are coming out of the crankcase. You'd expect to see something on a worn motor.
 
#45 ·
I'll address the previous two replies when I'm not typing on my iphone ;-)

Little update: my TPS was indeed bad. Swapped a used known working unit and all my hesitation problems went away, from cold too, which is when it was the worst.

Didn't have a chance yet to drop some oil into the plug holes. And I might not bother if the only things it could mean are bad rings or bad valves. Needs a top end job it sounds like, and I'm not sure I want to bother with that just yet if it's running.

My remaining issue is intermittent overheating. Could bad rings and/or valves lead to overheating?
 
#46 ·
Probably not - it only overheats when you use the air con and otherwise it is sitting in the middle of the temperature gauge?

Have you checked that the air con fans are cutting in? You say they run continuously - that sounds like a short as they should be temperature dependent - they should also keep running when the motor is turned off for a while. Is the a/c compressor clutch cutting in and out? If it's running continuously it could load up the motor.

I would have thought that with a slipped liner/head gasket problem the cooling system would pressurise even if it was cold - I think the pressure you are describing is just from heating up. One thing's for sure, if you keep boiling it you will end up with a slipped liner, so keep an eye on it and think about how much you need the aircon.

I would go back around the basics:
Check hoses for blockages, crimps etc
Flush the radiator
Check the coolant level
check the fan/s operation
Check the thermostat
Check the fan belt
Check the water pump
Clean out the radiator fins
Dragging brakes
crook temperature gauge
Timing incorrect
 
#47 ·
Probably not - it only overheats when you use the air con and otherwise it is sitting in the middle of the temperature gauge?
No - I'm not using the aircon at all. It seems to be overheating after the engine warms up and if I push it a little. Otherwise, it seems like if I drive gingerly it's fine.

Have you checked that the air con fans are cutting in? You say they run continuously - that sounds like a short as they should be temperature dependent - they should also keep running when the motor is turned off for a while. Is the a/c compressor clutch cutting in and out? If it's running continuously it could load up the motor.
I will double-check this, it's been awhile since I've been looking at the fans, but from memory, the twin condenser fans run continuously, and the VC fan does seem to kick in with temp, but then it never seems to have the resistance that others have explained to me, whether hot or cold engine.

I would have thought that with a slipped liner/head gasket problem the cooling system would pressurise even if it was cold - I think the pressure you are describing is just from heating up.
Yes, that's pretty close to what it seems like.

One thing's for sure, if you keep boiling it you will end up with a slipped liner, so keep an eye on it and think about how much you need the aircon.
Good to know. I think I might just start on the front brakes (which I need to do anyway) since I have the parts. I've just finished the rears. After all are done that should tick off the dragging brakes possibility. But I don't think this is it – you'd think I'd have some smoke or something if that were the case. I don't want to damage an engine that's already tired, so I'll take my time with this diagnosis before driving much.

After I blew the upper rad hose I replaced it with a new one. When doing the TPS last night I noticed a few hoses that look really tired and are definitely due for replacement. I might just have a look at some hose sets for the coolant system...

I would go back around the basics:
Check hoses for blockages, crimps etc
Flush the radiator
Check the coolant level
check the fan/s operation
Check the thermostat
Check the fan belt
Check the water pump
Clean out the radiator fins
Dragging brakes
crook temperature gauge
Timing incorrect
- hose blockages & crimps: yes, worth checking. I'll add those to my list.
- coolant level: lost a bit when I replaced the thermostat recently, will double check & re-bleed.
- fan/s operation: will double check to confirm what's happening
- thermostat: just replaced with a new one a few days ago. Still overheating.
- fan belt: how do I check this?
- water pump: been on my list to look at. How do I check this?
- radiator: had compression check & flush and they told me it looked brand new, about 50 miles ago
- dragging brakes: maybe. Will remedy either way soon enough
- crook temp gauge: really?
- timing: yep. Will grab a timing gun. It's about time. (See what I did there?)

Thanks so much for all your help john & everyone. It's very much appreciated.
 
#48 ·
Well its all a bit hard to say - if you pull the heads off you can see really quickly if you have slipped a liner and its not a huge deal to actually do it, and then you can cross it off the list. If the liners are OK, you can get the heads machined, valves done and replace the gaskets which crosses another item off your list. Yours is a 4.2 and as I understand it, slipped liners started to be a problem with the larger motors and it's a fairly common problem.

It might be that the initial radiator problem led to overheating which led to a slipped liner.
 
#50 ·
Yes I've heard slipped liners can be a pretty common issue with these after overheating. Since I've owned the truck, I've only really had one severe incident of overheating, but several more where I've turned it off right when the temp gauge started climbing. It's certainly possible and even probable that overheating has caused at least some of my symptoms.

I guess I don't really have an idea as to how much work this is, and whether or not I'm capable of it, hence my hesitation. I'd love nothing more than to pull the heads and get some new rings, gaskets, valves etc in there, and learn along the way. But with me having a couple hours a day maximum, and no experience ever pulling apart an engine, I'm not sure it would be wise for me to go there. But I'm really on the fence about it.
 
#49 ·
if your viscous fan is working you will definitely hear it when it engages. If you don't hear a roar when it gets hot, I would replace the fan or fit thermos. You really can't check the water pump without removing it. The impeller blades that pump the water can rust away if someone has not used coolant all the time in the past. Also the timing cover that forms the rear of the water pump internal can become corroded which affects water circulation.
 
#51 ·
I definitely DO hear the VC fan when it engages. The only inconsistency with my VC is that several people have mentioned how to 'test' whether it's working by feeling for resistance (the details escape me right now), and I've never been able to identify that resistance. But the fan definitely kicks in when temp comes up. Sounds like a little freight train under the bonnet, and I kinda like it ;-)

Should be working though – it has a brand new clutch. Also, I just installed a new thermostat a couple days ago (no change). I've never checked the water pump. Not sure what to do there, but it might be time to look deeper into that.
 
#52 ·
Apparently I can get a complete set of all gaskets, rings, bolts, lifters & valves for under $1k. That's news to me.

All the nonsense that follows, of course, is assuming I've completely inspected my overheating problem and determined it to be engine internals.

Okay - here's a set of stupid questions:

- do you have to pull the motor out of the truck for a complete head job like this?
- in your opinion, is this a reasonable task for a home mechanic such as myself to take on at home?
- how long is a piece of string?
 
#53 ·
You remove the plenum chamber, exhaust manifold and other bits and pieces, remove the rocker covers and remove the heads. It's as easy as especially with a pushrod motor. Just follow the book. If you don't need to drive the car I would pull the heads off before I buy any parts, because if you have a slipped liner you will need to remove the motor and take it somewhere to get it fixed, and once you do that you would go for a full rebuild and they will do the valves etc. If the liners look fine, you would probably take the heads somewhere for a rebuild else you can do it yourself but I wouldn't, a shop will do it quickly and you don't need the experience. If there is a crack in the head, you can get it welded and machined.

Personally it sounds like you have checked everything else regarding the overheating problem, pulling off the heads is not a big job, and if it all looks fine and you think its not worth doing up the heads when the bore is probably stuffed as well, then put it back together with a new head gasket, inlet gaskets and exhaust gaskets. I would have thought $1-200 in parts.

What you say about the cooling system pressurising when cold supports a slipped liner, cracked head or blown head gasket so have a look and if its ok then cross it off the list.
 
#54 ·
Little update. No discernable play in water pump bearing from the outside. Unit looks very clean, no discernible leakage either.

The large lower radiator hose T-junction almost appears as if it was installed backwards, causing the larger hose that comes from under the expansion tank and going to the T-junction 'top' to be a little kinked (since the top 'T' appears to be angled to the wrong direction). A big zip-tie is holding it 'open' now. Will go for a run tomorrow and see if I can get it to start to overheat again I guess. It's the little things isn't it?
 
#56 ·
Hmm. string? keep pulling and see if you find the end.

The head gaskets & valves are all done with the motor in. The piston rings are done with the motor out.

The head gasket is not too hard, especially if you're already doing your own brakes. You would probably hire someone to machine valves (if you needed to do such a thing). The piston rings you could probably do, but it's a really, really big job.. maybe save this one for a rainy day.. or a rainy month.


As for your overheating:

- if you have a head gasket / slipped liner, then this could explain the overheating, especially if air i.e. being forced into the coolant system.However, since your compression results are all within 10%, then this probably isn't your problem.

- Overall low compression due to rings, etc, would not explain overheating.

- Did you do the compression test with the coolant cap off? If the coolant tank is getting pressurized, this could affect the readings.

- Assuming the head gasket / liner are fine, if your coolant is getting hot enough that it's boiling, then there's probably something wrong with the fan/radiator/coolant/pump. Realistically it should never be able to get that hot, regardless of how aggressively you drive.

- Does it overheat at highway speed or city driving or both? On the highway you will be getting a lot of airflow on the radiator, so the fan doesn't matter as much.

- When you squeeze the upper rad hose, does it feel like it has liquid or air in it?
 
#59 ·
Hi Scott, no I didn't take any coolant caps off before testing the compression. I know my fan(s), radiator and coolant are all good. Water pump is the unknown. It only overheats when I'm pushing the engine, so higher speeds, yes. I've squeezed the upper rad hose several times after a decent run and it has NEVER felt like there's been any coolant in there. Always feels like it's filled with hot air.
 
#63 ·
No there should ne no interconnection between the crank case and the coolant system unless you have a failure, cracked head, cracked block, slipped liner, head gasket...If you are pressuring the coolant system with anything other than the vapor pressute of the coolant, then you have a mechanical failure.
 
#65 ·
Update and a half!

I started topping up & bleeding my coolant. Radiator and expansion tank were VERY low. After giving it an entire large bottle, I started suspecting something. Halfway through the second large bottle I glanced under the car, where I found the other half of my coolant. Truck was running.

It seemed to be coming from the back end of the engine somewhere. It was dripping off what I think is the tranny bell housing, right next to the cats.

Makes me wonder if I pinched the thermostat when I replaced it.
 
#66 ·
My overheating issue has existed since I got the truck, but it's definitely been worse in the last few days than ever before, which is what makes me suspect a leak at the thermostat seam, because I just replaced it and I remember it being a bugger to keep the thermostat in-place while re-attaching the cover. I suspect that's where my coolant leak is coming from, because it never used to leak coolant like this.

But apart from that, the fact that my VC fan never feels 'stiff' after a drive makes me suspect the water pump. I don't think the bearing is bad because the shaft feels solid, but whatever it is that engages the pump I think has gone.

I also just learned that hoses, if old, can collapse from the vacuum. Interesting. Sounds like I should re-fit the thermostat with a new seal, then replace the water pump with a new coolant hose kit.
 
#69 ·
But apart from that, the fact that my VC fan never feels 'stiff' after a drive makes me suspect the water pump. I don't think the bearing is bad because the shaft feels solid, but whatever it is that engages the pump I think has gone.

I also just learned that hoses, if old, can collapse from the vacuum. Interesting. Sounds like I should re-fit the thermostat with a new seal, then replace the water pump with a new coolant hose kit.
the water pump is connected directly to the fan shaft. It does not get driven by the VC. the VC is there to allow the water pump to turnat belt speed while the fan blades spin slower. You could totally remove the fan blade and the VC and have no effect on the water pump. if the VC does not get stiff it simply allows the fan to rotate slower than ideal and therefore doesn't draw as much air through the radiator.

old hoses can colapse, however if I recall correctly, you are encountering a pressurized coolant system which woud expand the hoses not collapse them.
 
#67 ·
A few old tricks: tie thread to thermostat and run thread up through the housing to hold it in place while mounting the housing or just a dab of super glue to hold thermostat in place. No more fussin' with it.
 
#72 ·
Little update. I removed my water pump and the thing literally looks brand new inside & out. Rotation is smooth and free of play. Propeller looks brand new. Heck even the seal looks new.

Saw coolant in both ends on crankcase side, so I can't find any reason it wouldn't be working. I'm starting to think perhaps a combination of low coolant and old hoses may be my culprit. Maybe an air lock. Maybe, somehow PCV system somewhere?

I remember being told the wrong belt was on there during my recent full inspection. Though my belt looks almost new, I think I'll replace it anyway just to be sure. Pulleys all look good to me, but don't know what I'm looking for.

When trying to undo water pump pulley bolts, belt was sliding on pulley.
 
#73 ·
Stick with the basics first - if you have low coolant, that is the most likely culprit. Fix up the leaks and then see if it is still overheating. You might have fixed the original problem and started a new problem while carrying out repairs - its a well known and documented fact (I read it on the internet) that the average handyman trip requires three trips to the hardware store -I reckon the same principle applies to home mechanical repairs.
 
#78 ·
Yeah it's really sounding that way, isn't it. If you have a couple weak spots, the effect could be cumulative, and once the temperature gets away on you, you can develop even more problems, as I guess you've experienced.

If you're looking for performance gains, you could start by installing a couple aftermarket water / oil temperature gauges. They're pretty inexpensive, and you might find them more accurate than the built in land rover one. More of a performance car thing than a rover thing. Maybe you should be on the TVR forums, where they're installing Garrett turbos and what not. ;) Though the easier way to make her faster would be to kill some weight... I always wondered why nobody makes an aftermarket carbon-fibre hood for the RRC. :D
 
#79 ·
Yeah. I've heard nightmare stories about the heater core job. Not looking forward to that but neither my heater nor A/C work properly, so I know I'm going to have to go there one day.

I've thought about getting some aftermarket gauges in. Just another thing to get my head around, but more accurate info is very welcome.

When I lived in England, my brother in law had a buddy who had a TVR. No idea which model - I don't know anything about them, but it was a crazy go kart. I'm not at all interested in getting more performance out of my engine. The 4.2 does the job perfectly well for me. I'm mainly interested in handling and reliability... and I bought the car because I knew it was high-maintenance, I liked how it looked and it was nice to have a piece of England back in The States.

I still love the truck to pieces and will do everything within my power to keep her going as long as I can. Crazy RoverBug.

I don't know much about composite fabrication like CF, but I know there are a lot of guys who make their own parts in their garage. In fact, that'd probably be the only way I'd be interested in something that would cause performance gains - making the truck lighter. I don't want to change all the drivetrain / tranny / etc just to get another 50hp like some other guys are willing to do. In fact, my favorite part of the truck is the transmission... I get picky about them and this thing is smooth as butter and always seems to shift at the right time (which is more than I can say for my wife's 2013 Subaru Forester Turbo 5spd autobox - can't stand that tranny.)


Anyhow, update on the truck: I'm pulling each coolant hose and cleaning them out and inspecting them, one by one. Pulled and am cleaning out my expansion tank. I've ordered a new thermostat gasket, new serpentine belt, new coolant and new battery (unrelated). I'll fit those as soon as they get here and re-bleed the coolant, and put new coolant in.

To recap:
- pulled water pump for inspection, looks brand new, all in good working order
- inspecting & cleaning all coolant hoses now
- pulled expansion tank for cleaning
- re-installing (new) thermostat with new gasket
- REALLY looking forward to getting her buttoned up and her running like a dream (fingers crossed).
 
#80 ·
Don't forget to have a look at the heater hoses when chasing leaks - especially where they join onto the bit of metal pipe that has the filler tower on it as the metal corrodes under the hose - and check the hoses for pinholes, especially if you get any missing, leaking hoses always seem to aim at the distributor. Don't remove the hoses from the firewall unless you have a very good reason - they are a mongrel to replace.

When you put the thermostat in, you can see there is a side with an actuator - that goes on the hot side i.e. towards the motor. You can check the thermostat by chucking it in boiling water - it should be closed when cold and open when hot, and it should open all the way when hot - in fact at 88 degrees C - don't know what that is in fahrenwhatsits.
 
#81 ·
Lol it's ok John, I am fluent in The Queen's English ;-)

I don't think my 4.2 has the filler tower I've seen on the other motors. How do I check for pinhole leaks?

Good tip about firewall hoses - they were next one list for cleaning.

I'm waiting for a new belt & t-stat gasket to arrive. I will do the string trick so it goes in properly and in the correct orientation. Really looking forward to getting her buttoned up.
 
#82 ·
Well I'm guessing you have a leak somewhere as you said you had low fluid and it had to go somewhere, and low fluid will definitely lead to overheating. If it is leaking from the thermostat housing, there should be a puddle of green (or whatever colour dye you have in the coolant) water sitting under the distributor. If you get the motor up to operating temperature so it is pressurised, pin hole leaks should be evident as a little stream of water or maybe drips etc. Make sure you top it all up and bleed off the air. If you want to heat it up a bit, blank off a good chunk of the radiator with a sheet of newspaper.
 
#83 ·
Thanks John. I'll get it all buttoned up and run it a little hot and have a look for leaks. When I brought my truck into the radiator shop I had them do an inspection of the hoses in addition to pressure testing the system. At the time, they said the hoses were fine apart from a pinhole leak in the upper rad hose, which I replaced.

But nothing like having a look as someone who cares ;-)

One thing to note. That hose I mentioned earlier that looked kinked - when I removed the expansion tank to inspect I clean it, I fiddled with hose routing to get it back on. Not only did it seem like it was routed incorrectly, but I suspect the hose is not the right part, because the length that was almost kinked was simply too long. The slack was causing it to kink. So I cut an inch off at a time until it looked right, ended up hacking about 4" off it! It now sits nicely 'open'.

There was some white corrosion at the end of that hose that connects near the water pump, and also the cast fitting that holds the thermostat in had some corrosion as well, which I cleaned. And there did seem to be a tiny bit of oil in the expansion tank, which I cleaned out. Not good, but I'm just gonna run it and hope for the best.

If I kill the motor I might just order a new one from Cannibal or AB.
 
#84 ·
Update : got it all buttoned up with new thermostat installed correctly. Refilled with new coolant and did my best to bleed it.

Just took her for a spirited drive and she never went over the halfway mark on temp. In fact, she runs a tiny hair lower on the gauge than she did before, but still up to operating temp just fine.

That's a win in my book. Couldn't have done it without you guys. Thanks.
 
#85 ·
Hope you got there - keep an eye on the coolant level for the next couple of hundred k's. PS there should be a level sensor on the coolant tank that gives you a warning light if the level drops, your's mightn't be working.
 
#86 ·
I hope so too John. I've never seen the light on, and I know I've had cases when it should have been, so it mustn't be working.

I'll keep checking the level over the next few months probably - unless I get to drive her more than a couple miles a week anyway ;-)

Still have the hesitation issue a little bit. I thought replacing the TPS had solved it, but it seemed to only fix it 'halfway'. Seems to go away almost entirely when truck is warm. I'm thinking either fuel or maybe the used TPS wasn't 'new' enough.
 
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