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Overheating after a bunch of engine upgrades

X

XJVenom

NAXJA Forum User
Location
SLC, Utah
About a month ago I replaced my t-stat with an OEM 195 and at the same time I replaced my OEM radiator with a CFS 3-core. The engine ran perfect - around 180, and it would RARELY go above that in city driving according to the temp gauge. Now I just finished installing some major upgrades just a few days ago (Leach header, 99 intake, port/polished HO head, increased CR to about 9.0, 2.5" high-flow cat and muffler) and now my gauge constantly stays at 210. Also, now on the highway it fluctuates between 190-210. I already had a high-flow cone air filter, bored TB, and Jacob's Off-Road Ignition kit upgrades before I made these upgrades. The weather here has only been maybe 10-15 degrees warmer than a month ago when I first installed the new rad and t-stat. (its been about 75 degrees lately)
What could be causing such an increase in engine temperature? I was much more reassuring to see the gauge constantly at 180 previously compared to the 210 now.

Venom
 
Have you changed the injectors?

Between a low restriction intake, headers and a larger exhaust, you're flowing a lot more air. Your injectors may now be undersized, which could result in a lean-run condition. Engines that run lean also run hot.

Is there a shop nearby where you can hook it up to an analyzer and get a reading on the exhaust?
 
My 98 Stays rock steady at 210 no matter what I'm doing, thermostat is/should be a 195F tstat. Did you burp the system ???
 
Eagle said:
Have you changed the injectors?

Between a low restriction intake, headers and a larger exhaust, you're flowing a lot more air. Your injectors may now be undersized, which could result in a lean-run condition. Engines that run lean also run hot.

Is there a shop nearby where you can hook it up to an analyzer and get a reading on the exhaust?
Click to expand...

That's exactly what I was thinking. The engine's almost certainly running lean and if you find that the deposits on your plugs are whitish, that'll confirm it. You'll need a set of Ford 24lb injectors to correct the leanness.
In the event that the engine runs a little rich after installing these injectors (like mine did), you can install a MAP adjuster (it's easy to make one) to adjust the A/F ratio back to stoichiometric.
 
I've already made a MAP adjuster because I was also afraid that it might be running lean. I set the votage to 5.8, but that didn't seem to make any difference. Then again, I thought the MAP adjuster only really affects the fuel ratio in WOT.

Would cranking up the MAP adjuster and keeping my original injectors work just as well as installing 24lb injectors with no MAP adjuster instead?

How much would I be expecting to spend to take it to a shop for A/F ratio testing?
 
RichP said:
My 98 Stays rock steady at 210 no matter what I'm doing, thermostat is/should be a 195F tstat. Did you burp the system ???
Click to expand...

Yes, I did burp the system.
The system also sucked out a bit of coolant from the reservoir so It's probably burped the remaining air on it's own as well.

Any other suggestions?
 
Just for laughs try another factory thermostat, it really should not fluctuate on the hiway at all but should remain rock steady at speed. How old is the fan clutch ??? The other question is how did you check your serp belt tension when you put it all back together. Most peoples 'feel' for the correct tension of 160lbs on a used belt is closer to 80lbs when actually checked with a krikit tension gauge..
 
XJVenom said:
I've already made a MAP adjuster because I was also afraid that it might be running lean. I set the voltage to 5.8, but that didn't seem to make any difference. Then again, I thought the MAP adjuster only really affects the fuel ratio in WOT.

Would cranking up the MAP adjuster and keeping my original injectors work just as well as installing 24lb injectors with no MAP adjuster instead?
Click to expand...

No. Your stock injectors are already at the limit even without the MAP adjuster and with it, you're only trying to flog them even more.
It's better to get bigger injectors and, if necessary, try to lean them down rather than flogging smaller injectors.
I have Ford 24lb injectors on my 4.0 and without the MAP adjuster my engine ran rich. With the MAP adjuster set at 4.25v, I have the A/F ratio just about perfect with excellent gas mileage and no pinging.
________________________________________________________________
- 1992 4.0 XJ Laredo UpCountry with modifications - 173k miles - AX15, NP231, D35c, D30
Estimated 240hp@5250rpm/280lbft@3500-4000rpm, 1/[email protected], race weight 3465lb
- Future mods -
4.6L stroker (under construction)
- Websites -
Jeep 4.0 performance, 4.6L stroker build-up
- Tech Webpages -
CTS resistor trick, Dual electric fans, IAT sensor relocation, Intake manifold heatshield, MAP adjuster, Oil temp. gauge install
- Info Pages -
Automotive formulae, Jeep 4.0 cam specs, Jeep engine dyno graphs
 
RichP said:
Just for laughs try another factory thermostat, it really should not fluctuate on the hiway at all but should remain rock steady at speed. How old is the fan clutch ??? The other question is how did you check your serp belt tension when you put it all back together. Most peoples 'feel' for the correct tension of 160lbs on a used belt is closer to 80lbs when actually checked with a krikit tension gauge..
Click to expand...


I forgot to mention: I replaced the fan clutch the same time I replaced the radiator so it's only about a month old.
I checked the belt tension by "feel" and also by reving it hard in idle, watching for slippage or squeeling. Everything looks ok there.
 
injectors

Dr. Dyno said:
No. Your stock injectors are already at the limit even without the MAP adjuster and with it, you're only trying to flog them even more.
It's better to get bigger injectors and, if necessary, try to lean them down rather than flogging smaller injectors.
I have Ford 24lb injectors on my 4.0 and without the MAP adjuster my engine ran rich. With the MAP adjuster set at 4.25v, I have the A/F ratio just about perfect with excellent gas mileage and no pinging.
Click to expand...

Thanks for the info, Dyno. I'll try some new injectors, along with a new FPR.

Where can I get ahold of an adjustable FPR? And the 24lb injectors?
Everyone seems to get Ford 24lb injectors - are there other preferred types available as well?
 
Actually an adjustable fuel pressure regulator might solve all you problems. Flow through any given injector is proportional to the square of the pressure. A small increase in pressure can yield a sizeable difference in injector flow. If your fuel pump is delivering what it should, you can crank up the pressure a couple of pounds to give your injectors a bit more headroom before being driven wide open. Adjustables are not real cheap though. Also, 210 is not overheating if everything else in the system is working properly. That is the temp that your engine is really designed to run at for the most part. The key is, does it stay at 210 under extreme conditions.
 
All 97+ XJs are designed to run at 210 degrees so your doing perfect.
 
Dont feel bad after doing the same thing Im in the same boat and to top it off I have a starting problem takes forever to crank over then just kind of sputters like its getting not enough fuel or too much and after 2 secs or so its great just like normal....It sounds like your in the same boat as me Im gonna try the MAT trick first if that doesnt help its either gonna have to be a map adj or a adj fuel pressure regulator from hesco(not cheap)....As this has turned out to be rather expensive for me I was just going to do the 99+ manifold swap and then a 62mm throttle body Ive spent about 300 including everthing so far plus whatever else I need to do yet...Im gonna check my pressure tonight with the vehicle off and on to see if Im getting enough pressure the Im going to give hesco a call on monday and talk to them and see what they suggest when I find out more Ill update here....
good luck
Ps for the record I say were both running reallly lean but its cool with me for this week or two Ive got emissions coming up after that gotta fix its just 2 damn hot in AZ for that....
 
themud said:
Dont feel bad after doing the same thing Im in the same boat and to top it off I have a starting problem takes forever to crank over then just kind of sputters like its getting not enough fuel or too much and after 2 secs or so its great just like normal....It sounds like your in the same boat as me Im gonna try the MAT trick first if that doesnt help its either gonna have to be a map adj or a adj fuel pressure regulator from hesco(not cheap)....As this has turned out to be rather expensive for me I was just going to do the 99+ manifold swap and then a 62mm throttle body Ive spent about 300 including everthing so far plus whatever else I need to do yet...Im gonna check my pressure tonight with the vehicle off and on to see if Im getting enough pressure the Im going to give hesco a call on monday and talk to them and see what they suggest when I find out more Ill update here....
good luck
Ps for the record I say were both running reallly lean but its cool with me for this week or two Ive got emissions coming up after that gotta fix its just 2 damn hot in AZ for that....
Click to expand...

Alright man let me know what Hesco suggests.

Anyway, to back up a little, I understand that it may be running hotter because its running too lean, but wouldn't the t-stat stay open longer to keep the temp down to make up for the extra heat? I would imagine this would in turn keep everything running in the same lower temps just as it was before the upgrades. Someone set me strait on this one.
 
Dr. Dyno said:
That's exactly what I was thinking. The engine's almost certainly running lean and if you find that the deposits on your plugs are whitish, that'll confirm it. You'll need a set of Ford 24lb injectors to correct the leanness.
In the event that the engine runs a little rich after installing these injectors (like mine did), you can install a MAP adjuster (it's easy to make one) to adjust the A/F ratio back to stoichiometric.
Click to expand...

Assuming I upgrade my injectors, is it also recommended to replace the fuel pressure regulator with a higher flow regulator? Say... 49lb? Or will the stock 39lb be sufficient?
 
XJVenom said:
Assuming I upgrade my injectors, is it also recommended to replace the fuel pressure regulator with a higher flow regulator? Say... 49lb? Or will the stock 39lb be sufficient?
Click to expand...

No it doesnt work that why the 96 and up obdII electronics put the regulator in the tank so youd have to replace the rail injectors and pump with one out of a 96 plus and I dont think its worth the cash as a new pump from the dealer runs 260 plus youd need a new rail as well not too hard to come by but still not cheap!!! Thats why Im looking at just the adj regulator to begin with...Id rather just go up 3 or 4 lbs on the regulator than try and tone down some 24lb injectors as Ive had mine pressure tested to 60psi and their still good :scared: ....We see I still gonna call tomorrow and see what hesco recommends....
let you know...
themud
 
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