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No heat unless I raise the RPMs
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golfboy7
Novice
Nov 8, 2007, 5:06 PM
Post #1 of 13
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No heat unless I raise the RPMs
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HI all,
I own a 2000 Jag Stype 3.0 liter and have a heating issue.
I noticed this happening a couple weeks ago and it is very consistent now. I'll use an example to illustrate what is occurring:
I'm driving down the highway, doing 65, RPMs are around 2200 or so, and I get off the highway and come to a stop at the light at the end of the off ramp. After idling at about 800rpms, the hot air which was blowing hot on the highway, starts to gradually get back to the outside tempurature. Then when I start driving again, and the RPMS go up, it starts blowing hotter again.
If i'm coasting and the rpms are at about 1500, it will not blow hot...the 'limit' here is at about 2k (or so) RPMs.
Please note, the RPMs do not affect how much air blows, only the temperature.
Any thoughts?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 9, 2007, 2:33 AM
Post #2 of 13
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Re: No heat unless I raise the RPMs
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This sort of points to air in the coolant either because it is low or overheating possibly from fan(s) not working at lower speed when needed most and bubbles from boiling won't transfer heat well at all odd as that sounds.
I think this uses the recovery tank and pressure cap on it with just a small hose to radiator - right? This makes it hard to know that the radiator is really full of just coolant. If that design you can squeeze a radiator hose and detect just coolant swishing to the recovery tank and back with the cap off of the tank.
You really need to verify the coolant level and that fans are working when they should if only to rule that out. Temp gauge should stay steady once warmed up and not fluctuate much at all - ever. Could be some other problem with controls but do rule out this coolant problem. If that's the issue, run - don't walk to take care of the source problem before it can cause further problems or damage,
T
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golfboy7
Novice
Nov 9, 2007, 6:51 AM
Post #3 of 13
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Re: No heat unless I raise the RPMs
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Thanks for the reply Tom.
I'm very uneducated about heating and cooling systems...how can I verify that the fans are working at lower RPMS? I guess I just don't know what I'm looking for when I open up the hood.
Thanks for the help again.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 9, 2007, 8:05 AM
Post #4 of 13
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Re: No heat unless I raise the RPMs
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Ok: Sorry if I confused you which I can do sometimes. This is important so get help. Have a real mechanic verify the coolant level and observe this. That may not be the problem but you need to know,
T
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golfboy7
Novice
Nov 9, 2007, 8:20 AM
Post #5 of 13
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Re: No heat unless I raise the RPMs
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This is getting a little off topic here but I like to speak my mind...
Don't they check the other fluid levels when they change your oil? I could have sworn that was pretty much included in any kind of oil change nowadays.
For some reason, I have this underlying 'feeling' whenever I take my car to a place to get it fixed, that they cut as many corners as possible in order to cut costs while still charging me for the services they 'say' they performed. And I think the reason I have this feeling is because I know most people don't know squat about their cars (me included). The car repair shops know this, and know they can take advantage of this with very little reprocussions (spelling?).
Anyway, I will have this checked this weekend but I doubt I will be allowed to watch them do it.
Thanks again for the info.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 9, 2007, 9:08 AM
Post #6 of 13
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Re: No heat unless I raise the RPMs
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THAT'S A PERFECTLY GOOD TOPIC! I do all my own oil changing service. The craze today is for speedy service and they claim they check all this stuff and can get a lot done but something's missing with most of these places.......
Even dealers will bait you with reasonable prices sometimes. In general, places are advertizing the whole service for about half of what it costs me to do it labor free! They buy drums of product and I can't compete with that. Most cars you can check fluid levels by just looking at the translucent reservoir. If this has the pressure on the recovery tank it may show full but doesn't say if the radiator is and these quick places can't afford trained techs for this service. What's worse is if it needs fluid added to something that is a warning that something is wrong!!!!! and you don't get warned!!!! If I find brake fluid, trans fluid, coolant, gear oil, PS fluid or tire pressure way too low on one tire I would tell you that, that isn't right and the places just can't do that.
This is not to blame anyone because the customers rule with this and want fast service for routine things. When things are within norms this works well. It's when something is wrong that you don't always get the warning. You are going to have to have some things checked exactly at your request and this is one of those times,
T
Ps: Bet you don't know how much pressure is in your spare tire right now - do you? I do on my own and customers!
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golfboy7
Novice
Nov 9, 2007, 1:15 PM
Post #7 of 13
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Re: No heat unless I raise the RPMs
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Ok, a friend and I just went out and looked at the fluid level.
The coolant level container, where you would pour more coolant in if you needed too actually sits higher than the radiator, and there is a level indicator on the outside of the foggy plastic which says (MIN ----- MAX) and these lines are about a half an inch apart. (Which, judging by the size of the container would only amount to a few ounces between the min and the max levels).
The tube coming out from this container that goes to the radiator is a hard tube and squeezing it is impossible. My friend did squeeze the rubber tube that comes out of the other side of the radiator and we could hear some noise, sounded like fluid, coming from a few feet back. (sounded like it was coming from underneath, and between the engine and the cabin).
I have to drive my car to my friends house after work today, it's about a 10 minute drive at about 35 MPH avg. My friend told me when I get there to leave the hood down and the car running, put it in park and listen for the fan to start up to see if everything is working ok.
Neither of us really understands how this would affect the level of heat blowing from the engine. Can you explain how this works? Keep in mind it blows hot at about 2500+ rpms, warm at around 2200 and cool to cold at anything under 2000.
I wish I understood more. <----on that note, are there any good websites, maybe one that has diagrams, where I can kinda study my Jag and learn about how the different components in cars work?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Nov 9, 2007, 2:41 PM
Post #8 of 13
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Re: No heat unless I raise the RPMs
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Ok: That container as you put it is an overflow reservoir and probably has a screw cap - not just a pop up cap like most washer fluid containers would have. The small tube from that to radiator would not be the place to squeeze and you would at a radiator hose which I think your friend did. That should push just coolant back and forth to the reservior. Any air should bubble out and only coolant can return so it's self purging and if the whole system was in proper shape would get out the last bit of air after a while if it was drained like for other work or changing the anti-freeze.
From cold the larger hoses - should be one that goes high on radiator and one lower is return back to engine should demostrate that there is no pressure in them when just sitting cold and when engine warms, coolant expands some and would be maintained at about 15lbs in the system which raises the boiling point of the coolant the same way a pressure cooker does for cooking if you are familiar with those.
If it can't build up pressure then there is a problem. That could be as simple as the cap itself or a leak somewhere. Without building up pressure enough the coolant might not purge to the reservoir or be able to draw back just liquid when it cools and contracts. That's how that deal works.
Physics 101: Water boils at 212F. With 15 psi of pressure the same water won't boil till 257F. Most engines operate at close to the unpressurized boiling point so being able to stay liquid is critical. Anti-freeze mixture does add just a couple degrees to the boiling point but it's insignificant by itself.
There will be some hot spots inside your engine and a costant flow of liquid is needed to cool the engine to a uniform temp. It a spot even boils you have added air as bubbles that are moving around and don't exchange heat well. Even 150F water will burn your hand but you can wave your hand in an oven that was just at 350F and if quick it wouldn't burn you - get the idea. Your heater core is just a mini radiator like the one for the engine and if just bubbles or plain air passes thru it it won't feel warm at all. If the electric fan(s) are not coming on the coolant could be boiling but less apt to when driving at some speed like about 40mph most vehicles barely need the fan. The speed of the car is then the speed of the air going over the radiator. Two things happen when driving along at some speed - 1. The load on the engine increases making heat faster but the air speed (#2) can cover that and all is well and your heater works. When you slow down, the water pump is pumping slower and for a while the engine needs cooling more than it did moving along. Fan takes care of that.
That's with everything normal. If the slow down causes boiling or even a mix of liquid and air the heater would suffer. Worse is that is an engine killer as there could be spots much hotter than even your temp gauge reads which is why you hear about engines "blowing a gasket" type thing.
You heard so remote sounds when sqeezing that larger hose and usually you will not hear just liquid but would hear air if it was in there. That would explain what is happening in this case in just that scenario. It could be some other thing completely but I just wanted this part ruled out first.
These are common priciples and not just your car. Your owner's manual should discuss quite a bit about fluids and levels but is not intended to be a repair manual. It will tell you where the common check points are for this vehicle and what type of product should be used as needed.
Many plain cheap repair manuals for your car will cover basics of operation. If you want to learn more about the principles of the many functions you should buy an auto mechanic's textbook. They probably are available on the web and lots will be free. Specific repair instructions are available here and there on the web. If you want a complete book on your car try AllDataDIY.com and you would download the whole shooting match for your car. Some techs here have the pro editions and do share exact diagrams and info on specific parts, locations etc. It's expensive and I don't happen to have that.
The principles should be understood before you need specific instructions for just one model. There used to be a good book called "auto mechanics for idiots" or something like that that was pretty good.
For now I was just looking to rule out air/bubbles in the system and then it would go on from there as to what to do next,
T
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golfboy7
Novice
Nov 9, 2007, 3:31 PM
Post #9 of 13
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Re: No heat unless I raise the RPMs
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Tom,
This information is incredible.
I'm 27 years old and this is the first car I have 'purchased' as my own. I plan on learning the principals as you suggest because I want this car to be a restoration project car down the road. IE I do not plan on selling it when I get a new car, but rather I plan to work on it to keep it in good condition.
Anyway. Thank you so much for all your help, it seems as though this is a little over my head at the moment so I will have this looked at over the weekend and will post an update sometime soon.
JR
PS I have bookmarked these forums as they are some of the BEST, most active forums and users I have ever found.
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golfboy7
Novice
Nov 12, 2007, 4:20 PM
Post #10 of 13
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Re: No heat unless I raise the RPMs
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***after weekend UPDATE***
I was unable to get my car in to the shop to have this problem looked at. However I do hav a little more information that may help (or may not...I'm not sure).
I had to run 1 errand on Saturday afternoon, it was about 8 miles away by highway and I did about 65-70 on the highway. The air was blowing hot while I was moving at these speeds, however when I got off the highway I got stuck at a railroad crossing for a number of minutes where the RPMs dropped and the air tempurature quickly followed.
So I did a test. I put it in neutral, and rev'd the engine (it's regulated in Neutral to about 3000 RPMs) and kept it at the rev limit while I was stuck here. As I did this I tested the air temp and it got hot again.
Does this new information change anything?
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way2old
Veteran
/ Moderator
Nov 12, 2007, 5:56 PM
Post #11 of 13
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Re: No heat unless I raise the RPMs
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You may have a water pump that is not flowing enough coolant at lower rpm's. If the impellers on the water pump are worn down, it will do what you are describing. Not saying that is what it is, just suggesting another part to check.
Post what systems you are interested in and I will see what I can do for ya. Just do one at a time so my old brain does not get too overwhelmed.
Being way2old is why I need help from younger minds
(This post was edited by way2old on Nov 12, 2007, 6:04 PM)
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mcmurer
New User
Nov 28, 2007, 11:40 AM
Post #12 of 13
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Re: No heat unless I raise the RPMs
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i had a similar problem on my mercury sable. the problem progressively got worse. when i finally removed the waterpump i found the impeller fins were completely worn down. at first, 1500rpms was enough to keep the coolant moving. it gradually increase to over 3000 rpms. new waterpump fixed the problem.
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golfboy7
Novice
Feb 4, 2008, 7:56 AM
Post #13 of 13
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Re: No heat unless I raise the RPMs
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***UPDATE***
Problem fixed!!
Local repair shop looked at system and found the resevoir had cracks in it! Very tiny cracks in plastic made for low system pressure. Replacing the resevoir fixed the problem. Now I have another issue.
It's on the front page.
Take a look.
Thanks.
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